Split GC.c, and move storage manager into sm/ directory

In preparation for parallel GC, split up the monolithic GC.c file into
smaller parts.  Also in this patch (and difficult to separate,
unfortunatley):
  
  - Don't include Stable.h in Rts.h, instead just include it where
    necessary.
  
  - consistently use STATIC_INLINE in source files, and INLINE_HEADER
    in header files.  STATIC_INLINE is now turned off when DEBUG is on,
    to make debugging easier.
  
  - The GC no longer takes the get_roots function as an argument.
    We weren't making use of this generalisation.

50 files changed, 5075 insertions, 4886 deletions

diff --git a/rts/Adjustor.c b/rts/Adjustor.c
index 4b042a17b2..8c950f79b4 100644
--- a/rts/Adjustor.c
+++ b/rts/Adjustor.c
@@ -41,6 +41,7 @@ Haskell side.
 #include "RtsExternal.h"
 #include "RtsUtils.h"
 #include "Storage.h"
+#include "Stable.h"
 #include <stdlib.h>
 
 #if defined(_WIN32)
diff --git a/rts/Arena.c b/rts/Arena.c
index 76ac23cf88..b2b5ce2d5a 100644
--- a/rts/Arena.c
+++ b/rts/Arena.c
@@ -20,7 +20,6 @@
 
 #include "Rts.h"
 #include "RtsUtils.h"
-#include "BlockAlloc.h"
 #include "Arena.h"
 
 #include <stdlib.h>
diff --git a/rts/Capability.c b/rts/Capability.c
index f1c625ef7c..1d282f0902 100644
--- a/rts/Capability.c
+++ b/rts/Capability.c
@@ -23,6 +23,7 @@
 #include "STM.h"
 #include "OSThreads.h"
 #include "Capability.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "Sparks.h"
 #include "Trace.h"
diff --git a/rts/Disassembler.c b/rts/Disassembler.c
index f29cce2daa..8777b81c43 100644
--- a/rts/Disassembler.c
+++ b/rts/Disassembler.c
@@ -16,6 +16,7 @@
 #include "RtsUtils.h"
 #include "Closures.h"
 #include "TSO.h"
+#include "Storage.h"
 #include "Schedule.h"
 
 #include "Bytecodes.h"
diff --git a/rts/GC.c b/rts/GC.c
deleted file mode 100644
index 4e8b3c2a26..0000000000
--- a/rts/GC.c
+++ /dev/null
@@ -1,4825 +0,0 @@
-/* -----------------------------------------------------------------------------
- *
- * (c) The GHC Team 1998-2003
- *
- * Generational garbage collector
- *
- * ---------------------------------------------------------------------------*/
-
-#include "PosixSource.h"
-#include "Rts.h"
-#include "RtsFlags.h"
-#include "RtsUtils.h"
-#include "Apply.h"
-#include "OSThreads.h"
-#include "Storage.h"
-#include "LdvProfile.h"
-#include "Updates.h"
-#include "Stats.h"
-#include "Schedule.h"
-#include "Sanity.h"
-#include "BlockAlloc.h"
-#include "MBlock.h"
-#include "ProfHeap.h"
-#include "SchedAPI.h"
-#include "Weak.h"
-#include "Prelude.h"
-#include "ParTicky.h"		// ToDo: move into Rts.h
-#include "GCCompact.h"
-#include "RtsSignals.h"
-#include "STM.h"
-#if defined(GRAN) || defined(PAR)
-# include "GranSimRts.h"
-# include "ParallelRts.h"
-# include "FetchMe.h"
-# if defined(DEBUG)
-#  include "Printer.h"
-#  include "ParallelDebug.h"
-# endif
-#endif
-#include "HsFFI.h"
-#include "Linker.h"
-#if defined(RTS_GTK_FRONTPANEL)
-#include "FrontPanel.h"
-#endif
-#include "Trace.h"
-#include "RetainerProfile.h"
-#include "RaiseAsync.h"
-
-#include <string.h>
-
-// Turn off inlining when debugging - it obfuscates things
-#ifdef DEBUG
-# undef  STATIC_INLINE
-# define STATIC_INLINE static
-#endif
-
-/* STATIC OBJECT LIST.
- *
- * During GC:
- * We maintain a linked list of static objects that are still live.
- * The requirements for this list are:
- *
- *  - we need to scan the list while adding to it, in order to
- *    scavenge all the static objects (in the same way that
- *    breadth-first scavenging works for dynamic objects).
- *
- *  - we need to be able to tell whether an object is already on
- *    the list, to break loops.
- *
- * Each static object has a "static link field", which we use for
- * linking objects on to the list.  We use a stack-type list, consing
- * objects on the front as they are added (this means that the
- * scavenge phase is depth-first, not breadth-first, but that
- * shouldn't matter).  
- *
- * A separate list is kept for objects that have been scavenged
- * already - this is so that we can zero all the marks afterwards.
- *
- * An object is on the list if its static link field is non-zero; this
- * means that we have to mark the end of the list with '1', not NULL.  
- *
- * Extra notes for generational GC:
- *
- * Each generation has a static object list associated with it.  When
- * collecting generations up to N, we treat the static object lists
- * from generations > N as roots.
- *
- * We build up a static object list while collecting generations 0..N,
- * which is then appended to the static object list of generation N+1.
- */
-static StgClosure* static_objects;      // live static objects
-StgClosure* scavenged_static_objects;   // static objects scavenged so far
-
-/* N is the oldest generation being collected, where the generations
- * are numbered starting at 0.  A major GC (indicated by the major_gc
- * flag) is when we're collecting all generations.  We only attempt to
- * deal with static objects and GC CAFs when doing a major GC.
- */
-static nat N;
-static rtsBool major_gc;
-
-/* Youngest generation that objects should be evacuated to in
- * evacuate().  (Logically an argument to evacuate, but it's static
- * a lot of the time so we optimise it into a global variable).
- */
-static nat evac_gen;
-
-/* Whether to do eager promotion or not.
- */
-static rtsBool eager_promotion;
-
-/* Weak pointers
- */
-StgWeak *old_weak_ptr_list; // also pending finaliser list
-
-/* Which stage of processing various kinds of weak pointer are we at?
- * (see traverse_weak_ptr_list() below for discussion).
- */
-typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
-static WeakStage weak_stage;
-
-/* List of all threads during GC
- */
-static StgTSO *old_all_threads;
-StgTSO *resurrected_threads;
-
-/* Flag indicating failure to evacuate an object to the desired
- * generation.
- */
-static rtsBool failed_to_evac;
-
-/* Saved nursery (used for 2-space collector only)
- */
-static bdescr *saved_nursery;
-static nat saved_n_blocks;
-  
-/* Data used for allocation area sizing.
- */
-static lnat new_blocks;		 // blocks allocated during this GC 
-static lnat new_scavd_blocks;	 // ditto, but depth-first blocks
-static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC 
-
-/* Used to avoid long recursion due to selector thunks
- */
-static lnat thunk_selector_depth = 0;
-#define MAX_THUNK_SELECTOR_DEPTH 8
-
-/* Mut-list stats */
-#ifdef DEBUG
-static nat 
-    mutlist_MUTVARS,
-    mutlist_MUTARRS,
-    mutlist_OTHERS;
-#endif
-
-/* -----------------------------------------------------------------------------
-   Static function declarations
-   -------------------------------------------------------------------------- */
-
-static bdescr *     gc_alloc_block          ( step *stp );
-static void         mark_root               ( StgClosure **root );
-
-// Use a register argument for evacuate, if available.
-#if __GNUC__ >= 2
-#define REGPARM1 __attribute__((regparm(1)))
-#else
-#define REGPARM1
-#endif
-
-REGPARM1 static StgClosure * evacuate (StgClosure *q);
-
-static void         zero_static_object_list ( StgClosure* first_static );
-
-static rtsBool      traverse_weak_ptr_list  ( void );
-static void         mark_weak_ptr_list      ( StgWeak **list );
-static rtsBool      traverse_blackhole_queue ( void );
-
-static StgClosure * eval_thunk_selector     ( nat field, StgSelector * p );
-
-
-static void    scavenge                ( step * );
-static void    scavenge_mark_stack     ( void );
-static void    scavenge_stack          ( StgPtr p, StgPtr stack_end );
-static rtsBool scavenge_one            ( StgPtr p );
-static void    scavenge_large          ( step * );
-static void    scavenge_static         ( void );
-static void    scavenge_mutable_list   ( generation *g );
-
-static void    scavenge_large_bitmap   ( StgPtr p, 
-					 StgLargeBitmap *large_bitmap, 
-					 nat size );
-
-#if 0 && defined(DEBUG)
-static void         gcCAFs                  ( void );
-#endif
-
-/* -----------------------------------------------------------------------------
-   inline functions etc. for dealing with the mark bitmap & stack.
-   -------------------------------------------------------------------------- */
-
-#define MARK_STACK_BLOCKS 4
-
-static bdescr *mark_stack_bdescr;
-static StgPtr *mark_stack;
-static StgPtr *mark_sp;
-static StgPtr *mark_splim;
-
-// Flag and pointers used for falling back to a linear scan when the
-// mark stack overflows.
-static rtsBool mark_stack_overflowed;
-static bdescr *oldgen_scan_bd;
-static StgPtr  oldgen_scan;
-
-STATIC_INLINE rtsBool
-mark_stack_empty(void)
-{
-    return mark_sp == mark_stack;
-}
-
-STATIC_INLINE rtsBool
-mark_stack_full(void)
-{
-    return mark_sp >= mark_splim;
-}
-
-STATIC_INLINE void
-reset_mark_stack(void)
-{
-    mark_sp = mark_stack;
-}
-
-STATIC_INLINE void
-push_mark_stack(StgPtr p)
-{
-    *mark_sp++ = p;
-}
-
-STATIC_INLINE StgPtr
-pop_mark_stack(void)
-{
-    return *--mark_sp;
-}
-
-/* -----------------------------------------------------------------------------
-   Allocate a new to-space block in the given step.
-   -------------------------------------------------------------------------- */
-
-static bdescr *
-gc_alloc_block(step *stp)
-{
-    bdescr *bd = allocBlock();
-    bd->gen_no = stp->gen_no;
-    bd->step = stp;
-    bd->link = NULL;
-
-    // blocks in to-space in generations up to and including N
-    // get the BF_EVACUATED flag.
-    if (stp->gen_no <= N) {
-	bd->flags = BF_EVACUATED;
-    } else {
-	bd->flags = 0;
-    }
-
-    // Start a new to-space block, chain it on after the previous one.
-    if (stp->hp_bd != NULL) {
-	stp->hp_bd->free = stp->hp;
-	stp->hp_bd->link = bd;
-    }
-
-    stp->hp_bd = bd;
-    stp->hp    = bd->start;
-    stp->hpLim = stp->hp + BLOCK_SIZE_W;
-
-    stp->n_blocks++;
-    new_blocks++;
-
-    return bd;
-}
-
-static bdescr *
-gc_alloc_scavd_block(step *stp)
-{
-    bdescr *bd = allocBlock();
-    bd->gen_no = stp->gen_no;
-    bd->step = stp;
-
-    // blocks in to-space in generations up to and including N
-    // get the BF_EVACUATED flag.
-    if (stp->gen_no <= N) {
-	bd->flags = BF_EVACUATED;
-    } else {
-	bd->flags = 0;
-    }
-
-    bd->link = stp->blocks;
-    stp->blocks = bd;
-
-    if (stp->scavd_hp != NULL) {
-	Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
-    }
-    stp->scavd_hp    = bd->start;
-    stp->scavd_hpLim = stp->scavd_hp + BLOCK_SIZE_W;
-
-    stp->n_blocks++;
-    new_scavd_blocks++;
-
-    return bd;
-}
-
-/* -----------------------------------------------------------------------------
-   GarbageCollect
-
-   Rough outline of the algorithm: for garbage collecting generation N
-   (and all younger generations):
-
-     - follow all pointers in the root set.  the root set includes all 
-       mutable objects in all generations (mutable_list).
-
-     - for each pointer, evacuate the object it points to into either
-
-       + to-space of the step given by step->to, which is the next
-         highest step in this generation or the first step in the next
-         generation if this is the last step.
-
-       + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
-         When we evacuate an object we attempt to evacuate
-         everything it points to into the same generation - this is
-         achieved by setting evac_gen to the desired generation.  If
-         we can't do this, then an entry in the mut list has to
-         be made for the cross-generation pointer.
-
-       + if the object is already in a generation > N, then leave
-         it alone.
-
-     - repeatedly scavenge to-space from each step in each generation
-       being collected until no more objects can be evacuated.
-      
-     - free from-space in each step, and set from-space = to-space.
-
-   Locks held: all capabilities are held throughout GarbageCollect().
-
-   -------------------------------------------------------------------------- */
-
-void
-GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
-{
-  bdescr *bd;
-  step *stp;
-  lnat live, allocated, copied = 0, scavd_copied = 0;
-  lnat oldgen_saved_blocks = 0;
-  nat g, s, i;
-
-  ACQUIRE_SM_LOCK;
-
-#ifdef PROFILING
-  CostCentreStack *prev_CCS;
-#endif
-
-  debugTrace(DEBUG_gc, "starting GC");
-
-#if defined(RTS_USER_SIGNALS)
-  // block signals
-  blockUserSignals();
-#endif
-
-  // tell the STM to discard any cached closures its hoping to re-use
-  stmPreGCHook();
-
-  // tell the stats department that we've started a GC 
-  stat_startGC();
-
-#ifdef DEBUG
-  // check for memory leaks if DEBUG is on 
-  memInventory();
-#endif
-
-#ifdef DEBUG
-  mutlist_MUTVARS = 0;
-  mutlist_MUTARRS = 0;
-  mutlist_OTHERS = 0;
-#endif
-
-  // Init stats and print par specific (timing) info 
-  PAR_TICKY_PAR_START();
-
-  // attribute any costs to CCS_GC 
-#ifdef PROFILING
-  prev_CCS = CCCS;
-  CCCS = CCS_GC;
-#endif
-
-  /* Approximate how much we allocated.  
-   * Todo: only when generating stats? 
-   */
-  allocated = calcAllocated();
-
-  /* Figure out which generation to collect
-   */
-  if (force_major_gc) {
-    N = RtsFlags.GcFlags.generations - 1;
-    major_gc = rtsTrue;
-  } else {
-    N = 0;
-    for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
-      if (generations[g].steps[0].n_blocks +
-	  generations[g].steps[0].n_large_blocks
-	  >= generations[g].max_blocks) {
-        N = g;
-      }
-    }
-    major_gc = (N == RtsFlags.GcFlags.generations-1);
-  }
-
-#ifdef RTS_GTK_FRONTPANEL
-  if (RtsFlags.GcFlags.frontpanel) {
-      updateFrontPanelBeforeGC(N);
-  }
-#endif
-
-  // check stack sanity *before* GC (ToDo: check all threads) 
-#if defined(GRAN)
-  // ToDo!: check sanity  IF_DEBUG(sanity, checkTSOsSanity());
-#endif
-  IF_DEBUG(sanity, checkFreeListSanity());
-
-  /* Initialise the static object lists
-   */
-  static_objects = END_OF_STATIC_LIST;
-  scavenged_static_objects = END_OF_STATIC_LIST;
-
-  /* Save the nursery if we're doing a two-space collection.
-   * g0s0->blocks will be used for to-space, so we need to get the
-   * nursery out of the way.
-   */
-  if (RtsFlags.GcFlags.generations == 1) {
-      saved_nursery = g0s0->blocks;
-      saved_n_blocks = g0s0->n_blocks;
-      g0s0->blocks = NULL;
-      g0s0->n_blocks = 0;
-  }
-
-  /* Keep a count of how many new blocks we allocated during this GC
-   * (used for resizing the allocation area, later).
-   */
-  new_blocks = 0;
-  new_scavd_blocks = 0;
-
-  // Initialise to-space in all the generations/steps that we're
-  // collecting.
-  //
-  for (g = 0; g <= N; g++) {
-
-    // throw away the mutable list.  Invariant: the mutable list
-    // always has at least one block; this means we can avoid a check for
-    // NULL in recordMutable().
-    if (g != 0) {
-	freeChain(generations[g].mut_list);
-	generations[g].mut_list = allocBlock();
-	for (i = 0; i < n_capabilities; i++) {
-	    freeChain(capabilities[i].mut_lists[g]);
-	    capabilities[i].mut_lists[g] = allocBlock();
-	}
-    }
-
-    for (s = 0; s < generations[g].n_steps; s++) {
-
-      // generation 0, step 0 doesn't need to-space 
-      if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) { 
-	continue; 
-      }
-
-      stp = &generations[g].steps[s];
-      ASSERT(stp->gen_no == g);
-
-      // start a new to-space for this step.
-      stp->old_blocks   = stp->blocks;
-      stp->n_old_blocks = stp->n_blocks;
-
-      // allocate the first to-space block; extra blocks will be
-      // chained on as necessary.
-      stp->hp_bd     = NULL;
-      bd = gc_alloc_block(stp);
-      stp->blocks      = bd;
-      stp->n_blocks    = 1;
-      stp->scan        = bd->start;
-      stp->scan_bd     = bd;
-
-      // allocate a block for "already scavenged" objects.  This goes
-      // on the front of the stp->blocks list, so it won't be
-      // traversed by the scavenging sweep.
-      gc_alloc_scavd_block(stp);
-
-      // initialise the large object queues.
-      stp->new_large_objects = NULL;
-      stp->scavenged_large_objects = NULL;
-      stp->n_scavenged_large_blocks = 0;
-
-      // mark the large objects as not evacuated yet 
-      for (bd = stp->large_objects; bd; bd = bd->link) {
-	bd->flags &= ~BF_EVACUATED;
-      }
-
-      // for a compacted step, we need to allocate the bitmap
-      if (stp->is_compacted) {
-	  nat bitmap_size; // in bytes
-	  bdescr *bitmap_bdescr;
-	  StgWord *bitmap;
-
-	  bitmap_size = stp->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
-
-	  if (bitmap_size > 0) {
-	      bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size) 
-					 / BLOCK_SIZE);
-	      stp->bitmap = bitmap_bdescr;
-	      bitmap = bitmap_bdescr->start;
-	      
-	      debugTrace(DEBUG_gc, "bitmap_size: %d, bitmap: %p",
-			 bitmap_size, bitmap);
-	      
-	      // don't forget to fill it with zeros!
-	      memset(bitmap, 0, bitmap_size);
-	      
-	      // For each block in this step, point to its bitmap from the
-	      // block descriptor.
-	      for (bd=stp->old_blocks; bd != NULL; bd = bd->link) {
-		  bd->u.bitmap = bitmap;
-		  bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
-
-		  // Also at this point we set the BF_COMPACTED flag
-		  // for this block.  The invariant is that
-		  // BF_COMPACTED is always unset, except during GC
-		  // when it is set on those blocks which will be
-		  // compacted.
-		  bd->flags |= BF_COMPACTED;
-	      }
-	  }
-      }
-    }
-  }
-
-  /* make sure the older generations have at least one block to
-   * allocate into (this makes things easier for copy(), see below).
-   */
-  for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
-    for (s = 0; s < generations[g].n_steps; s++) {
-      stp = &generations[g].steps[s];
-      if (stp->hp_bd == NULL) {
-	  ASSERT(stp->blocks == NULL);
-	  bd = gc_alloc_block(stp);
-	  stp->blocks = bd;
-	  stp->n_blocks = 1;
-      }
-      if (stp->scavd_hp == NULL) {
-	  gc_alloc_scavd_block(stp);
-	  stp->n_blocks++;
-      }
-      /* Set the scan pointer for older generations: remember we
-       * still have to scavenge objects that have been promoted. */
-      stp->scan = stp->hp;
-      stp->scan_bd = stp->hp_bd;
-      stp->new_large_objects = NULL;
-      stp->scavenged_large_objects = NULL;
-      stp->n_scavenged_large_blocks = 0;
-    }
-
-    /* Move the private mutable lists from each capability onto the
-     * main mutable list for the generation.
-     */
-    for (i = 0; i < n_capabilities; i++) {
-	for (bd = capabilities[i].mut_lists[g]; 
-	     bd->link != NULL; bd = bd->link) {
-	    /* nothing */
-	}
-	bd->link = generations[g].mut_list;
-	generations[g].mut_list = capabilities[i].mut_lists[g];
-	capabilities[i].mut_lists[g] = allocBlock();
-    }
-  }
-
-  /* Allocate a mark stack if we're doing a major collection.
-   */
-  if (major_gc) {
-      mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
-      mark_stack = (StgPtr *)mark_stack_bdescr->start;
-      mark_sp    = mark_stack;
-      mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
-  } else {
-      mark_stack_bdescr = NULL;
-  }
-
-  eager_promotion = rtsTrue; // for now
-
-  /* -----------------------------------------------------------------------
-   * follow all the roots that we know about:
-   *   - mutable lists from each generation > N
-   * we want to *scavenge* these roots, not evacuate them: they're not
-   * going to move in this GC.
-   * Also: do them in reverse generation order.  This is because we
-   * often want to promote objects that are pointed to by older
-   * generations early, so we don't have to repeatedly copy them.
-   * Doing the generations in reverse order ensures that we don't end
-   * up in the situation where we want to evac an object to gen 3 and
-   * it has already been evaced to gen 2.
-   */
-  { 
-    int st;
-    for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
-      generations[g].saved_mut_list = generations[g].mut_list;
-      generations[g].mut_list = allocBlock(); 
-        // mut_list always has at least one block.
-    }
-
-    for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
-      IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
-      scavenge_mutable_list(&generations[g]);
-      evac_gen = g;
-      for (st = generations[g].n_steps-1; st >= 0; st--) {
-	scavenge(&generations[g].steps[st]);
-      }
-    }
-  }
-
-  /* follow roots from the CAF list (used by GHCi)
-   */
-  evac_gen = 0;
-  markCAFs(mark_root);
-
-  /* follow all the roots that the application knows about.
-   */
-  evac_gen = 0;
-  get_roots(mark_root);
-
-#if defined(PAR)
-  /* And don't forget to mark the TSO if we got here direct from
-   * Haskell! */
-  /* Not needed in a seq version?
-  if (CurrentTSO) {
-    CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
-  }
-  */
-
-  // Mark the entries in the GALA table of the parallel system 
-  markLocalGAs(major_gc);
-  // Mark all entries on the list of pending fetches 
-  markPendingFetches(major_gc);
-#endif
-
-  /* Mark the weak pointer list, and prepare to detect dead weak
-   * pointers.
-   */
-  mark_weak_ptr_list(&weak_ptr_list);
-  old_weak_ptr_list = weak_ptr_list;
-  weak_ptr_list = NULL;
-  weak_stage = WeakPtrs;
-
-  /* The all_threads list is like the weak_ptr_list.  
-   * See traverse_weak_ptr_list() for the details.
-   */
-  old_all_threads = all_threads;
-  all_threads = END_TSO_QUEUE;
-  resurrected_threads = END_TSO_QUEUE;
-
-  /* Mark the stable pointer table.
-   */
-  markStablePtrTable(mark_root);
-
-  /* Mark the root pointer table.
-   */
-  markRootPtrTable(mark_root);
-
-  /* -------------------------------------------------------------------------
-   * Repeatedly scavenge all the areas we know about until there's no
-   * more scavenging to be done.
-   */
-  { 
-    rtsBool flag;
-  loop:
-    flag = rtsFalse;
-
-    // scavenge static objects 
-    if (major_gc && static_objects != END_OF_STATIC_LIST) {
-	IF_DEBUG(sanity, checkStaticObjects(static_objects));
-	scavenge_static();
-    }
-
-    /* When scavenging the older generations:  Objects may have been
-     * evacuated from generations <= N into older generations, and we
-     * need to scavenge these objects.  We're going to try to ensure that
-     * any evacuations that occur move the objects into at least the
-     * same generation as the object being scavenged, otherwise we
-     * have to create new entries on the mutable list for the older
-     * generation.
-     */
-
-    // scavenge each step in generations 0..maxgen 
-    { 
-      long gen;
-      int st; 
-
-    loop2:
-      // scavenge objects in compacted generation
-      if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
-	  (mark_stack_bdescr != NULL && !mark_stack_empty())) {
-	  scavenge_mark_stack();
-	  flag = rtsTrue;
-      }
-
-      for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
-	for (st = generations[gen].n_steps; --st >= 0; ) {
-	  if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) { 
-	    continue; 
-	  }
-	  stp = &generations[gen].steps[st];
-	  evac_gen = gen;
-	  if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
-	    scavenge(stp);
-	    flag = rtsTrue;
-	    goto loop2;
-	  }
-	  if (stp->new_large_objects != NULL) {
-	    scavenge_large(stp);
-	    flag = rtsTrue;
-	    goto loop2;
-	  }
-	}
-      }
-    }
-
-    // if any blackholes are alive, make the threads that wait on
-    // them alive too.
-    if (traverse_blackhole_queue())
-	flag = rtsTrue;
-
-    if (flag) { goto loop; }
-
-    // must be last...  invariant is that everything is fully
-    // scavenged at this point.
-    if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something 
-      goto loop;
-    }
-  }
-
-  /* Update the pointers from the task list - these are
-   * treated as weak pointers because we want to allow a main thread
-   * to get a BlockedOnDeadMVar exception in the same way as any other
-   * thread.  Note that the threads should all have been retained by
-   * GC by virtue of being on the all_threads list, we're just
-   * updating pointers here.
-   */
-  {
-      Task *task;
-      StgTSO *tso;
-      for (task = all_tasks; task != NULL; task = task->all_link) {
-	  if (!task->stopped && task->tso) {
-	      ASSERT(task->tso->bound == task);
-	      tso = (StgTSO *) isAlive((StgClosure *)task->tso);
-	      if (tso == NULL) {
-		  barf("task %p: main thread %d has been GC'd", 
-#ifdef THREADED_RTS
-		       (void *)task->id, 
-#else
-		       (void *)task,
-#endif
-		       task->tso->id);
-	      }
-	      task->tso = tso;
-	  }
-      }
-  }
-
-#if defined(PAR)
-  // Reconstruct the Global Address tables used in GUM 
-  rebuildGAtables(major_gc);
-  IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
-#endif
-
-  // Now see which stable names are still alive.
-  gcStablePtrTable();
-
-  // Tidy the end of the to-space chains 
-  for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
-      for (s = 0; s < generations[g].n_steps; s++) {
-	  stp = &generations[g].steps[s];
-	  if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
-	      ASSERT(Bdescr(stp->hp) == stp->hp_bd);
-	      stp->hp_bd->free = stp->hp;
-	      Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
-	  }
-      }
-  }
-
-#ifdef PROFILING
-  // We call processHeapClosureForDead() on every closure destroyed during
-  // the current garbage collection, so we invoke LdvCensusForDead().
-  if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
-      || RtsFlags.ProfFlags.bioSelector != NULL)
-    LdvCensusForDead(N);
-#endif
-
-  // NO MORE EVACUATION AFTER THIS POINT!
-  // Finally: compaction of the oldest generation.
-  if (major_gc && oldest_gen->steps[0].is_compacted) {
-      // save number of blocks for stats
-      oldgen_saved_blocks = oldest_gen->steps[0].n_old_blocks;
-      compact(get_roots);
-  }
-
-  IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
-
-  /* run through all the generations/steps and tidy up 
-   */
-  copied = new_blocks * BLOCK_SIZE_W;
-  scavd_copied =  new_scavd_blocks * BLOCK_SIZE_W;
-  for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
-
-    if (g <= N) {
-      generations[g].collections++; // for stats 
-    }
-
-    // Count the mutable list as bytes "copied" for the purposes of
-    // stats.  Every mutable list is copied during every GC.
-    if (g > 0) {
-	nat mut_list_size = 0;
-	for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
-	    mut_list_size += bd->free - bd->start;
-	}
-	copied +=  mut_list_size;
-
-	debugTrace(DEBUG_gc,
-		   "mut_list_size: %lu (%d vars, %d arrays, %d others)",
-		   (unsigned long)(mut_list_size * sizeof(W_)),
-		   mutlist_MUTVARS, mutlist_MUTARRS, mutlist_OTHERS);
-    }
-
-    for (s = 0; s < generations[g].n_steps; s++) {
-      bdescr *next;
-      stp = &generations[g].steps[s];
-
-      if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
-	// stats information: how much we copied 
-	if (g <= N) {
-	  copied -= stp->hp_bd->start + BLOCK_SIZE_W -
-	    stp->hp_bd->free;
-	  scavd_copied -= (P_)(BLOCK_ROUND_UP(stp->scavd_hp)) - stp->scavd_hp;
-	}
-      }
-
-      // for generations we collected... 
-      if (g <= N) {
-
-	/* free old memory and shift to-space into from-space for all
-	 * the collected steps (except the allocation area).  These
-	 * freed blocks will probaby be quickly recycled.
-	 */
-	if (!(g == 0 && s == 0)) {
-	    if (stp->is_compacted) {
-		// for a compacted step, just shift the new to-space
-		// onto the front of the now-compacted existing blocks.
-		for (bd = stp->blocks; bd != NULL; bd = bd->link) {
-		    bd->flags &= ~BF_EVACUATED;  // now from-space 
-		}
-		// tack the new blocks on the end of the existing blocks
-		if (stp->old_blocks != NULL) {
-		    for (bd = stp->old_blocks; bd != NULL; bd = next) {
-			// NB. this step might not be compacted next
-			// time, so reset the BF_COMPACTED flags.
-			// They are set before GC if we're going to
-			// compact.  (search for BF_COMPACTED above).
-			bd->flags &= ~BF_COMPACTED;
-			next = bd->link;
-			if (next == NULL) {
-			    bd->link = stp->blocks;
-			}
-		    }
-		    stp->blocks = stp->old_blocks;
-		}
-		// add the new blocks to the block tally
-		stp->n_blocks += stp->n_old_blocks;
-		ASSERT(countBlocks(stp->blocks) == stp->n_blocks);
-	    } else {
-		freeChain(stp->old_blocks);
-		for (bd = stp->blocks; bd != NULL; bd = bd->link) {
-		    bd->flags &= ~BF_EVACUATED;	 // now from-space 
-		}
-	    }
-	    stp->old_blocks = NULL;
-	    stp->n_old_blocks = 0;
-	}
-
-	/* LARGE OBJECTS.  The current live large objects are chained on
-	 * scavenged_large, having been moved during garbage
-	 * collection from large_objects.  Any objects left on
-	 * large_objects list are therefore dead, so we free them here.
-	 */
-	for (bd = stp->large_objects; bd != NULL; bd = next) {
-	  next = bd->link;
-	  freeGroup(bd);
-	  bd = next;
-	}
-
-	// update the count of blocks used by large objects
-	for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
-	  bd->flags &= ~BF_EVACUATED;
-	}
-	stp->large_objects  = stp->scavenged_large_objects;
-	stp->n_large_blocks = stp->n_scavenged_large_blocks;
-
-      } else {
-	// for older generations... 
-	
-	/* For older generations, we need to append the
-	 * scavenged_large_object list (i.e. large objects that have been
-	 * promoted during this GC) to the large_object list for that step.
-	 */
-	for (bd = stp->scavenged_large_objects; bd; bd = next) {
-	  next = bd->link;
-	  bd->flags &= ~BF_EVACUATED;
-	  dbl_link_onto(bd, &stp->large_objects);
-	}
-
-	// add the new blocks we promoted during this GC 
-	stp->n_large_blocks += stp->n_scavenged_large_blocks;
-      }
-    }
-  }
-
-  /* Reset the sizes of the older generations when we do a major
-   * collection.
-   *
-   * CURRENT STRATEGY: make all generations except zero the same size.
-   * We have to stay within the maximum heap size, and leave a certain
-   * percentage of the maximum heap size available to allocate into.
-   */
-  if (major_gc && RtsFlags.GcFlags.generations > 1) {
-      nat live, size, min_alloc;
-      nat max  = RtsFlags.GcFlags.maxHeapSize;
-      nat gens = RtsFlags.GcFlags.generations;
-
-      // live in the oldest generations
-      live = oldest_gen->steps[0].n_blocks +
-	     oldest_gen->steps[0].n_large_blocks;
-
-      // default max size for all generations except zero
-      size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
-		     RtsFlags.GcFlags.minOldGenSize);
-
-      // minimum size for generation zero
-      min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
-			  RtsFlags.GcFlags.minAllocAreaSize);
-
-      // Auto-enable compaction when the residency reaches a
-      // certain percentage of the maximum heap size (default: 30%).
-      if (RtsFlags.GcFlags.generations > 1 &&
-	  (RtsFlags.GcFlags.compact ||
-	   (max > 0 &&
-	    oldest_gen->steps[0].n_blocks > 
-	    (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
-	  oldest_gen->steps[0].is_compacted = 1;
-//	  debugBelch("compaction: on\n", live);
-      } else {
-	  oldest_gen->steps[0].is_compacted = 0;
-//	  debugBelch("compaction: off\n", live);
-      }
-
-      // if we're going to go over the maximum heap size, reduce the
-      // size of the generations accordingly.  The calculation is
-      // different if compaction is turned on, because we don't need
-      // to double the space required to collect the old generation.
-      if (max != 0) {
-
-	  // this test is necessary to ensure that the calculations
-	  // below don't have any negative results - we're working
-	  // with unsigned values here.
-	  if (max < min_alloc) {
-	      heapOverflow();
-	  }
-
-	  if (oldest_gen->steps[0].is_compacted) {
-	      if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
-		  size = (max - min_alloc) / ((gens - 1) * 2 - 1);
-	      }
-	  } else {
-	      if ( (size * (gens - 1) * 2) + min_alloc > max ) {
-		  size = (max - min_alloc) / ((gens - 1) * 2);
-	      }
-	  }
-
-	  if (size < live) {
-	      heapOverflow();
-	  }
-      }
-
-#if 0
-      debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
-	      min_alloc, size, max);
-#endif
-
-      for (g = 0; g < gens; g++) {
-	  generations[g].max_blocks = size;
-      }
-  }
-
-  // Guess the amount of live data for stats.
-  live = calcLive();
-
-  /* Free the small objects allocated via allocate(), since this will
-   * all have been copied into G0S1 now.  
-   */
-  if (small_alloc_list != NULL) {
-    freeChain(small_alloc_list);
-  }
-  small_alloc_list = NULL;
-  alloc_blocks = 0;
-  alloc_Hp = NULL;
-  alloc_HpLim = NULL;
-  alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
-
-  // Start a new pinned_object_block
-  pinned_object_block = NULL;
-
-  /* Free the mark stack.
-   */
-  if (mark_stack_bdescr != NULL) {
-      freeGroup(mark_stack_bdescr);
-  }
-
-  /* Free any bitmaps.
-   */
-  for (g = 0; g <= N; g++) {
-      for (s = 0; s < generations[g].n_steps; s++) {
-	  stp = &generations[g].steps[s];
-	  if (stp->bitmap != NULL) {
-	      freeGroup(stp->bitmap);
-	      stp->bitmap = NULL;
-	  }
-      }
-  }
-
-  /* Two-space collector:
-   * Free the old to-space, and estimate the amount of live data.
-   */
-  if (RtsFlags.GcFlags.generations == 1) {
-    nat blocks;
-    
-    if (g0s0->old_blocks != NULL) {
-      freeChain(g0s0->old_blocks);
-    }
-    for (bd = g0s0->blocks; bd != NULL; bd = bd->link) {
-      bd->flags = 0;	// now from-space 
-    }
-    g0s0->old_blocks = g0s0->blocks;
-    g0s0->n_old_blocks = g0s0->n_blocks;
-    g0s0->blocks = saved_nursery;
-    g0s0->n_blocks = saved_n_blocks;
-
-    /* For a two-space collector, we need to resize the nursery. */
-    
-    /* set up a new nursery.  Allocate a nursery size based on a
-     * function of the amount of live data (by default a factor of 2)
-     * Use the blocks from the old nursery if possible, freeing up any
-     * left over blocks.
-     *
-     * If we get near the maximum heap size, then adjust our nursery
-     * size accordingly.  If the nursery is the same size as the live
-     * data (L), then we need 3L bytes.  We can reduce the size of the
-     * nursery to bring the required memory down near 2L bytes.
-     * 
-     * A normal 2-space collector would need 4L bytes to give the same
-     * performance we get from 3L bytes, reducing to the same
-     * performance at 2L bytes.
-     */
-    blocks = g0s0->n_old_blocks;
-
-    if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
-	 blocks * RtsFlags.GcFlags.oldGenFactor * 2 > 
-	   RtsFlags.GcFlags.maxHeapSize ) {
-      long adjusted_blocks;  // signed on purpose 
-      int pc_free; 
-      
-      adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
-
-      debugTrace(DEBUG_gc, "near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", 
-		 RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks);
-
-      pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
-      if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
-	heapOverflow();
-      }
-      blocks = adjusted_blocks;
-      
-    } else {
-      blocks *= RtsFlags.GcFlags.oldGenFactor;
-      if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
-	blocks = RtsFlags.GcFlags.minAllocAreaSize;
-      }
-    }
-    resizeNurseries(blocks);
-    
-  } else {
-    /* Generational collector:
-     * If the user has given us a suggested heap size, adjust our
-     * allocation area to make best use of the memory available.
-     */
-
-    if (RtsFlags.GcFlags.heapSizeSuggestion) {
-      long blocks;
-      nat needed = calcNeeded(); 	// approx blocks needed at next GC 
-
-      /* Guess how much will be live in generation 0 step 0 next time.
-       * A good approximation is obtained by finding the
-       * percentage of g0s0 that was live at the last minor GC.
-       */
-      if (N == 0) {
-	g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
-      }
-
-      /* Estimate a size for the allocation area based on the
-       * information available.  We might end up going slightly under
-       * or over the suggested heap size, but we should be pretty
-       * close on average.
-       *
-       * Formula:            suggested - needed
-       *                ----------------------------
-       *                    1 + g0s0_pcnt_kept/100
-       *
-       * where 'needed' is the amount of memory needed at the next
-       * collection for collecting all steps except g0s0.
-       */
-      blocks = 
-	(((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
-	(100 + (long)g0s0_pcnt_kept);
-      
-      if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
-	blocks = RtsFlags.GcFlags.minAllocAreaSize;
-      }
-      
-      resizeNurseries((nat)blocks);
-
-    } else {
-      // we might have added extra large blocks to the nursery, so
-      // resize back to minAllocAreaSize again.
-      resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
-    }
-  }
-
- // mark the garbage collected CAFs as dead 
-#if 0 && defined(DEBUG) // doesn't work at the moment 
-  if (major_gc) { gcCAFs(); }
-#endif
-  
-#ifdef PROFILING
-  // resetStaticObjectForRetainerProfiling() must be called before
-  // zeroing below.
-  resetStaticObjectForRetainerProfiling();
-#endif
-
-  // zero the scavenged static object list 
-  if (major_gc) {
-    zero_static_object_list(scavenged_static_objects);
-  }
-
-  // Reset the nursery
-  resetNurseries();
-
-  // start any pending finalizers 
-  RELEASE_SM_LOCK;
-  scheduleFinalizers(last_free_capability, old_weak_ptr_list);
-  ACQUIRE_SM_LOCK;
-  
-  // send exceptions to any threads which were about to die 
-  RELEASE_SM_LOCK;
-  resurrectThreads(resurrected_threads);
-  ACQUIRE_SM_LOCK;
-
-  // Update the stable pointer hash table.
-  updateStablePtrTable(major_gc);
-
-  // check sanity after GC 
-  IF_DEBUG(sanity, checkSanity());
-
-  // extra GC trace info 
-  IF_DEBUG(gc, statDescribeGens());
-
-#ifdef DEBUG
-  // symbol-table based profiling 
-  /*  heapCensus(to_blocks); */ /* ToDo */
-#endif
-
-  // restore enclosing cost centre 
-#ifdef PROFILING
-  CCCS = prev_CCS;
-#endif
-
-#ifdef DEBUG
-  // check for memory leaks if DEBUG is on 
-  memInventory();
-#endif
-
-#ifdef RTS_GTK_FRONTPANEL
-  if (RtsFlags.GcFlags.frontpanel) {
-      updateFrontPanelAfterGC( N, live );
-  }
-#endif
-
-  // ok, GC over: tell the stats department what happened. 
-  stat_endGC(allocated, live, copied, scavd_copied, N);
-
-#if defined(RTS_USER_SIGNALS)
-  // unblock signals again
-  unblockUserSignals();
-#endif
-
-  RELEASE_SM_LOCK;
-
-  //PAR_TICKY_TP();
-}
-
-
-/* -----------------------------------------------------------------------------
-   Weak Pointers
-
-   traverse_weak_ptr_list is called possibly many times during garbage
-   collection.  It returns a flag indicating whether it did any work
-   (i.e. called evacuate on any live pointers).
-
-   Invariant: traverse_weak_ptr_list is called when the heap is in an
-   idempotent state.  That means that there are no pending
-   evacuate/scavenge operations.  This invariant helps the weak
-   pointer code decide which weak pointers are dead - if there are no
-   new live weak pointers, then all the currently unreachable ones are
-   dead.
-
-   For generational GC: we just don't try to finalize weak pointers in
-   older generations than the one we're collecting.  This could
-   probably be optimised by keeping per-generation lists of weak
-   pointers, but for a few weak pointers this scheme will work.
-
-   There are three distinct stages to processing weak pointers:
-
-   - weak_stage == WeakPtrs
-
-     We process all the weak pointers whos keys are alive (evacuate
-     their values and finalizers), and repeat until we can find no new
-     live keys.  If no live keys are found in this pass, then we
-     evacuate the finalizers of all the dead weak pointers in order to
-     run them.
-
-   - weak_stage == WeakThreads
-
-     Now, we discover which *threads* are still alive.  Pointers to
-     threads from the all_threads and main thread lists are the
-     weakest of all: a pointers from the finalizer of a dead weak
-     pointer can keep a thread alive.  Any threads found to be unreachable
-     are evacuated and placed on the resurrected_threads list so we 
-     can send them a signal later.
-
-   - weak_stage == WeakDone
-
-     No more evacuation is done.
-
-   -------------------------------------------------------------------------- */
-
-static rtsBool 
-traverse_weak_ptr_list(void)
-{
-  StgWeak *w, **last_w, *next_w;
-  StgClosure *new;
-  rtsBool flag = rtsFalse;
-
-  switch (weak_stage) {
-
-  case WeakDone:
-      return rtsFalse;
-
-  case WeakPtrs:
-      /* doesn't matter where we evacuate values/finalizers to, since
-       * these pointers are treated as roots (iff the keys are alive).
-       */
-      evac_gen = 0;
-      
-      last_w = &old_weak_ptr_list;
-      for (w = old_weak_ptr_list; w != NULL; w = next_w) {
-	  
-	  /* There might be a DEAD_WEAK on the list if finalizeWeak# was
-	   * called on a live weak pointer object.  Just remove it.
-	   */
-	  if (w->header.info == &stg_DEAD_WEAK_info) {
-	      next_w = ((StgDeadWeak *)w)->link;
-	      *last_w = next_w;
-	      continue;
-	  }
-	  
-	  switch (get_itbl(w)->type) {
-
-	  case EVACUATED:
-	      next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
-	      *last_w = next_w;
-	      continue;
-
-	  case WEAK:
-	      /* Now, check whether the key is reachable.
-	       */
-	      new = isAlive(w->key);
-	      if (new != NULL) {
-		  w->key = new;
-		  // evacuate the value and finalizer 
-		  w->value = evacuate(w->value);
-		  w->finalizer = evacuate(w->finalizer);
-		  // remove this weak ptr from the old_weak_ptr list 
-		  *last_w = w->link;
-		  // and put it on the new weak ptr list 
-		  next_w  = w->link;
-		  w->link = weak_ptr_list;
-		  weak_ptr_list = w;
-		  flag = rtsTrue;
-
-		  debugTrace(DEBUG_weak, 
-			     "weak pointer still alive at %p -> %p",
-			     w, w->key);
-		  continue;
-	      }
-	      else {
-		  last_w = &(w->link);
-		  next_w = w->link;
-		  continue;
-	      }
-
-	  default:
-	      barf("traverse_weak_ptr_list: not WEAK");
-	  }
-      }
-      
-      /* If we didn't make any changes, then we can go round and kill all
-       * the dead weak pointers.  The old_weak_ptr list is used as a list
-       * of pending finalizers later on.
-       */
-      if (flag == rtsFalse) {
-	  for (w = old_weak_ptr_list; w; w = w->link) {
-	      w->finalizer = evacuate(w->finalizer);
-	  }
-
-	  // Next, move to the WeakThreads stage after fully
-	  // scavenging the finalizers we've just evacuated.
-	  weak_stage = WeakThreads;
-      }
-
-      return rtsTrue;
-
-  case WeakThreads:
-      /* Now deal with the all_threads list, which behaves somewhat like
-       * the weak ptr list.  If we discover any threads that are about to
-       * become garbage, we wake them up and administer an exception.
-       */
-      {
-	  StgTSO *t, *tmp, *next, **prev;
-	  
-	  prev = &old_all_threads;
-	  for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
-	      
-	      tmp = (StgTSO *)isAlive((StgClosure *)t);
-	      
-	      if (tmp != NULL) {
-		  t = tmp;
-	      }
-	      
-	      ASSERT(get_itbl(t)->type == TSO);
-	      switch (t->what_next) {
-	      case ThreadRelocated:
-		  next = t->link;
-		  *prev = next;
-		  continue;
-	      case ThreadKilled:
-	      case ThreadComplete:
-		  // finshed or died.  The thread might still be alive, but we
-		  // don't keep it on the all_threads list.  Don't forget to
-		  // stub out its global_link field.
-		  next = t->global_link;
-		  t->global_link = END_TSO_QUEUE;
-		  *prev = next;
-		  continue;
-	      default:
-		  ;
-	      }
-	      
-	      if (tmp == NULL) {
-		  // not alive (yet): leave this thread on the
-		  // old_all_threads list.
-		  prev = &(t->global_link);
-		  next = t->global_link;
-	      } 
-	      else {
-		  // alive: move this thread onto the all_threads list.
-		  next = t->global_link;
-		  t->global_link = all_threads;
-		  all_threads  = t;
-		  *prev = next;
-	      }
-	  }
-      }
-      
-      /* If we evacuated any threads, we need to go back to the scavenger.
-       */
-      if (flag) return rtsTrue;
-
-      /* And resurrect any threads which were about to become garbage.
-       */
-      {
-	  StgTSO *t, *tmp, *next;
-	  for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
-	      next = t->global_link;
-	      tmp = (StgTSO *)evacuate((StgClosure *)t);
-	      tmp->global_link = resurrected_threads;
-	      resurrected_threads = tmp;
-	  }
-      }
-      
-      /* Finally, we can update the blackhole_queue.  This queue
-       * simply strings together TSOs blocked on black holes, it is
-       * not intended to keep anything alive.  Hence, we do not follow
-       * pointers on the blackhole_queue until now, when we have
-       * determined which TSOs are otherwise reachable.  We know at
-       * this point that all TSOs have been evacuated, however.
-       */
-      { 
-	  StgTSO **pt;
-	  for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
-	      *pt = (StgTSO *)isAlive((StgClosure *)*pt);
-	      ASSERT(*pt != NULL);
-	  }
-      }
-
-      weak_stage = WeakDone;  // *now* we're done,
-      return rtsTrue;         // but one more round of scavenging, please
-
-  default:
-      barf("traverse_weak_ptr_list");
-      return rtsTrue;
-  }
-
-}
-
-/* -----------------------------------------------------------------------------
-   The blackhole queue
-   
-   Threads on this list behave like weak pointers during the normal
-   phase of garbage collection: if the blackhole is reachable, then
-   the thread is reachable too.
-   -------------------------------------------------------------------------- */
-static rtsBool
-traverse_blackhole_queue (void)
-{
-    StgTSO *prev, *t, *tmp;
-    rtsBool flag;
-
-    flag = rtsFalse;
-    prev = NULL;
-
-    for (t = blackhole_queue; t != END_TSO_QUEUE; prev=t, t = t->link) {
-	if (! (tmp = (StgTSO *)isAlive((StgClosure*)t))) {
-	    if (isAlive(t->block_info.closure)) {
-		t = (StgTSO *)evacuate((StgClosure *)t);
-		if (prev) prev->link = t;
-		flag = rtsTrue;
-	    }
-	}
-    }
-    return flag;
-}
-
-/* -----------------------------------------------------------------------------
-   After GC, the live weak pointer list may have forwarding pointers
-   on it, because a weak pointer object was evacuated after being
-   moved to the live weak pointer list.  We remove those forwarding
-   pointers here.
-
-   Also, we don't consider weak pointer objects to be reachable, but
-   we must nevertheless consider them to be "live" and retain them.
-   Therefore any weak pointer objects which haven't as yet been
-   evacuated need to be evacuated now.
-   -------------------------------------------------------------------------- */
-
-
-static void
-mark_weak_ptr_list ( StgWeak **list )
-{
-  StgWeak *w, **last_w;
-
-  last_w = list;
-  for (w = *list; w; w = w->link) {
-      // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
-      ASSERT(w->header.info == &stg_DEAD_WEAK_info 
-	     || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
-      w = (StgWeak *)evacuate((StgClosure *)w);
-      *last_w = w;
-      last_w = &(w->link);
-  }
-}
-
-/* -----------------------------------------------------------------------------
-   isAlive determines whether the given closure is still alive (after
-   a garbage collection) or not.  It returns the new address of the
-   closure if it is alive, or NULL otherwise.
-
-   NOTE: Use it before compaction only!
-   -------------------------------------------------------------------------- */
-
-
-StgClosure *
-isAlive(StgClosure *p)
-{
-  const StgInfoTable *info;
-  bdescr *bd;
-
-  while (1) {
-
-    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-    info = get_itbl(p);
-
-    // ignore static closures 
-    //
-    // ToDo: for static closures, check the static link field.
-    // Problem here is that we sometimes don't set the link field, eg.
-    // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
-    //
-    if (!HEAP_ALLOCED(p)) {
-	return p;
-    }
-
-    // ignore closures in generations that we're not collecting. 
-    bd = Bdescr((P_)p);
-    if (bd->gen_no > N) {
-	return p;
-    }
-
-    // if it's a pointer into to-space, then we're done
-    if (bd->flags & BF_EVACUATED) {
-	return p;
-    }
-
-    // large objects use the evacuated flag
-    if (bd->flags & BF_LARGE) {
-	return NULL;
-    }
-
-    // check the mark bit for compacted steps
-    if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
-	return p;
-    }
-
-    switch (info->type) {
-
-    case IND:
-    case IND_STATIC:
-    case IND_PERM:
-    case IND_OLDGEN:		// rely on compatible layout with StgInd 
-    case IND_OLDGEN_PERM:
-      // follow indirections 
-      p = ((StgInd *)p)->indirectee;
-      continue;
-
-    case EVACUATED:
-      // alive! 
-      return ((StgEvacuated *)p)->evacuee;
-
-    case TSO:
-      if (((StgTSO *)p)->what_next == ThreadRelocated) {
-	p = (StgClosure *)((StgTSO *)p)->link;
-	continue;
-      } 
-      return NULL;
-
-    default:
-      // dead. 
-      return NULL;
-    }
-  }
-}
-
-static void
-mark_root(StgClosure **root)
-{
-  *root = evacuate(*root);
-}
-
-STATIC_INLINE void 
-upd_evacuee(StgClosure *p, StgClosure *dest)
-{
-    // not true: (ToDo: perhaps it should be)
-    // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
-    SET_INFO(p, &stg_EVACUATED_info);
-    ((StgEvacuated *)p)->evacuee = dest;
-}
-
-
-STATIC_INLINE StgClosure *
-copy(StgClosure *src, nat size, step *stp)
-{
-  StgPtr to, from;
-  nat i;
-#ifdef PROFILING
-  // @LDV profiling
-  nat size_org = size;
-#endif
-
-  TICK_GC_WORDS_COPIED(size);
-  /* Find out where we're going, using the handy "to" pointer in 
-   * the step of the source object.  If it turns out we need to
-   * evacuate to an older generation, adjust it here (see comment
-   * by evacuate()).
-   */
-  if (stp->gen_no < evac_gen) {
-      if (eager_promotion) {
-	  stp = &generations[evac_gen].steps[0];
-      } else {
-	  failed_to_evac = rtsTrue;
-      }
-  }
-
-  /* chain a new block onto the to-space for the destination step if
-   * necessary.
-   */
-  if (stp->hp + size >= stp->hpLim) {
-    gc_alloc_block(stp);
-  }
-
-  to = stp->hp;
-  from = (StgPtr)src;
-  stp->hp = to + size;
-  for (i = 0; i < size; i++) { // unroll for small i
-      to[i] = from[i];
-  }
-  upd_evacuee((StgClosure *)from,(StgClosure *)to);
-
-#ifdef PROFILING
-  // We store the size of the just evacuated object in the LDV word so that
-  // the profiler can guess the position of the next object later.
-  SET_EVACUAEE_FOR_LDV(from, size_org);
-#endif
-  return (StgClosure *)to;
-}
-
-// Same as copy() above, except the object will be allocated in memory
-// that will not be scavenged.  Used for object that have no pointer
-// fields.
-STATIC_INLINE StgClosure *
-copy_noscav(StgClosure *src, nat size, step *stp)
-{
-  StgPtr to, from;
-  nat i;
-#ifdef PROFILING
-  // @LDV profiling
-  nat size_org = size;
-#endif
-
-  TICK_GC_WORDS_COPIED(size);
-  /* Find out where we're going, using the handy "to" pointer in 
-   * the step of the source object.  If it turns out we need to
-   * evacuate to an older generation, adjust it here (see comment
-   * by evacuate()).
-   */
-  if (stp->gen_no < evac_gen) {
-      if (eager_promotion) {
-	  stp = &generations[evac_gen].steps[0];
-      } else {
-	  failed_to_evac = rtsTrue;
-      }
-  }
-
-  /* chain a new block onto the to-space for the destination step if
-   * necessary.
-   */
-  if (stp->scavd_hp + size >= stp->scavd_hpLim) {
-    gc_alloc_scavd_block(stp);
-  }
-
-  to = stp->scavd_hp;
-  from = (StgPtr)src;
-  stp->scavd_hp = to + size;
-  for (i = 0; i < size; i++) { // unroll for small i
-      to[i] = from[i];
-  }
-  upd_evacuee((StgClosure *)from,(StgClosure *)to);
-
-#ifdef PROFILING
-  // We store the size of the just evacuated object in the LDV word so that
-  // the profiler can guess the position of the next object later.
-  SET_EVACUAEE_FOR_LDV(from, size_org);
-#endif
-  return (StgClosure *)to;
-}
-
-/* Special version of copy() for when we only want to copy the info
- * pointer of an object, but reserve some padding after it.  This is
- * used to optimise evacuation of BLACKHOLEs.
- */
-
-
-static StgClosure *
-copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
-{
-  P_ dest, to, from;
-#ifdef PROFILING
-  // @LDV profiling
-  nat size_to_copy_org = size_to_copy;
-#endif
-
-  TICK_GC_WORDS_COPIED(size_to_copy);
-  if (stp->gen_no < evac_gen) {
-      if (eager_promotion) {
-	  stp = &generations[evac_gen].steps[0];
-      } else {
-	  failed_to_evac = rtsTrue;
-      }
-  }
-
-  if (stp->hp + size_to_reserve >= stp->hpLim) {
-    gc_alloc_block(stp);
-  }
-
-  for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
-    *to++ = *from++;
-  }
-  
-  dest = stp->hp;
-  stp->hp += size_to_reserve;
-  upd_evacuee(src,(StgClosure *)dest);
-#ifdef PROFILING
-  // We store the size of the just evacuated object in the LDV word so that
-  // the profiler can guess the position of the next object later.
-  // size_to_copy_org is wrong because the closure already occupies size_to_reserve
-  // words.
-  SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
-  // fill the slop
-  if (size_to_reserve - size_to_copy_org > 0)
-    LDV_FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org)); 
-#endif
-  return (StgClosure *)dest;
-}
-
-
-/* -----------------------------------------------------------------------------
-   Evacuate a large object
-
-   This just consists of removing the object from the (doubly-linked)
-   step->large_objects list, and linking it on to the (singly-linked)
-   step->new_large_objects list, from where it will be scavenged later.
-
-   Convention: bd->flags has BF_EVACUATED set for a large object
-   that has been evacuated, or unset otherwise.
-   -------------------------------------------------------------------------- */
-
-
-STATIC_INLINE void
-evacuate_large(StgPtr p)
-{
-  bdescr *bd = Bdescr(p);
-  step *stp;
-
-  // object must be at the beginning of the block (or be a ByteArray)
-  ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
-	 (((W_)p & BLOCK_MASK) == 0));
-
-  // already evacuated? 
-  if (bd->flags & BF_EVACUATED) { 
-    /* Don't forget to set the failed_to_evac flag if we didn't get
-     * the desired destination (see comments in evacuate()).
-     */
-    if (bd->gen_no < evac_gen) {
-      failed_to_evac = rtsTrue;
-      TICK_GC_FAILED_PROMOTION();
-    }
-    return;
-  }
-
-  stp = bd->step;
-  // remove from large_object list 
-  if (bd->u.back) {
-    bd->u.back->link = bd->link;
-  } else { // first object in the list 
-    stp->large_objects = bd->link;
-  }
-  if (bd->link) {
-    bd->link->u.back = bd->u.back;
-  }
-  
-  /* link it on to the evacuated large object list of the destination step
-   */
-  stp = bd->step->to;
-  if (stp->gen_no < evac_gen) {
-      if (eager_promotion) {
-	  stp = &generations[evac_gen].steps[0];
-      } else {
-	  failed_to_evac = rtsTrue;
-      }
-  }
-
-  bd->step = stp;
-  bd->gen_no = stp->gen_no;
-  bd->link = stp->new_large_objects;
-  stp->new_large_objects = bd;
-  bd->flags |= BF_EVACUATED;
-}
-
-/* -----------------------------------------------------------------------------
-   Evacuate
-
-   This is called (eventually) for every live object in the system.
-
-   The caller to evacuate specifies a desired generation in the
-   evac_gen global variable.  The following conditions apply to
-   evacuating an object which resides in generation M when we're
-   collecting up to generation N
-
-   if  M >= evac_gen 
-           if  M > N     do nothing
-	   else          evac to step->to
-
-   if  M < evac_gen      evac to evac_gen, step 0
-
-   if the object is already evacuated, then we check which generation
-   it now resides in.
-
-   if  M >= evac_gen     do nothing
-   if  M <  evac_gen     set failed_to_evac flag to indicate that we
-                         didn't manage to evacuate this object into evac_gen.
-
-
-   OPTIMISATION NOTES:
-
-   evacuate() is the single most important function performance-wise
-   in the GC.  Various things have been tried to speed it up, but as
-   far as I can tell the code generated by gcc 3.2 with -O2 is about
-   as good as it's going to get.  We pass the argument to evacuate()
-   in a register using the 'regparm' attribute (see the prototype for
-   evacuate() near the top of this file).
-
-   Changing evacuate() to take an (StgClosure **) rather than
-   returning the new pointer seems attractive, because we can avoid
-   writing back the pointer when it hasn't changed (eg. for a static
-   object, or an object in a generation > N).  However, I tried it and
-   it doesn't help.  One reason is that the (StgClosure **) pointer
-   gets spilled to the stack inside evacuate(), resulting in far more
-   extra reads/writes than we save.
-   -------------------------------------------------------------------------- */
-
-REGPARM1 static StgClosure *
-evacuate(StgClosure *q)
-{
-#if defined(PAR)
-  StgClosure *to;
-#endif
-  bdescr *bd = NULL;
-  step *stp;
-  const StgInfoTable *info;
-
-loop:
-  ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
-
-  if (!HEAP_ALLOCED(q)) {
-
-      if (!major_gc) return q;
-
-      info = get_itbl(q);
-      switch (info->type) {
-
-      case THUNK_STATIC:
-	  if (info->srt_bitmap != 0 && 
-	      *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
-	      *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
-	      static_objects = (StgClosure *)q;
-	  }
-	  return q;
-	  
-      case FUN_STATIC:
-	  if (info->srt_bitmap != 0 && 
-	      *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
-	      *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
-	      static_objects = (StgClosure *)q;
-	  }
-	  return q;
-	  
-      case IND_STATIC:
-	  /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
-	   * on the CAF list, so don't do anything with it here (we'll
-	   * scavenge it later).
-	   */
-	  if (((StgIndStatic *)q)->saved_info == NULL
-	      && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
-	      *IND_STATIC_LINK((StgClosure *)q) = static_objects;
-	      static_objects = (StgClosure *)q;
-	  }
-	  return q;
-	  
-      case CONSTR_STATIC:
-	  if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
-	      *STATIC_LINK(info,(StgClosure *)q) = static_objects;
-	      static_objects = (StgClosure *)q;
-	  }
-	  return q;
-	  
-      case CONSTR_NOCAF_STATIC:
-	  /* no need to put these on the static linked list, they don't need
-	   * to be scavenged.
-	   */
-	  return q;
-	  
-      default:
-	  barf("evacuate(static): strange closure type %d", (int)(info->type));
-      }
-  }
-
-  bd = Bdescr((P_)q);
-
-  if (bd->gen_no > N) {
-      /* Can't evacuate this object, because it's in a generation
-       * older than the ones we're collecting.  Let's hope that it's
-       * in evac_gen or older, or we will have to arrange to track
-       * this pointer using the mutable list.
-       */
-      if (bd->gen_no < evac_gen) {
-	  // nope 
-	  failed_to_evac = rtsTrue;
-	  TICK_GC_FAILED_PROMOTION();
-      }
-      return q;
-  }
-
-  if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
-
-      /* pointer into to-space: just return it.  This normally
-       * shouldn't happen, but alllowing it makes certain things
-       * slightly easier (eg. the mutable list can contain the same
-       * object twice, for example).
-       */
-      if (bd->flags & BF_EVACUATED) {
-	  if (bd->gen_no < evac_gen) {
-	      failed_to_evac = rtsTrue;
-	      TICK_GC_FAILED_PROMOTION();
-	  }
-	  return q;
-      }
-
-      /* evacuate large objects by re-linking them onto a different list.
-       */
-      if (bd->flags & BF_LARGE) {
-	  info = get_itbl(q);
-	  if (info->type == TSO && 
-	      ((StgTSO *)q)->what_next == ThreadRelocated) {
-	      q = (StgClosure *)((StgTSO *)q)->link;
-	      goto loop;
-	  }
-	  evacuate_large((P_)q);
-	  return q;
-      }
-      
-      /* If the object is in a step that we're compacting, then we
-       * need to use an alternative evacuate procedure.
-       */
-      if (bd->flags & BF_COMPACTED) {
-	  if (!is_marked((P_)q,bd)) {
-	      mark((P_)q,bd);
-	      if (mark_stack_full()) {
-		  mark_stack_overflowed = rtsTrue;
-		  reset_mark_stack();
-	      }
-	      push_mark_stack((P_)q);
-	  }
-	  return q;
-      }
-  }
-      
-  stp = bd->step->to;
-
-  info = get_itbl(q);
-  
-  switch (info->type) {
-
-  case MUT_VAR_CLEAN:
-  case MUT_VAR_DIRTY:
-  case MVAR:
-      return copy(q,sizeW_fromITBL(info),stp);
-
-  case CONSTR_0_1:
-  { 
-      StgWord w = (StgWord)q->payload[0];
-      if (q->header.info == Czh_con_info &&
-	  // unsigned, so always true:  (StgChar)w >= MIN_CHARLIKE &&  
-	  (StgChar)w <= MAX_CHARLIKE) {
-	  return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
-      }
-      if (q->header.info == Izh_con_info &&
-	  (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
-	  return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
-      }
-      // else
-      return copy_noscav(q,sizeofW(StgHeader)+1,stp);
-  }
-
-  case FUN_0_1:
-  case FUN_1_0:
-  case CONSTR_1_0:
-    return copy(q,sizeofW(StgHeader)+1,stp);
-
-  case THUNK_1_0:
-  case THUNK_0_1:
-    return copy(q,sizeofW(StgThunk)+1,stp);
-
-  case THUNK_1_1:
-  case THUNK_2_0:
-  case THUNK_0_2:
-#ifdef NO_PROMOTE_THUNKS
-    if (bd->gen_no == 0 && 
-	bd->step->no != 0 &&
-	bd->step->no == generations[bd->gen_no].n_steps-1) {
-      stp = bd->step;
-    }
-#endif
-    return copy(q,sizeofW(StgThunk)+2,stp);
-
-  case FUN_1_1:
-  case FUN_2_0:
-  case CONSTR_1_1:
-  case CONSTR_2_0:
-  case FUN_0_2:
-    return copy(q,sizeofW(StgHeader)+2,stp);
-
-  case CONSTR_0_2:
-    return copy_noscav(q,sizeofW(StgHeader)+2,stp);
-
-  case THUNK:
-    return copy(q,thunk_sizeW_fromITBL(info),stp);
-
-  case FUN:
-  case CONSTR:
-  case IND_PERM:
-  case IND_OLDGEN_PERM:
-  case WEAK:
-  case STABLE_NAME:
-    return copy(q,sizeW_fromITBL(info),stp);
-
-  case BCO:
-      return copy(q,bco_sizeW((StgBCO *)q),stp);
-
-  case CAF_BLACKHOLE:
-  case SE_CAF_BLACKHOLE:
-  case SE_BLACKHOLE:
-  case BLACKHOLE:
-    return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
-
-  case THUNK_SELECTOR:
-    {
-	StgClosure *p;
-	const StgInfoTable *info_ptr;
-
-	if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
-	    return copy(q,THUNK_SELECTOR_sizeW(),stp);
-	}
-
-	// stashed away for LDV profiling, see below
-	info_ptr = q->header.info;
-
-	p = eval_thunk_selector(info->layout.selector_offset,
-				(StgSelector *)q);
-
-	if (p == NULL) {
-	    return copy(q,THUNK_SELECTOR_sizeW(),stp);
-	} else {
-	    StgClosure *val;
-	    // q is still BLACKHOLE'd.
-	    thunk_selector_depth++;
-	    val = evacuate(p);
-	    thunk_selector_depth--;
-
-#ifdef PROFILING
-	    // For the purposes of LDV profiling, we have destroyed
-	    // the original selector thunk.
-	    SET_INFO(q, info_ptr);
-	    LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(q);
-#endif
-
-	    // Update the THUNK_SELECTOR with an indirection to the
-	    // EVACUATED closure now at p.  Why do this rather than
-	    // upd_evacuee(q,p)?  Because we have an invariant that an
-	    // EVACUATED closure always points to an object in the
-	    // same or an older generation (required by the short-cut
-	    // test in the EVACUATED case, below).
-	    SET_INFO(q, &stg_IND_info);
-	    ((StgInd *)q)->indirectee = p;
-
-	    // For the purposes of LDV profiling, we have created an
-	    // indirection.
-	    LDV_RECORD_CREATE(q);
-
-	    return val;
-	}
-    }
-
-  case IND:
-  case IND_OLDGEN:
-    // follow chains of indirections, don't evacuate them 
-    q = ((StgInd*)q)->indirectee;
-    goto loop;
-
-  case RET_BCO:
-  case RET_SMALL:
-  case RET_VEC_SMALL:
-  case RET_BIG:
-  case RET_VEC_BIG:
-  case RET_DYN:
-  case UPDATE_FRAME:
-  case STOP_FRAME:
-  case CATCH_FRAME:
-  case CATCH_STM_FRAME:
-  case CATCH_RETRY_FRAME:
-  case ATOMICALLY_FRAME:
-    // shouldn't see these 
-    barf("evacuate: stack frame at %p\n", q);
-
-  case PAP:
-      return copy(q,pap_sizeW((StgPAP*)q),stp);
-
-  case AP:
-      return copy(q,ap_sizeW((StgAP*)q),stp);
-
-  case AP_STACK:
-      return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
-
-  case EVACUATED:
-    /* Already evacuated, just return the forwarding address.
-     * HOWEVER: if the requested destination generation (evac_gen) is
-     * older than the actual generation (because the object was
-     * already evacuated to a younger generation) then we have to
-     * set the failed_to_evac flag to indicate that we couldn't 
-     * manage to promote the object to the desired generation.
-     */
-    /* 
-     * Optimisation: the check is fairly expensive, but we can often
-     * shortcut it if either the required generation is 0, or the
-     * current object (the EVACUATED) is in a high enough generation.
-     * We know that an EVACUATED always points to an object in the
-     * same or an older generation.  stp is the lowest step that the
-     * current object would be evacuated to, so we only do the full
-     * check if stp is too low.
-     */
-    if (evac_gen > 0 && stp->gen_no < evac_gen) {  // optimisation 
-      StgClosure *p = ((StgEvacuated*)q)->evacuee;
-      if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
-	failed_to_evac = rtsTrue;
-	TICK_GC_FAILED_PROMOTION();
-      }
-    }
-    return ((StgEvacuated*)q)->evacuee;
-
-  case ARR_WORDS:
-      // just copy the block 
-      return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
-
-  case MUT_ARR_PTRS_CLEAN:
-  case MUT_ARR_PTRS_DIRTY:
-  case MUT_ARR_PTRS_FROZEN:
-  case MUT_ARR_PTRS_FROZEN0:
-      // just copy the block 
-      return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
-
-  case TSO:
-    {
-      StgTSO *tso = (StgTSO *)q;
-
-      /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
-       */
-      if (tso->what_next == ThreadRelocated) {
-	q = (StgClosure *)tso->link;
-	goto loop;
-      }
-
-      /* To evacuate a small TSO, we need to relocate the update frame
-       * list it contains.  
-       */
-      {
-	  StgTSO *new_tso;
-	  StgPtr p, q;
-
-	  new_tso = (StgTSO *)copyPart((StgClosure *)tso,
-				       tso_sizeW(tso),
-				       sizeofW(StgTSO), stp);
-	  move_TSO(tso, new_tso);
-	  for (p = tso->sp, q = new_tso->sp;
-	       p < tso->stack+tso->stack_size;) {
-	      *q++ = *p++;
-	  }
-	  
-	  return (StgClosure *)new_tso;
-      }
-    }
-
-#if defined(PAR)
-  case RBH:
-    {
-      //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
-      to = copy(q,BLACKHOLE_sizeW(),stp); 
-      //ToDo: derive size etc from reverted IP
-      //to = copy(q,size,stp);
-      debugTrace(DEBUG_gc, "evacuate: RBH %p (%s) to %p (%s)",
-		 q, info_type(q), to, info_type(to));
-      return to;
-    }
-  
-  case BLOCKED_FETCH:
-    ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOD_SIZE);
-    to = copy(q,sizeofW(StgBlockedFetch),stp);
-    debugTrace(DEBUG_gc, "evacuate: %p (%s) to %p (%s)",
-	       q, info_type(q), to, info_type(to));
-    return to;
-
-# ifdef DIST    
-  case REMOTE_REF:
-# endif
-  case FETCH_ME:
-    ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
-    to = copy(q,sizeofW(StgFetchMe),stp);
-    debugTrace(DEBUG_gc, "evacuate: %p (%s) to %p (%s)",
-	       q, info_type(q), to, info_type(to)));
-    return to;
-
-  case FETCH_ME_BQ:
-    ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
-    to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
-    debugTrace(DEBUG_gc, "evacuate: %p (%s) to %p (%s)",
-	       q, info_type(q), to, info_type(to)));
-    return to;
-#endif
-
-  case TREC_HEADER: 
-    return copy(q,sizeofW(StgTRecHeader),stp);
-
-  case TVAR_WATCH_QUEUE:
-    return copy(q,sizeofW(StgTVarWatchQueue),stp);
-
-  case TVAR:
-    return copy(q,sizeofW(StgTVar),stp);
-    
-  case TREC_CHUNK:
-    return copy(q,sizeofW(StgTRecChunk),stp);
-
-  case ATOMIC_INVARIANT:
-    return copy(q,sizeofW(StgAtomicInvariant),stp);
-
-  case INVARIANT_CHECK_QUEUE:
-    return copy(q,sizeofW(StgInvariantCheckQueue),stp);
-
-  default:
-    barf("evacuate: strange closure type %d", (int)(info->type));
-  }
-
-  barf("evacuate");
-}
-
-/* -----------------------------------------------------------------------------
-   Evaluate a THUNK_SELECTOR if possible.
-
-   returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
-   a closure pointer if we evaluated it and this is the result.  Note
-   that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
-   reducing it to HNF, just that we have eliminated the selection.
-   The result might be another thunk, or even another THUNK_SELECTOR.
-
-   If the return value is non-NULL, the original selector thunk has
-   been BLACKHOLE'd, and should be updated with an indirection or a
-   forwarding pointer.  If the return value is NULL, then the selector
-   thunk is unchanged.
-
-   ***
-   ToDo: the treatment of THUNK_SELECTORS could be improved in the
-   following way (from a suggestion by Ian Lynagh):
-
-   We can have a chain like this:
-
-      sel_0 --> (a,b)
-                 |
-                 |-----> sel_0 --> (a,b)
-                                    |
-                                    |-----> sel_0 --> ...
-
-   and the depth limit means we don't go all the way to the end of the
-   chain, which results in a space leak.  This affects the recursive
-   call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
-   the recursive call to eval_thunk_selector() in
-   eval_thunk_selector().
-
-   We could eliminate the depth bound in this case, in the following
-   way:
-
-      - traverse the chain once to discover the *value* of the 
-        THUNK_SELECTOR.  Mark all THUNK_SELECTORS that we
-        visit on the way as having been visited already (somehow).
-
-      - in a second pass, traverse the chain again updating all
-        THUNK_SEELCTORS that we find on the way with indirections to
-        the value.
-
-      - if we encounter a "marked" THUNK_SELECTOR in a normal 
-        evacuate(), we konw it can't be updated so just evac it.
-
-   Program that illustrates the problem:
-
-	foo [] = ([], [])
-	foo (x:xs) = let (ys, zs) = foo xs
-	             in if x >= 0 then (x:ys, zs) else (ys, x:zs)
-
-	main = bar [1..(100000000::Int)]
-	bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
-
-   -------------------------------------------------------------------------- */
-
-static inline rtsBool
-is_to_space ( StgClosure *p )
-{
-    bdescr *bd;
-
-    bd = Bdescr((StgPtr)p);
-    if (HEAP_ALLOCED(p) &&
-	((bd->flags & BF_EVACUATED) 
-	 || ((bd->flags & BF_COMPACTED) &&
-	     is_marked((P_)p,bd)))) {
-	return rtsTrue;
-    } else {
-	return rtsFalse;
-    }
-}    
-
-static StgClosure *
-eval_thunk_selector( nat field, StgSelector * p )
-{
-    StgInfoTable *info;
-    const StgInfoTable *info_ptr;
-    StgClosure *selectee;
-    
-    selectee = p->selectee;
-
-    // Save the real info pointer (NOTE: not the same as get_itbl()).
-    info_ptr = p->header.info;
-
-    // If the THUNK_SELECTOR is in a generation that we are not
-    // collecting, then bail out early.  We won't be able to save any
-    // space in any case, and updating with an indirection is trickier
-    // in an old gen.
-    if (Bdescr((StgPtr)p)->gen_no > N) {
-	return NULL;
-    }
-
-    // BLACKHOLE the selector thunk, since it is now under evaluation.
-    // This is important to stop us going into an infinite loop if
-    // this selector thunk eventually refers to itself.
-    SET_INFO(p,&stg_BLACKHOLE_info);
-
-selector_loop:
-
-    // We don't want to end up in to-space, because this causes
-    // problems when the GC later tries to evacuate the result of
-    // eval_thunk_selector().  There are various ways this could
-    // happen:
-    //
-    // 1. following an IND_STATIC
-    //
-    // 2. when the old generation is compacted, the mark phase updates
-    //    from-space pointers to be to-space pointers, and we can't
-    //    reliably tell which we're following (eg. from an IND_STATIC).
-    // 
-    // 3. compacting GC again: if we're looking at a constructor in
-    //    the compacted generation, it might point directly to objects
-    //    in to-space.  We must bale out here, otherwise doing the selection
-    //    will result in a to-space pointer being returned.
-    //
-    //  (1) is dealt with using a BF_EVACUATED test on the
-    //  selectee. (2) and (3): we can tell if we're looking at an
-    //  object in the compacted generation that might point to
-    //  to-space objects by testing that (a) it is BF_COMPACTED, (b)
-    //  the compacted generation is being collected, and (c) the
-    //  object is marked.  Only a marked object may have pointers that
-    //  point to to-space objects, because that happens when
-    //  scavenging.
-    //
-    //  The to-space test is now embodied in the in_to_space() inline
-    //  function, as it is re-used below.
-    //
-    if (is_to_space(selectee)) {
-	goto bale_out;
-    }
-
-    info = get_itbl(selectee);
-    switch (info->type) {
-      case CONSTR:
-      case CONSTR_1_0:
-      case CONSTR_0_1:
-      case CONSTR_2_0:
-      case CONSTR_1_1:
-      case CONSTR_0_2:
-      case CONSTR_STATIC:
-      case CONSTR_NOCAF_STATIC:
-	  // check that the size is in range 
-	  ASSERT(field <  (StgWord32)(info->layout.payload.ptrs + 
-				      info->layout.payload.nptrs));
-	  
-	  // Select the right field from the constructor, and check
-	  // that the result isn't in to-space.  It might be in
-	  // to-space if, for example, this constructor contains
-	  // pointers to younger-gen objects (and is on the mut-once
-	  // list).
-	  //
-	  { 
-	      StgClosure *q;
-	      q = selectee->payload[field];
-	      if (is_to_space(q)) {
-		  goto bale_out;
-	      } else {
-		  return q;
-	      }
-	  }
-
-      case IND:
-      case IND_PERM:
-      case IND_OLDGEN:
-      case IND_OLDGEN_PERM:
-      case IND_STATIC:
-	  selectee = ((StgInd *)selectee)->indirectee;
-	  goto selector_loop;
-
-      case EVACUATED:
-	  // We don't follow pointers into to-space; the constructor
-	  // has already been evacuated, so we won't save any space
-	  // leaks by evaluating this selector thunk anyhow.
-	  break;
-
-      case THUNK_SELECTOR:
-      {
-	  StgClosure *val;
-
-	  // check that we don't recurse too much, re-using the
-	  // depth bound also used in evacuate().
-	  if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
-	      break;
-	  }
-	  thunk_selector_depth++;
-
-	  val = eval_thunk_selector(info->layout.selector_offset, 
-				    (StgSelector *)selectee);
-
-	  thunk_selector_depth--;
-
-	  if (val == NULL) { 
-	      break;
-	  } else {
-	      // We evaluated this selector thunk, so update it with
-	      // an indirection.  NOTE: we don't use UPD_IND here,
-	      // because we are guaranteed that p is in a generation
-	      // that we are collecting, and we never want to put the
-	      // indirection on a mutable list.
-#ifdef PROFILING
-	      // For the purposes of LDV profiling, we have destroyed
-	      // the original selector thunk.
-	      SET_INFO(p, info_ptr);
-	      LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
-#endif
-	      ((StgInd *)selectee)->indirectee = val;
-	      SET_INFO(selectee,&stg_IND_info);
-
-	      // For the purposes of LDV profiling, we have created an
-	      // indirection.
-	      LDV_RECORD_CREATE(selectee);
-
-	      selectee = val;
-	      goto selector_loop;
-	  }
-      }
-
-      case AP:
-      case AP_STACK:
-      case THUNK:
-      case THUNK_1_0:
-      case THUNK_0_1:
-      case THUNK_2_0:
-      case THUNK_1_1:
-      case THUNK_0_2:
-      case THUNK_STATIC:
-      case CAF_BLACKHOLE:
-      case SE_CAF_BLACKHOLE:
-      case SE_BLACKHOLE:
-      case BLACKHOLE:
-#if defined(PAR)
-      case RBH:
-      case BLOCKED_FETCH:
-# ifdef DIST    
-      case REMOTE_REF:
-# endif
-      case FETCH_ME:
-      case FETCH_ME_BQ:
-#endif
-	  // not evaluated yet 
-	  break;
-    
-      default:
-	barf("eval_thunk_selector: strange selectee %d",
-	     (int)(info->type));
-    }
-
-bale_out:
-    // We didn't manage to evaluate this thunk; restore the old info pointer
-    SET_INFO(p, info_ptr);
-    return NULL;
-}
-
-/* -----------------------------------------------------------------------------
-   move_TSO is called to update the TSO structure after it has been
-   moved from one place to another.
-   -------------------------------------------------------------------------- */
-
-void
-move_TSO (StgTSO *src, StgTSO *dest)
-{
-    ptrdiff_t diff;
-
-    // relocate the stack pointer... 
-    diff = (StgPtr)dest - (StgPtr)src; // In *words* 
-    dest->sp = (StgPtr)dest->sp + diff;
-}
-
-/* Similar to scavenge_large_bitmap(), but we don't write back the
- * pointers we get back from evacuate().
- */
-static void
-scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
-{
-    nat i, b, size;
-    StgWord bitmap;
-    StgClosure **p;
-    
-    b = 0;
-    bitmap = large_srt->l.bitmap[b];
-    size   = (nat)large_srt->l.size;
-    p      = (StgClosure **)large_srt->srt;
-    for (i = 0; i < size; ) {
-	if ((bitmap & 1) != 0) {
-	    evacuate(*p);
-	}
-	i++;
-	p++;
-	if (i % BITS_IN(W_) == 0) {
-	    b++;
-	    bitmap = large_srt->l.bitmap[b];
-	} else {
-	    bitmap = bitmap >> 1;
-	}
-    }
-}
-
-/* evacuate the SRT.  If srt_bitmap is zero, then there isn't an
- * srt field in the info table.  That's ok, because we'll
- * never dereference it.
- */
-STATIC_INLINE void
-scavenge_srt (StgClosure **srt, nat srt_bitmap)
-{
-  nat bitmap;
-  StgClosure **p;
-
-  bitmap = srt_bitmap;
-  p = srt;
-
-  if (bitmap == (StgHalfWord)(-1)) {  
-      scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
-      return;
-  }
-
-  while (bitmap != 0) {
-      if ((bitmap & 1) != 0) {
-#ifdef ENABLE_WIN32_DLL_SUPPORT
-	  // Special-case to handle references to closures hiding out in DLLs, since
-	  // double indirections required to get at those. The code generator knows
-	  // which is which when generating the SRT, so it stores the (indirect)
-	  // reference to the DLL closure in the table by first adding one to it.
-	  // We check for this here, and undo the addition before evacuating it.
-	  // 
-	  // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
-	  // closure that's fixed at link-time, and no extra magic is required.
-	  if ( (unsigned long)(*srt) & 0x1 ) {
-	      evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
-	  } else {
-	      evacuate(*p);
-	  }
-#else
-	  evacuate(*p);
-#endif
-      }
-      p++;
-      bitmap = bitmap >> 1;
-  }
-}
-
-
-STATIC_INLINE void
-scavenge_thunk_srt(const StgInfoTable *info)
-{
-    StgThunkInfoTable *thunk_info;
-
-    if (!major_gc) return;
-
-    thunk_info = itbl_to_thunk_itbl(info);
-    scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
-}
-
-STATIC_INLINE void
-scavenge_fun_srt(const StgInfoTable *info)
-{
-    StgFunInfoTable *fun_info;
-
-    if (!major_gc) return;
-  
-    fun_info = itbl_to_fun_itbl(info);
-    scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
-}
-
-/* -----------------------------------------------------------------------------
-   Scavenge a TSO.
-   -------------------------------------------------------------------------- */
-
-static void
-scavengeTSO (StgTSO *tso)
-{
-    if (   tso->why_blocked == BlockedOnMVar
-	|| tso->why_blocked == BlockedOnBlackHole
-	|| tso->why_blocked == BlockedOnException
-#if defined(PAR)
-	|| tso->why_blocked == BlockedOnGA
-	|| tso->why_blocked == BlockedOnGA_NoSend
-#endif
-	) {
-	tso->block_info.closure = evacuate(tso->block_info.closure);
-    }
-    tso->blocked_exceptions = 
-	(StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
-    
-    // We don't always chase the link field: TSOs on the blackhole
-    // queue are not automatically alive, so the link field is a
-    // "weak" pointer in that case.
-    if (tso->why_blocked != BlockedOnBlackHole) {
-	tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
-    }
-
-    // scavange current transaction record
-    tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
-    
-    // scavenge this thread's stack 
-    scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
-}
-
-/* -----------------------------------------------------------------------------
-   Blocks of function args occur on the stack (at the top) and
-   in PAPs.
-   -------------------------------------------------------------------------- */
-
-STATIC_INLINE StgPtr
-scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
-{
-    StgPtr p;
-    StgWord bitmap;
-    nat size;
-
-    p = (StgPtr)args;
-    switch (fun_info->f.fun_type) {
-    case ARG_GEN:
-	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
-	size = BITMAP_SIZE(fun_info->f.b.bitmap);
-	goto small_bitmap;
-    case ARG_GEN_BIG:
-	size = GET_FUN_LARGE_BITMAP(fun_info)->size;
-	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
-	p += size;
-	break;
-    default:
-	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
-	size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
-    small_bitmap:
-	while (size > 0) {
-	    if ((bitmap & 1) == 0) {
-		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	    }
-	    p++;
-	    bitmap = bitmap >> 1;
-	    size--;
-	}
-	break;
-    }
-    return p;
-}
-
-STATIC_INLINE StgPtr
-scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
-{
-    StgPtr p;
-    StgWord bitmap;
-    StgFunInfoTable *fun_info;
-    
-    fun_info = get_fun_itbl(fun);
-    ASSERT(fun_info->i.type != PAP);
-    p = (StgPtr)payload;
-
-    switch (fun_info->f.fun_type) {
-    case ARG_GEN:
-	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
-	goto small_bitmap;
-    case ARG_GEN_BIG:
-	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
-	p += size;
-	break;
-    case ARG_BCO:
-	scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
-	p += size;
-	break;
-    default:
-	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
-    small_bitmap:
-	while (size > 0) {
-	    if ((bitmap & 1) == 0) {
-		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	    }
-	    p++;
-	    bitmap = bitmap >> 1;
-	    size--;
-	}
-	break;
-    }
-    return p;
-}
-
-STATIC_INLINE StgPtr
-scavenge_PAP (StgPAP *pap)
-{
-    pap->fun = evacuate(pap->fun);
-    return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
-}
-
-STATIC_INLINE StgPtr
-scavenge_AP (StgAP *ap)
-{
-    ap->fun = evacuate(ap->fun);
-    return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
-}
-
-/* -----------------------------------------------------------------------------
-   Scavenge a given step until there are no more objects in this step
-   to scavenge.
-
-   evac_gen is set by the caller to be either zero (for a step in a
-   generation < N) or G where G is the generation of the step being
-   scavenged.  
-
-   We sometimes temporarily change evac_gen back to zero if we're
-   scavenging a mutable object where early promotion isn't such a good
-   idea.  
-   -------------------------------------------------------------------------- */
-
-static void
-scavenge(step *stp)
-{
-  StgPtr p, q;
-  StgInfoTable *info;
-  bdescr *bd;
-  nat saved_evac_gen = evac_gen;
-
-  p = stp->scan;
-  bd = stp->scan_bd;
-
-  failed_to_evac = rtsFalse;
-
-  /* scavenge phase - standard breadth-first scavenging of the
-   * evacuated objects 
-   */
-
-  while (bd != stp->hp_bd || p < stp->hp) {
-
-    // If we're at the end of this block, move on to the next block 
-    if (bd != stp->hp_bd && p == bd->free) {
-      bd = bd->link;
-      p = bd->start;
-      continue;
-    }
-
-    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-    info = get_itbl((StgClosure *)p);
-    
-    ASSERT(thunk_selector_depth == 0);
-
-    q = p;
-    switch (info->type) {
-
-    case MVAR:
-    { 
-	StgMVar *mvar = ((StgMVar *)p);
-	evac_gen = 0;
-	mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
-	mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
-	mvar->value = evacuate((StgClosure *)mvar->value);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable.
-	p += sizeofW(StgMVar);
-	break;
-    }
-
-    case FUN_2_0:
-	scavenge_fun_srt(info);
-	((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
-	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2;
-	break;
-
-    case THUNK_2_0:
-	scavenge_thunk_srt(info);
-	((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
-	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
-	p += sizeofW(StgThunk) + 2;
-	break;
-
-    case CONSTR_2_0:
-	((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
-	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2;
-	break;
-	
-    case THUNK_1_0:
-	scavenge_thunk_srt(info);
-	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
-	p += sizeofW(StgThunk) + 1;
-	break;
-	
-    case FUN_1_0:
-	scavenge_fun_srt(info);
-    case CONSTR_1_0:
-	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 1;
-	break;
-	
-    case THUNK_0_1:
-	scavenge_thunk_srt(info);
-	p += sizeofW(StgThunk) + 1;
-	break;
-	
-    case FUN_0_1:
-	scavenge_fun_srt(info);
-    case CONSTR_0_1:
-	p += sizeofW(StgHeader) + 1;
-	break;
-	
-    case THUNK_0_2:
-	scavenge_thunk_srt(info);
-	p += sizeofW(StgThunk) + 2;
-	break;
-	
-    case FUN_0_2:
-	scavenge_fun_srt(info);
-    case CONSTR_0_2:
-	p += sizeofW(StgHeader) + 2;
-	break;
-	
-    case THUNK_1_1:
-	scavenge_thunk_srt(info);
-	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
-	p += sizeofW(StgThunk) + 2;
-	break;
-
-    case FUN_1_1:
-	scavenge_fun_srt(info);
-    case CONSTR_1_1:
-	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2;
-	break;
-	
-    case FUN:
-	scavenge_fun_srt(info);
-	goto gen_obj;
-
-    case THUNK:
-    {
-	StgPtr end;
-
-	scavenge_thunk_srt(info);
-	end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
-	for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-	p += info->layout.payload.nptrs;
-	break;
-    }
-	
-    gen_obj:
-    case CONSTR:
-    case WEAK:
-    case STABLE_NAME:
-    {
-	StgPtr end;
-
-	end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
-	for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-	p += info->layout.payload.nptrs;
-	break;
-    }
-
-    case BCO: {
-	StgBCO *bco = (StgBCO *)p;
-	bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
-	bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
-	bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
-	bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
-	p += bco_sizeW(bco);
-	break;
-    }
-
-    case IND_PERM:
-      if (stp->gen->no != 0) {
-#ifdef PROFILING
-        // @LDV profiling
-        // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an 
-        // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
-        LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
-#endif        
-        // 
-        // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
-        //
-	SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
-
-        // We pretend that p has just been created.
-        LDV_RECORD_CREATE((StgClosure *)p);
-      }
-	// fall through 
-    case IND_OLDGEN_PERM:
-	((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
-	p += sizeofW(StgInd);
-	break;
-
-    case MUT_VAR_CLEAN:
-    case MUT_VAR_DIRTY: {
-	rtsBool saved_eager_promotion = eager_promotion;
-
-	eager_promotion = rtsFalse;
-	((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
-	eager_promotion = saved_eager_promotion;
-
-	if (failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
-	}
-	p += sizeofW(StgMutVar);
-	break;
-    }
-
-    case CAF_BLACKHOLE:
-    case SE_CAF_BLACKHOLE:
-    case SE_BLACKHOLE:
-    case BLACKHOLE:
-	p += BLACKHOLE_sizeW();
-	break;
-
-    case THUNK_SELECTOR:
-    { 
-	StgSelector *s = (StgSelector *)p;
-	s->selectee = evacuate(s->selectee);
-	p += THUNK_SELECTOR_sizeW();
-	break;
-    }
-
-    // A chunk of stack saved in a heap object
-    case AP_STACK:
-    {
-	StgAP_STACK *ap = (StgAP_STACK *)p;
-
-	ap->fun = evacuate(ap->fun);
-	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
-	p = (StgPtr)ap->payload + ap->size;
-	break;
-    }
-
-    case PAP:
-	p = scavenge_PAP((StgPAP *)p);
-	break;
-
-    case AP:
-	p = scavenge_AP((StgAP *)p);
-	break;
-
-    case ARR_WORDS:
-	// nothing to follow 
-	p += arr_words_sizeW((StgArrWords *)p);
-	break;
-
-    case MUT_ARR_PTRS_CLEAN:
-    case MUT_ARR_PTRS_DIRTY:
-	// follow everything 
-    {
-	StgPtr next;
-	rtsBool saved_eager;
-
-	// We don't eagerly promote objects pointed to by a mutable
-	// array, but if we find the array only points to objects in
-	// the same or an older generation, we mark it "clean" and
-	// avoid traversing it during minor GCs.
-	saved_eager = eager_promotion;
-	eager_promotion = rtsFalse;
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-	eager_promotion = saved_eager;
-
-	if (failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
-	}
-
-	failed_to_evac = rtsTrue; // always put it on the mutable list.
-	break;
-    }
-
-    case MUT_ARR_PTRS_FROZEN:
-    case MUT_ARR_PTRS_FROZEN0:
-	// follow everything 
-    {
-	StgPtr next;
-
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-
-	// If we're going to put this object on the mutable list, then
-	// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
-	if (failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
-	}
-	break;
-    }
-
-    case TSO:
-    { 
-	StgTSO *tso = (StgTSO *)p;
-	rtsBool saved_eager = eager_promotion;
-
-	eager_promotion = rtsFalse;
-	scavengeTSO(tso);
-	eager_promotion = saved_eager;
-
-	if (failed_to_evac) {
-	    tso->flags |= TSO_DIRTY;
-	} else {
-	    tso->flags &= ~TSO_DIRTY;
-	}
-
-	failed_to_evac = rtsTrue; // always on the mutable list
-	p += tso_sizeW(tso);
-	break;
-    }
-
-#if defined(PAR)
-    case RBH:
-    { 
-#if 0
-	nat size, ptrs, nonptrs, vhs;
-	char str[80];
-	StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
-#endif
-	StgRBH *rbh = (StgRBH *)p;
-	(StgClosure *)rbh->blocking_queue = 
-	    evacuate((StgClosure *)rbh->blocking_queue);
-	failed_to_evac = rtsTrue;  // mutable anyhow.
-	debugTrace(DEBUG_gc, "scavenge: RBH %p (%s) (new blocking_queue link=%p)",
-		   p, info_type(p), (StgClosure *)rbh->blocking_queue);
-	// ToDo: use size of reverted closure here!
-	p += BLACKHOLE_sizeW(); 
-	break;
-    }
-
-    case BLOCKED_FETCH:
-    { 
-	StgBlockedFetch *bf = (StgBlockedFetch *)p;
-	// follow the pointer to the node which is being demanded 
-	(StgClosure *)bf->node = 
-	    evacuate((StgClosure *)bf->node);
-	// follow the link to the rest of the blocking queue 
-	(StgClosure *)bf->link = 
-	    evacuate((StgClosure *)bf->link);
-	debugTrace(DEBUG_gc, "scavenge: %p (%s); node is now %p; exciting, isn't it",
-		   bf, info_type((StgClosure *)bf), 
-		   bf->node, info_type(bf->node)));
-	p += sizeofW(StgBlockedFetch);
-	break;
-    }
-
-#ifdef DIST
-    case REMOTE_REF:
-#endif
-    case FETCH_ME:
-	p += sizeofW(StgFetchMe);
-	break; // nothing to do in this case
-
-    case FETCH_ME_BQ:
-    { 
-	StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
-	(StgClosure *)fmbq->blocking_queue = 
-	    evacuate((StgClosure *)fmbq->blocking_queue);
-	debugTrace(DEBUG_gc, "scavenge: %p (%s) exciting, isn't it",
-		   p, info_type((StgClosure *)p)));
-	p += sizeofW(StgFetchMeBlockingQueue);
-	break;
-    }
-#endif
-
-    case TVAR_WATCH_QUEUE:
-      {
-	StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	evac_gen = 0;
-	wq->closure = (StgClosure*)evacuate((StgClosure*)wq->closure);
-	wq->next_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->next_queue_entry);
-	wq->prev_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTVarWatchQueue);
-	break;
-      }
-
-    case TVAR:
-      {
-	StgTVar *tvar = ((StgTVar *) p);
-	evac_gen = 0;
-	tvar->current_value = evacuate((StgClosure*)tvar->current_value);
-	tvar->first_watch_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)tvar->first_watch_queue_entry);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTVar);
-	break;
-      }
-
-    case TREC_HEADER:
-      {
-        StgTRecHeader *trec = ((StgTRecHeader *) p);
-        evac_gen = 0;
-	trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
-	trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
-	trec->invariants_to_check = (StgInvariantCheckQueue *)evacuate((StgClosure*)trec->invariants_to_check);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTRecHeader);
-        break;
-      }
-
-    case TREC_CHUNK:
-      {
-	StgWord i;
-	StgTRecChunk *tc = ((StgTRecChunk *) p);
-	TRecEntry *e = &(tc -> entries[0]);
-	evac_gen = 0;
-	tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
-	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
-	  e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
-	  e->expected_value = evacuate((StgClosure*)e->expected_value);
-	  e->new_value = evacuate((StgClosure*)e->new_value);
-	}
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTRecChunk);
-	break;
-      }
-
-    case ATOMIC_INVARIANT:
-      {
-        StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-        evac_gen = 0;
-	invariant->code = (StgClosure *)evacuate(invariant->code);
-	invariant->last_execution = (StgTRecHeader *)evacuate((StgClosure*)invariant->last_execution);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgAtomicInvariant);
-        break;
-      }
-
-    case INVARIANT_CHECK_QUEUE:
-      {
-        StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-        evac_gen = 0;
-	queue->invariant = (StgAtomicInvariant *)evacuate((StgClosure*)queue->invariant);
-	queue->my_execution = (StgTRecHeader *)evacuate((StgClosure*)queue->my_execution);
-	queue->next_queue_entry = (StgInvariantCheckQueue *)evacuate((StgClosure*)queue->next_queue_entry);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgInvariantCheckQueue);
-        break;
-      }
-
-    default:
-	barf("scavenge: unimplemented/strange closure type %d @ %p", 
-	     info->type, p);
-    }
-
-    /*
-     * We need to record the current object on the mutable list if
-     *  (a) It is actually mutable, or 
-     *  (b) It contains pointers to a younger generation.
-     * Case (b) arises if we didn't manage to promote everything that
-     * the current object points to into the current generation.
-     */
-    if (failed_to_evac) {
-	failed_to_evac = rtsFalse;
-	if (stp->gen_no > 0) {
-	    recordMutableGen((StgClosure *)q, stp->gen);
-	}
-    }
-  }
-
-  stp->scan_bd = bd;
-  stp->scan = p;
-}    
-
-/* -----------------------------------------------------------------------------
-   Scavenge everything on the mark stack.
-
-   This is slightly different from scavenge():
-      - we don't walk linearly through the objects, so the scavenger
-        doesn't need to advance the pointer on to the next object.
-   -------------------------------------------------------------------------- */
-
-static void
-scavenge_mark_stack(void)
-{
-    StgPtr p, q;
-    StgInfoTable *info;
-    nat saved_evac_gen;
-
-    evac_gen = oldest_gen->no;
-    saved_evac_gen = evac_gen;
-
-linear_scan:
-    while (!mark_stack_empty()) {
-	p = pop_mark_stack();
-
-	ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-	info = get_itbl((StgClosure *)p);
-	
-	q = p;
-	switch (info->type) {
-	    
-	case MVAR:
-	{
-	    StgMVar *mvar = ((StgMVar *)p);
-	    evac_gen = 0;
-	    mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
-	    mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
-	    mvar->value = evacuate((StgClosure *)mvar->value);
-	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsTrue; // mutable.
-	    break;
-	}
-
-	case FUN_2_0:
-	    scavenge_fun_srt(info);
-	    ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
-	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	    break;
-
-	case THUNK_2_0:
-	    scavenge_thunk_srt(info);
-	    ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
-	    ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
-	    break;
-
-	case CONSTR_2_0:
-	    ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
-	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	    break;
-	
-	case FUN_1_0:
-	case FUN_1_1:
-	    scavenge_fun_srt(info);
-	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	    break;
-
-	case THUNK_1_0:
-	case THUNK_1_1:
-	    scavenge_thunk_srt(info);
-	    ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
-	    break;
-
-	case CONSTR_1_0:
-	case CONSTR_1_1:
-	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
-	    break;
-	
-	case FUN_0_1:
-	case FUN_0_2:
-	    scavenge_fun_srt(info);
-	    break;
-
-	case THUNK_0_1:
-	case THUNK_0_2:
-	    scavenge_thunk_srt(info);
-	    break;
-
-	case CONSTR_0_1:
-	case CONSTR_0_2:
-	    break;
-	
-	case FUN:
-	    scavenge_fun_srt(info);
-	    goto gen_obj;
-
-	case THUNK:
-	{
-	    StgPtr end;
-	    
-	    scavenge_thunk_srt(info);
-	    end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
-	    for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
-		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	    }
-	    break;
-	}
-	
-	gen_obj:
-	case CONSTR:
-	case WEAK:
-	case STABLE_NAME:
-	{
-	    StgPtr end;
-	    
-	    end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
-	    for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
-		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	    }
-	    break;
-	}
-
-	case BCO: {
-	    StgBCO *bco = (StgBCO *)p;
-	    bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
-	    bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
-	    bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
-	    bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
-	    break;
-	}
-
-	case IND_PERM:
-	    // don't need to do anything here: the only possible case
-	    // is that we're in a 1-space compacting collector, with
-	    // no "old" generation.
-	    break;
-
-	case IND_OLDGEN:
-	case IND_OLDGEN_PERM:
-	    ((StgInd *)p)->indirectee = 
-		evacuate(((StgInd *)p)->indirectee);
-	    break;
-
-	case MUT_VAR_CLEAN:
-	case MUT_VAR_DIRTY: {
-	    rtsBool saved_eager_promotion = eager_promotion;
-	    
-	    eager_promotion = rtsFalse;
-	    ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
-	    eager_promotion = saved_eager_promotion;
-	    
-	    if (failed_to_evac) {
-		((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
-	    } else {
-		((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
-	    }
-	    break;
-	}
-
-	case CAF_BLACKHOLE:
-	case SE_CAF_BLACKHOLE:
-	case SE_BLACKHOLE:
-	case BLACKHOLE:
-	case ARR_WORDS:
-	    break;
-
-	case THUNK_SELECTOR:
-	{ 
-	    StgSelector *s = (StgSelector *)p;
-	    s->selectee = evacuate(s->selectee);
-	    break;
-	}
-
-	// A chunk of stack saved in a heap object
-	case AP_STACK:
-	{
-	    StgAP_STACK *ap = (StgAP_STACK *)p;
-	    
-	    ap->fun = evacuate(ap->fun);
-	    scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
-	    break;
-	}
-
-	case PAP:
-	    scavenge_PAP((StgPAP *)p);
-	    break;
-
-	case AP:
-	    scavenge_AP((StgAP *)p);
-	    break;
-      
-	case MUT_ARR_PTRS_CLEAN:
-	case MUT_ARR_PTRS_DIRTY:
-	    // follow everything 
-	{
-	    StgPtr next;
-	    rtsBool saved_eager;
-
-	    // We don't eagerly promote objects pointed to by a mutable
-	    // array, but if we find the array only points to objects in
-	    // the same or an older generation, we mark it "clean" and
-	    // avoid traversing it during minor GCs.
-	    saved_eager = eager_promotion;
-	    eager_promotion = rtsFalse;
-	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	    }
-	    eager_promotion = saved_eager;
-
-	    if (failed_to_evac) {
-		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
-	    } else {
-		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
-	    }
-
-	    failed_to_evac = rtsTrue; // mutable anyhow.
-	    break;
-	}
-
-	case MUT_ARR_PTRS_FROZEN:
-	case MUT_ARR_PTRS_FROZEN0:
-	    // follow everything 
-	{
-	    StgPtr next, q = p;
-	    
-	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	    }
-
-	    // If we're going to put this object on the mutable list, then
-	    // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
-	    if (failed_to_evac) {
-		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
-	    } else {
-		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
-	    }
-	    break;
-	}
-
-	case TSO:
-	{ 
-	    StgTSO *tso = (StgTSO *)p;
-	    rtsBool saved_eager = eager_promotion;
-
-	    eager_promotion = rtsFalse;
-	    scavengeTSO(tso);
-	    eager_promotion = saved_eager;
-	    
-	    if (failed_to_evac) {
-		tso->flags |= TSO_DIRTY;
-	    } else {
-		tso->flags &= ~TSO_DIRTY;
-	    }
-	    
-	    failed_to_evac = rtsTrue; // always on the mutable list
-	    break;
-	}
-
-#if defined(PAR)
-	case RBH:
-	{ 
-#if 0
-	    nat size, ptrs, nonptrs, vhs;
-	    char str[80];
-	    StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
-#endif
-	    StgRBH *rbh = (StgRBH *)p;
-	    bh->blocking_queue = 
-		(StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
-	    failed_to_evac = rtsTrue;  // mutable anyhow.
-	    debugTrace(DEBUG_gc, "scavenge: RBH %p (%s) (new blocking_queue link=%p)",
-		       p, info_type(p), (StgClosure *)rbh->blocking_queue));
-	    break;
-	}
-	
-	case BLOCKED_FETCH:
-	{ 
-	    StgBlockedFetch *bf = (StgBlockedFetch *)p;
-	    // follow the pointer to the node which is being demanded 
-	    (StgClosure *)bf->node = 
-		evacuate((StgClosure *)bf->node);
-	    // follow the link to the rest of the blocking queue 
-	    (StgClosure *)bf->link = 
-		evacuate((StgClosure *)bf->link);
-	    debugTrace(DEBUG_gc, "scavenge: %p (%s); node is now %p; exciting, isn't it",
-		       bf, info_type((StgClosure *)bf), 
-		       bf->node, info_type(bf->node)));
-	    break;
-	}
-
-#ifdef DIST
-	case REMOTE_REF:
-#endif
-	case FETCH_ME:
-	    break; // nothing to do in this case
-
-	case FETCH_ME_BQ:
-	{ 
-	    StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
-	    (StgClosure *)fmbq->blocking_queue = 
-		evacuate((StgClosure *)fmbq->blocking_queue);
-	    debugTrace(DEBUG_gc, "scavenge: %p (%s) exciting, isn't it",
-		       p, info_type((StgClosure *)p)));
-	    break;
-	}
-#endif /* PAR */
-
-	case TVAR_WATCH_QUEUE:
-	  {
-	    StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	    evac_gen = 0;
-            wq->closure = (StgClosure*)evacuate((StgClosure*)wq->closure);
-	    wq->next_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->next_queue_entry);
-	    wq->prev_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
-	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsTrue; // mutable
-	    break;
-	  }
-	  
-	case TVAR:
-	  {
-	    StgTVar *tvar = ((StgTVar *) p);
-	    evac_gen = 0;
-	    tvar->current_value = evacuate((StgClosure*)tvar->current_value);
-	    tvar->first_watch_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)tvar->first_watch_queue_entry);
-	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsTrue; // mutable
-	    break;
-	  }
-	  
-	case TREC_CHUNK:
-	  {
-	    StgWord i;
-	    StgTRecChunk *tc = ((StgTRecChunk *) p);
-	    TRecEntry *e = &(tc -> entries[0]);
-	    evac_gen = 0;
-	    tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
-	    for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
-	      e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
-	      e->expected_value = evacuate((StgClosure*)e->expected_value);
-	      e->new_value = evacuate((StgClosure*)e->new_value);
-	    }
-	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsTrue; // mutable
-	    break;
-	  }
-
-	case TREC_HEADER:
-	  {
-	    StgTRecHeader *trec = ((StgTRecHeader *) p);
-	    evac_gen = 0;
-	    trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
-	    trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
-  	    trec->invariants_to_check = (StgInvariantCheckQueue *)evacuate((StgClosure*)trec->invariants_to_check);
-	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsTrue; // mutable
-	    break;
-	  }
-
-        case ATOMIC_INVARIANT:
-          {
-            StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-            evac_gen = 0;
-	    invariant->code = (StgClosure *)evacuate(invariant->code);
-    	    invariant->last_execution = (StgTRecHeader *)evacuate((StgClosure*)invariant->last_execution);
-	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsTrue; // mutable
-            break;
-          }
-
-        case INVARIANT_CHECK_QUEUE:
-          {
-            StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-            evac_gen = 0;
-    	    queue->invariant = (StgAtomicInvariant *)evacuate((StgClosure*)queue->invariant);
-	    queue->my_execution = (StgTRecHeader *)evacuate((StgClosure*)queue->my_execution);
-            queue->next_queue_entry = (StgInvariantCheckQueue *)evacuate((StgClosure*)queue->next_queue_entry);
-	    evac_gen = saved_evac_gen;
-	    failed_to_evac = rtsTrue; // mutable
-            break;
-          }
-
-	default:
-	    barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p", 
-		 info->type, p);
-	}
-
-	if (failed_to_evac) {
-	    failed_to_evac = rtsFalse;
-	    if (evac_gen > 0) {
-		recordMutableGen((StgClosure *)q, &generations[evac_gen]);
-	    }
-	}
-	
-	// mark the next bit to indicate "scavenged"
-	mark(q+1, Bdescr(q));
-
-    } // while (!mark_stack_empty())
-
-    // start a new linear scan if the mark stack overflowed at some point
-    if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
-	debugTrace(DEBUG_gc, "scavenge_mark_stack: starting linear scan");
-	mark_stack_overflowed = rtsFalse;
-	oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
-	oldgen_scan = oldgen_scan_bd->start;
-    }
-
-    if (oldgen_scan_bd) {
-	// push a new thing on the mark stack
-    loop:
-	// find a closure that is marked but not scavenged, and start
-	// from there.
-	while (oldgen_scan < oldgen_scan_bd->free 
-	       && !is_marked(oldgen_scan,oldgen_scan_bd)) {
-	    oldgen_scan++;
-	}
-
-	if (oldgen_scan < oldgen_scan_bd->free) {
-
-	    // already scavenged?
-	    if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
-		oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
-		goto loop;
-	    }
-	    push_mark_stack(oldgen_scan);
-	    // ToDo: bump the linear scan by the actual size of the object
-	    oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
-	    goto linear_scan;
-	}
-
-	oldgen_scan_bd = oldgen_scan_bd->link;
-	if (oldgen_scan_bd != NULL) {
-	    oldgen_scan = oldgen_scan_bd->start;
-	    goto loop;
-	}
-    }
-}
-
-/* -----------------------------------------------------------------------------
-   Scavenge one object.
-
-   This is used for objects that are temporarily marked as mutable
-   because they contain old-to-new generation pointers.  Only certain
-   objects can have this property.
-   -------------------------------------------------------------------------- */
-
-static rtsBool
-scavenge_one(StgPtr p)
-{
-    const StgInfoTable *info;
-    nat saved_evac_gen = evac_gen;
-    rtsBool no_luck;
-    
-    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-    info = get_itbl((StgClosure *)p);
-    
-    switch (info->type) {
-	
-    case MVAR:
-    { 
-	StgMVar *mvar = ((StgMVar *)p);
-	evac_gen = 0;
-	mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
-	mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
-	mvar->value = evacuate((StgClosure *)mvar->value);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable.
-	break;
-    }
-
-    case THUNK:
-    case THUNK_1_0:
-    case THUNK_0_1:
-    case THUNK_1_1:
-    case THUNK_0_2:
-    case THUNK_2_0:
-    {
-	StgPtr q, end;
-	
-	end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
-	for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
-	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
-	}
-	break;
-    }
-
-    case FUN:
-    case FUN_1_0:			// hardly worth specialising these guys
-    case FUN_0_1:
-    case FUN_1_1:
-    case FUN_0_2:
-    case FUN_2_0:
-    case CONSTR:
-    case CONSTR_1_0:
-    case CONSTR_0_1:
-    case CONSTR_1_1:
-    case CONSTR_0_2:
-    case CONSTR_2_0:
-    case WEAK:
-    case IND_PERM:
-    {
-	StgPtr q, end;
-	
-	end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
-	for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
-	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
-	}
-	break;
-    }
-    
-    case MUT_VAR_CLEAN:
-    case MUT_VAR_DIRTY: {
-	StgPtr q = p;
-	rtsBool saved_eager_promotion = eager_promotion;
-
-	eager_promotion = rtsFalse;
-	((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
-	eager_promotion = saved_eager_promotion;
-
-	if (failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
-	}
-	break;
-    }
-
-    case CAF_BLACKHOLE:
-    case SE_CAF_BLACKHOLE:
-    case SE_BLACKHOLE:
-    case BLACKHOLE:
-	break;
-	
-    case THUNK_SELECTOR:
-    { 
-	StgSelector *s = (StgSelector *)p;
-	s->selectee = evacuate(s->selectee);
-	break;
-    }
-    
-    case AP_STACK:
-    {
-	StgAP_STACK *ap = (StgAP_STACK *)p;
-
-	ap->fun = evacuate(ap->fun);
-	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
-	p = (StgPtr)ap->payload + ap->size;
-	break;
-    }
-
-    case PAP:
-	p = scavenge_PAP((StgPAP *)p);
-	break;
-
-    case AP:
-	p = scavenge_AP((StgAP *)p);
-	break;
-
-    case ARR_WORDS:
-	// nothing to follow 
-	break;
-
-    case MUT_ARR_PTRS_CLEAN:
-    case MUT_ARR_PTRS_DIRTY:
-    {
-	StgPtr next, q;
-	rtsBool saved_eager;
-
-	// We don't eagerly promote objects pointed to by a mutable
-	// array, but if we find the array only points to objects in
-	// the same or an older generation, we mark it "clean" and
-	// avoid traversing it during minor GCs.
-	saved_eager = eager_promotion;
-	eager_promotion = rtsFalse;
-	q = p;
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-	eager_promotion = saved_eager;
-
-	if (failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
-	}
-
-	failed_to_evac = rtsTrue;
-	break;
-    }
-
-    case MUT_ARR_PTRS_FROZEN:
-    case MUT_ARR_PTRS_FROZEN0:
-    {
-	// follow everything 
-	StgPtr next, q=p;
-      
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-
-	// If we're going to put this object on the mutable list, then
-	// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
-	if (failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
-	}
-	break;
-    }
-
-    case TSO:
-    {
-	StgTSO *tso = (StgTSO *)p;
-	rtsBool saved_eager = eager_promotion;
-
-	eager_promotion = rtsFalse;
-	scavengeTSO(tso);
-	eager_promotion = saved_eager;
-
-	if (failed_to_evac) {
-	    tso->flags |= TSO_DIRTY;
-	} else {
-	    tso->flags &= ~TSO_DIRTY;
-	}
-
-	failed_to_evac = rtsTrue; // always on the mutable list
-	break;
-    }
-  
-#if defined(PAR)
-    case RBH:
-    { 
-#if 0
-	nat size, ptrs, nonptrs, vhs;
-	char str[80];
-	StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
-#endif
-	StgRBH *rbh = (StgRBH *)p;
-	(StgClosure *)rbh->blocking_queue = 
-	    evacuate((StgClosure *)rbh->blocking_queue);
-	failed_to_evac = rtsTrue;  // mutable anyhow.
-	debugTrace(DEBUG_gc, "scavenge: RBH %p (%s) (new blocking_queue link=%p)",
-		   p, info_type(p), (StgClosure *)rbh->blocking_queue));
-	// ToDo: use size of reverted closure here!
-	break;
-    }
-
-    case BLOCKED_FETCH:
-    { 
-	StgBlockedFetch *bf = (StgBlockedFetch *)p;
-	// follow the pointer to the node which is being demanded 
-	(StgClosure *)bf->node = 
-	    evacuate((StgClosure *)bf->node);
-	// follow the link to the rest of the blocking queue 
-	(StgClosure *)bf->link = 
-	    evacuate((StgClosure *)bf->link);
-	debugTrace(DEBUG_gc,
-		   "scavenge: %p (%s); node is now %p; exciting, isn't it",
-		   bf, info_type((StgClosure *)bf), 
-		   bf->node, info_type(bf->node)));
-	break;
-    }
-
-#ifdef DIST
-    case REMOTE_REF:
-#endif
-    case FETCH_ME:
-	break; // nothing to do in this case
-
-    case FETCH_ME_BQ:
-    { 
-	StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
-	(StgClosure *)fmbq->blocking_queue = 
-	    evacuate((StgClosure *)fmbq->blocking_queue);
-	debugTrace(DEBUG_gc, "scavenge: %p (%s) exciting, isn't it",
-		   p, info_type((StgClosure *)p)));
-	break;
-    }
-#endif
-
-    case TVAR_WATCH_QUEUE:
-      {
-	StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	evac_gen = 0;
-        wq->closure = (StgClosure*)evacuate((StgClosure*)wq->closure);
-        wq->next_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->next_queue_entry);
-        wq->prev_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	break;
-      }
-
-    case TVAR:
-      {
-	StgTVar *tvar = ((StgTVar *) p);
-	evac_gen = 0;
-	tvar->current_value = evacuate((StgClosure*)tvar->current_value);
-        tvar->first_watch_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)tvar->first_watch_queue_entry);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	break;
-      }
-
-    case TREC_HEADER:
-      {
-        StgTRecHeader *trec = ((StgTRecHeader *) p);
-        evac_gen = 0;
-	trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
-	trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
-        trec->invariants_to_check = (StgInvariantCheckQueue *)evacuate((StgClosure*)trec->invariants_to_check);
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-        break;
-      }
-
-    case TREC_CHUNK:
-      {
-	StgWord i;
-	StgTRecChunk *tc = ((StgTRecChunk *) p);
-	TRecEntry *e = &(tc -> entries[0]);
-	evac_gen = 0;
-	tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
-	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
-	  e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
-	  e->expected_value = evacuate((StgClosure*)e->expected_value);
-	  e->new_value = evacuate((StgClosure*)e->new_value);
-	}
-	evac_gen = saved_evac_gen;
-	failed_to_evac = rtsTrue; // mutable
-	break;
-      }
-
-    case ATOMIC_INVARIANT:
-    {
-      StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-      evac_gen = 0;
-      invariant->code = (StgClosure *)evacuate(invariant->code);
-      invariant->last_execution = (StgTRecHeader *)evacuate((StgClosure*)invariant->last_execution);
-      evac_gen = saved_evac_gen;
-      failed_to_evac = rtsTrue; // mutable
-      break;
-    }
-
-    case INVARIANT_CHECK_QUEUE:
-    {
-      StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-      evac_gen = 0;
-      queue->invariant = (StgAtomicInvariant *)evacuate((StgClosure*)queue->invariant);
-      queue->my_execution = (StgTRecHeader *)evacuate((StgClosure*)queue->my_execution);
-      queue->next_queue_entry = (StgInvariantCheckQueue *)evacuate((StgClosure*)queue->next_queue_entry);
-      evac_gen = saved_evac_gen;
-      failed_to_evac = rtsTrue; // mutable
-      break;
-    }
-
-    case IND_OLDGEN:
-    case IND_OLDGEN_PERM:
-    case IND_STATIC:
-    {
-	/* Careful here: a THUNK can be on the mutable list because
-	 * it contains pointers to young gen objects.  If such a thunk
-	 * is updated, the IND_OLDGEN will be added to the mutable
-	 * list again, and we'll scavenge it twice.  evacuate()
-	 * doesn't check whether the object has already been
-	 * evacuated, so we perform that check here.
-	 */
-	StgClosure *q = ((StgInd *)p)->indirectee;
-	if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
-	    break;
-	}
-	((StgInd *)p)->indirectee = evacuate(q);
-    }
-
-#if 0 && defined(DEBUG)
-      if (RtsFlags.DebugFlags.gc) 
-      /* Debugging code to print out the size of the thing we just
-       * promoted 
-       */
-      { 
-	StgPtr start = gen->steps[0].scan;
-	bdescr *start_bd = gen->steps[0].scan_bd;
-	nat size = 0;
-	scavenge(&gen->steps[0]);
-	if (start_bd != gen->steps[0].scan_bd) {
-	  size += (P_)BLOCK_ROUND_UP(start) - start;
-	  start_bd = start_bd->link;
-	  while (start_bd != gen->steps[0].scan_bd) {
-	    size += BLOCK_SIZE_W;
-	    start_bd = start_bd->link;
-	  }
-	  size += gen->steps[0].scan -
-	    (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
-	} else {
-	  size = gen->steps[0].scan - start;
-	}
-	debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
-      }
-#endif
-      break;
-
-    default:
-	barf("scavenge_one: strange object %d", (int)(info->type));
-    }    
-
-    no_luck = failed_to_evac;
-    failed_to_evac = rtsFalse;
-    return (no_luck);
-}
-
-/* -----------------------------------------------------------------------------
-   Scavenging mutable lists.
-
-   We treat the mutable list of each generation > N (i.e. all the
-   generations older than the one being collected) as roots.  We also
-   remove non-mutable objects from the mutable list at this point.
-   -------------------------------------------------------------------------- */
-
-static void
-scavenge_mutable_list(generation *gen)
-{
-    bdescr *bd;
-    StgPtr p, q;
-
-    bd = gen->saved_mut_list;
-
-    evac_gen = gen->no;
-    for (; bd != NULL; bd = bd->link) {
-	for (q = bd->start; q < bd->free; q++) {
-	    p = (StgPtr)*q;
-	    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-
-#ifdef DEBUG	    
-	    switch (get_itbl((StgClosure *)p)->type) {
-	    case MUT_VAR_CLEAN:
-		barf("MUT_VAR_CLEAN on mutable list");
-	    case MUT_VAR_DIRTY:
-		mutlist_MUTVARS++; break;
-	    case MUT_ARR_PTRS_CLEAN:
-	    case MUT_ARR_PTRS_DIRTY:
-	    case MUT_ARR_PTRS_FROZEN:
-	    case MUT_ARR_PTRS_FROZEN0:
-		mutlist_MUTARRS++; break;
-	    default:
-		mutlist_OTHERS++; break;
-	    }
-#endif
-
-	    // Check whether this object is "clean", that is it
-	    // definitely doesn't point into a young generation.
-	    // Clean objects don't need to be scavenged.  Some clean
-	    // objects (MUT_VAR_CLEAN) are not kept on the mutable
-	    // list at all; others, such as MUT_ARR_PTRS_CLEAN and
-	    // TSO, are always on the mutable list.
-	    //
-	    switch (get_itbl((StgClosure *)p)->type) {
-	    case MUT_ARR_PTRS_CLEAN:
-		recordMutableGen((StgClosure *)p,gen);
-		continue;
-	    case TSO: {
-		StgTSO *tso = (StgTSO *)p;
-		if ((tso->flags & TSO_DIRTY) == 0) {
-		    // A clean TSO: we don't have to traverse its
-		    // stack.  However, we *do* follow the link field:
-		    // we don't want to have to mark a TSO dirty just
-		    // because we put it on a different queue.
-		    if (tso->why_blocked != BlockedOnBlackHole) {
-			tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
-		    }
-		    recordMutableGen((StgClosure *)p,gen);
-		    continue;
-		}
-	    }
-	    default:
-		;
-	    }
-
-	    if (scavenge_one(p)) {
-		// didn't manage to promote everything, so put the
-		// object back on the list.
-		recordMutableGen((StgClosure *)p,gen);
-	    }
-	}
-    }
-
-    // free the old mut_list
-    freeChain(gen->saved_mut_list);
-    gen->saved_mut_list = NULL;
-}
-
-
-static void
-scavenge_static(void)
-{
-  StgClosure* p = static_objects;
-  const StgInfoTable *info;
-
-  /* Always evacuate straight to the oldest generation for static
-   * objects */
-  evac_gen = oldest_gen->no;
-
-  /* keep going until we've scavenged all the objects on the linked
-     list... */
-  while (p != END_OF_STATIC_LIST) {
-
-    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-    info = get_itbl(p);
-    /*
-    if (info->type==RBH)
-      info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
-    */
-    // make sure the info pointer is into text space 
-    
-    /* Take this object *off* the static_objects list,
-     * and put it on the scavenged_static_objects list.
-     */
-    static_objects = *STATIC_LINK(info,p);
-    *STATIC_LINK(info,p) = scavenged_static_objects;
-    scavenged_static_objects = p;
-    
-    switch (info -> type) {
-      
-    case IND_STATIC:
-      {
-	StgInd *ind = (StgInd *)p;
-	ind->indirectee = evacuate(ind->indirectee);
-
-	/* might fail to evacuate it, in which case we have to pop it
-	 * back on the mutable list of the oldest generation.  We
-	 * leave it *on* the scavenged_static_objects list, though,
-	 * in case we visit this object again.
-	 */
-	if (failed_to_evac) {
-	  failed_to_evac = rtsFalse;
-	  recordMutableGen((StgClosure *)p,oldest_gen);
-	}
-	break;
-      }
-      
-    case THUNK_STATIC:
-      scavenge_thunk_srt(info);
-      break;
-
-    case FUN_STATIC:
-      scavenge_fun_srt(info);
-      break;
-      
-    case CONSTR_STATIC:
-      {	
-	StgPtr q, next;
-	
-	next = (P_)p->payload + info->layout.payload.ptrs;
-	// evacuate the pointers 
-	for (q = (P_)p->payload; q < next; q++) {
-	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
-	}
-	break;
-      }
-      
-    default:
-      barf("scavenge_static: strange closure %d", (int)(info->type));
-    }
-
-    ASSERT(failed_to_evac == rtsFalse);
-
-    /* get the next static object from the list.  Remember, there might
-     * be more stuff on this list now that we've done some evacuating!
-     * (static_objects is a global)
-     */
-    p = static_objects;
-  }
-}
-
-/* -----------------------------------------------------------------------------
-   scavenge a chunk of memory described by a bitmap
-   -------------------------------------------------------------------------- */
-
-static void
-scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
-{
-    nat i, b;
-    StgWord bitmap;
-    
-    b = 0;
-    bitmap = large_bitmap->bitmap[b];
-    for (i = 0; i < size; ) {
-	if ((bitmap & 1) == 0) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-	i++;
-	p++;
-	if (i % BITS_IN(W_) == 0) {
-	    b++;
-	    bitmap = large_bitmap->bitmap[b];
-	} else {
-	    bitmap = bitmap >> 1;
-	}
-    }
-}
-
-STATIC_INLINE StgPtr
-scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
-{
-    while (size > 0) {
-	if ((bitmap & 1) == 0) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	}
-	p++;
-	bitmap = bitmap >> 1;
-	size--;
-    }
-    return p;
-}
-
-/* -----------------------------------------------------------------------------
-   scavenge_stack walks over a section of stack and evacuates all the
-   objects pointed to by it.  We can use the same code for walking
-   AP_STACK_UPDs, since these are just sections of copied stack.
-   -------------------------------------------------------------------------- */
-
-
-static void
-scavenge_stack(StgPtr p, StgPtr stack_end)
-{
-  const StgRetInfoTable* info;
-  StgWord bitmap;
-  nat size;
-
-  /* 
-   * Each time around this loop, we are looking at a chunk of stack
-   * that starts with an activation record. 
-   */
-
-  while (p < stack_end) {
-    info  = get_ret_itbl((StgClosure *)p);
-      
-    switch (info->i.type) {
-	
-    case UPDATE_FRAME:
-	// In SMP, we can get update frames that point to indirections
-	// when two threads evaluate the same thunk.  We do attempt to
-	// discover this situation in threadPaused(), but it's
-	// possible that the following sequence occurs:
-	//
-	//        A             B
-	//                  enter T
-	//     enter T
-	//     blackhole T
-	//                  update T
-	//     GC
-	//
-	// Now T is an indirection, and the update frame is already
-	// marked on A's stack, so we won't traverse it again in
-	// threadPaused().  We could traverse the whole stack again
-	// before GC, but that seems like overkill.
-	//
-	// Scavenging this update frame as normal would be disastrous;
-	// the updatee would end up pointing to the value.  So we turn
-	// the indirection into an IND_PERM, so that evacuate will
-	// copy the indirection into the old generation instead of
-	// discarding it.
-	if (get_itbl(((StgUpdateFrame *)p)->updatee)->type == IND) {
-	    ((StgUpdateFrame *)p)->updatee->header.info = 
-		(StgInfoTable *)&stg_IND_PERM_info;
-	}
-	((StgUpdateFrame *)p)->updatee 
-	    = evacuate(((StgUpdateFrame *)p)->updatee);
-	p += sizeofW(StgUpdateFrame);
-	continue;
-
-      // small bitmap (< 32 entries, or 64 on a 64-bit machine) 
-    case CATCH_STM_FRAME:
-    case CATCH_RETRY_FRAME:
-    case ATOMICALLY_FRAME:
-    case STOP_FRAME:
-    case CATCH_FRAME:
-    case RET_SMALL:
-    case RET_VEC_SMALL:
-	bitmap = BITMAP_BITS(info->i.layout.bitmap);
-	size   = BITMAP_SIZE(info->i.layout.bitmap);
-	// NOTE: the payload starts immediately after the info-ptr, we
-	// don't have an StgHeader in the same sense as a heap closure.
-	p++;
-	p = scavenge_small_bitmap(p, size, bitmap);
-
-    follow_srt:
-	if (major_gc) 
-	    scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
-	continue;
-
-    case RET_BCO: {
-	StgBCO *bco;
-	nat size;
-
-	p++;
-	*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	bco = (StgBCO *)*p;
-	p++;
-	size = BCO_BITMAP_SIZE(bco);
-	scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
-	p += size;
-	continue;
-    }
-
-      // large bitmap (> 32 entries, or > 64 on a 64-bit machine) 
-    case RET_BIG:
-    case RET_VEC_BIG:
-    {
-	nat size;
-
-	size = GET_LARGE_BITMAP(&info->i)->size;
-	p++;
-	scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
-	p += size;
-	// and don't forget to follow the SRT 
-	goto follow_srt;
-    }
-
-      // Dynamic bitmap: the mask is stored on the stack, and
-      // there are a number of non-pointers followed by a number
-      // of pointers above the bitmapped area.  (see StgMacros.h,
-      // HEAP_CHK_GEN).
-    case RET_DYN:
-    {
-	StgWord dyn;
-	dyn = ((StgRetDyn *)p)->liveness;
-
-	// traverse the bitmap first
-	bitmap = RET_DYN_LIVENESS(dyn);
-	p      = (P_)&((StgRetDyn *)p)->payload[0];
-	size   = RET_DYN_BITMAP_SIZE;
-	p = scavenge_small_bitmap(p, size, bitmap);
-
-	// skip over the non-ptr words
-	p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
-	
-	// follow the ptr words
-	for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
-	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
-	    p++;
-	}
-	continue;
-    }
-
-    case RET_FUN:
-    {
-	StgRetFun *ret_fun = (StgRetFun *)p;
-	StgFunInfoTable *fun_info;
-
-	ret_fun->fun = evacuate(ret_fun->fun);
- 	fun_info = get_fun_itbl(ret_fun->fun);
-	p = scavenge_arg_block(fun_info, ret_fun->payload);
-	goto follow_srt;
-    }
-
-    default:
-	barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
-    }
-  }		     
-}
-
-/*-----------------------------------------------------------------------------
-  scavenge the large object list.
-
-  evac_gen set by caller; similar games played with evac_gen as with
-  scavenge() - see comment at the top of scavenge().  Most large
-  objects are (repeatedly) mutable, so most of the time evac_gen will
-  be zero.
-  --------------------------------------------------------------------------- */
-
-static void
-scavenge_large(step *stp)
-{
-  bdescr *bd;
-  StgPtr p;
-
-  bd = stp->new_large_objects;
-
-  for (; bd != NULL; bd = stp->new_large_objects) {
-
-    /* take this object *off* the large objects list and put it on
-     * the scavenged large objects list.  This is so that we can
-     * treat new_large_objects as a stack and push new objects on
-     * the front when evacuating.
-     */
-    stp->new_large_objects = bd->link;
-    dbl_link_onto(bd, &stp->scavenged_large_objects);
-
-    // update the block count in this step.
-    stp->n_scavenged_large_blocks += bd->blocks;
-
-    p = bd->start;
-    if (scavenge_one(p)) {
-	if (stp->gen_no > 0) {
-	    recordMutableGen((StgClosure *)p, stp->gen);
-	}
-    }
-  }
-}
-
-/* -----------------------------------------------------------------------------
-   Initialising the static object & mutable lists
-   -------------------------------------------------------------------------- */
-
-static void
-zero_static_object_list(StgClosure* first_static)
-{
-  StgClosure* p;
-  StgClosure* link;
-  const StgInfoTable *info;
-
-  for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
-    info = get_itbl(p);
-    link = *STATIC_LINK(info, p);
-    *STATIC_LINK(info,p) = NULL;
-  }
-}
-
-/* -----------------------------------------------------------------------------
-   Reverting CAFs
-   -------------------------------------------------------------------------- */
-
-void
-revertCAFs( void )
-{
-    StgIndStatic *c;
-
-    for (c = (StgIndStatic *)revertible_caf_list; c != NULL; 
-	 c = (StgIndStatic *)c->static_link) 
-    {
-	SET_INFO(c, c->saved_info);
-	c->saved_info = NULL;
-	// could, but not necessary: c->static_link = NULL; 
-    }
-    revertible_caf_list = NULL;
-}
-
-void
-markCAFs( evac_fn evac )
-{
-    StgIndStatic *c;
-
-    for (c = (StgIndStatic *)caf_list; c != NULL; 
-	 c = (StgIndStatic *)c->static_link) 
-    {
-	evac(&c->indirectee);
-    }
-    for (c = (StgIndStatic *)revertible_caf_list; c != NULL; 
-	 c = (StgIndStatic *)c->static_link) 
-    {
-	evac(&c->indirectee);
-    }
-}
-
-/* -----------------------------------------------------------------------------
-   Sanity code for CAF garbage collection.
-
-   With DEBUG turned on, we manage a CAF list in addition to the SRT
-   mechanism.  After GC, we run down the CAF list and blackhole any
-   CAFs which have been garbage collected.  This means we get an error
-   whenever the program tries to enter a garbage collected CAF.
-
-   Any garbage collected CAFs are taken off the CAF list at the same
-   time. 
-   -------------------------------------------------------------------------- */
-
-#if 0 && defined(DEBUG)
-
-static void
-gcCAFs(void)
-{
-  StgClosure*  p;
-  StgClosure** pp;
-  const StgInfoTable *info;
-  nat i;
-
-  i = 0;
-  p = caf_list;
-  pp = &caf_list;
-
-  while (p != NULL) {
-    
-    info = get_itbl(p);
-
-    ASSERT(info->type == IND_STATIC);
-
-    if (STATIC_LINK(info,p) == NULL) {
-	debugTrace(DEBUG_gccafs, "CAF gc'd at 0x%04lx", (long)p);
-	// black hole it 
-	SET_INFO(p,&stg_BLACKHOLE_info);
-	p = STATIC_LINK2(info,p);
-	*pp = p;
-    }
-    else {
-      pp = &STATIC_LINK2(info,p);
-      p = *pp;
-      i++;
-    }
-
-  }
-
-  debugTrace(DEBUG_gccafs, "%d CAFs live", i); 
-}
-#endif
-
-
-/* -----------------------------------------------------------------------------
- * Stack squeezing
- *
- * Code largely pinched from old RTS, then hacked to bits.  We also do
- * lazy black holing here.
- *
- * -------------------------------------------------------------------------- */
-
-struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
-
-static void
-stackSqueeze(StgTSO *tso, StgPtr bottom)
-{
-    StgPtr frame;
-    rtsBool prev_was_update_frame;
-    StgClosure *updatee = NULL;
-    StgRetInfoTable *info;
-    StgWord current_gap_size;
-    struct stack_gap *gap;
-
-    // Stage 1: 
-    //    Traverse the stack upwards, replacing adjacent update frames
-    //    with a single update frame and a "stack gap".  A stack gap
-    //    contains two values: the size of the gap, and the distance
-    //    to the next gap (or the stack top).
-
-    frame = tso->sp;
-
-    ASSERT(frame < bottom);
-    
-    prev_was_update_frame = rtsFalse;
-    current_gap_size = 0;
-    gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
-
-    while (frame < bottom) {
-	
-	info = get_ret_itbl((StgClosure *)frame);
-	switch (info->i.type) {
-
-	case UPDATE_FRAME:
-	{ 
-	    StgUpdateFrame *upd = (StgUpdateFrame *)frame;
-
-	    if (prev_was_update_frame) {
-
-		TICK_UPD_SQUEEZED();
-		/* wasn't there something about update squeezing and ticky to be
-		 * sorted out?  oh yes: we aren't counting each enter properly
-		 * in this case.  See the log somewhere.  KSW 1999-04-21
-		 *
-		 * Check two things: that the two update frames don't point to
-		 * the same object, and that the updatee_bypass isn't already an
-		 * indirection.  Both of these cases only happen when we're in a
-		 * block hole-style loop (and there are multiple update frames
-		 * on the stack pointing to the same closure), but they can both
-		 * screw us up if we don't check.
-		 */
-		if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
-		    UPD_IND_NOLOCK(upd->updatee, updatee);
-		}
-
-		// now mark this update frame as a stack gap.  The gap
-		// marker resides in the bottom-most update frame of
-		// the series of adjacent frames, and covers all the
-		// frames in this series.
-		current_gap_size += sizeofW(StgUpdateFrame);
-		((struct stack_gap *)frame)->gap_size = current_gap_size;
-		((struct stack_gap *)frame)->next_gap = gap;
-
-		frame += sizeofW(StgUpdateFrame);
-		continue;
-	    } 
-
-	    // single update frame, or the topmost update frame in a series
-	    else {
-		prev_was_update_frame = rtsTrue;
-		updatee = upd->updatee;
-		frame += sizeofW(StgUpdateFrame);
-		continue;
-	    }
-	}
-	    
-	default:
-	    prev_was_update_frame = rtsFalse;
-
-	    // we're not in a gap... check whether this is the end of a gap
-	    // (an update frame can't be the end of a gap).
-	    if (current_gap_size != 0) {
-		gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
-	    }
-	    current_gap_size = 0;
-
-	    frame += stack_frame_sizeW((StgClosure *)frame);
-	    continue;
-	}
-    }
-
-    if (current_gap_size != 0) {
-	gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
-    }
-
-    // Now we have a stack with gaps in it, and we have to walk down
-    // shoving the stack up to fill in the gaps.  A diagram might
-    // help:
-    //
-    //    +| ********* |
-    //     | ********* | <- sp
-    //     |           |
-    //     |           | <- gap_start
-    //     | ......... |                |
-    //     | stack_gap | <- gap         | chunk_size
-    //     | ......... |                | 
-    //     | ......... | <- gap_end     v
-    //     | ********* | 
-    //     | ********* | 
-    //     | ********* | 
-    //    -| ********* | 
-    //
-    // 'sp'  points the the current top-of-stack
-    // 'gap' points to the stack_gap structure inside the gap
-    // *****   indicates real stack data
-    // .....   indicates gap
-    // <empty> indicates unused
-    //
-    {
-	void *sp;
-	void *gap_start, *next_gap_start, *gap_end;
-	nat chunk_size;
-
-	next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
-	sp = next_gap_start;
-
-	while ((StgPtr)gap > tso->sp) {
-
-	    // we're working in *bytes* now...
-	    gap_start = next_gap_start;
-	    gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
-
-	    gap = gap->next_gap;
-	    next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
-
-	    chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
-	    sp -= chunk_size;
-	    memmove(sp, next_gap_start, chunk_size);
-	}
-
-	tso->sp = (StgPtr)sp;
-    }
-}    
-
-/* -----------------------------------------------------------------------------
- * Pausing a thread
- * 
- * We have to prepare for GC - this means doing lazy black holing
- * here.  We also take the opportunity to do stack squeezing if it's
- * turned on.
- * -------------------------------------------------------------------------- */
-void
-threadPaused(Capability *cap, StgTSO *tso)
-{
-    StgClosure *frame;
-    StgRetInfoTable *info;
-    StgClosure *bh;
-    StgPtr stack_end;
-    nat words_to_squeeze = 0;
-    nat weight           = 0;
-    nat weight_pending   = 0;
-    rtsBool prev_was_update_frame;
-    
-    // Check to see whether we have threads waiting to raise
-    // exceptions, and we're not blocking exceptions, or are blocked
-    // interruptibly.  This is important; if a thread is running with
-    // TSO_BLOCKEX and becomes blocked interruptibly, this is the only
-    // place we ensure that the blocked_exceptions get a chance.
-    maybePerformBlockedException (cap, tso);
-    if (tso->what_next == ThreadKilled) { return; }
-
-    stack_end = &tso->stack[tso->stack_size];
-    
-    frame = (StgClosure *)tso->sp;
-
-    while (1) {
-	// If we've already marked this frame, then stop here.
-	if (frame->header.info == (StgInfoTable *)&stg_marked_upd_frame_info) {
-	    goto end;
-	}
-
-	info = get_ret_itbl(frame);
-	
-	switch (info->i.type) {
-	    
-	case UPDATE_FRAME:
-
-	    SET_INFO(frame, (StgInfoTable *)&stg_marked_upd_frame_info);
-
-	    bh = ((StgUpdateFrame *)frame)->updatee;
-
-	    if (closure_IND(bh) || bh->header.info == &stg_BLACKHOLE_info) {
-		debugTrace(DEBUG_squeeze,
-			   "suspending duplicate work: %ld words of stack",
-			   (long)((StgPtr)frame - tso->sp));
-
-		// If this closure is already an indirection, then
-		// suspend the computation up to this point:
-		suspendComputation(cap,tso,(StgPtr)frame);
-
-		// Now drop the update frame, and arrange to return
-		// the value to the frame underneath:
-		tso->sp = (StgPtr)frame + sizeofW(StgUpdateFrame) - 2;
-		tso->sp[1] = (StgWord)bh;
-		tso->sp[0] = (W_)&stg_enter_info;
-
-		// And continue with threadPaused; there might be
-		// yet more computation to suspend.
-		threadPaused(cap,tso);
-		return;
-	    }
-
-	    if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
-#if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
-		debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh);
-#endif
-		// zero out the slop so that the sanity checker can tell
-		// where the next closure is.
-		DEBUG_FILL_SLOP(bh);
-#ifdef PROFILING
-		// @LDV profiling
-		// We pretend that bh is now dead.
-		LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
-#endif
-		SET_INFO(bh,&stg_BLACKHOLE_info);
-
-		// We pretend that bh has just been created.
-		LDV_RECORD_CREATE(bh);
-	    }
-	    
-	    frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
-	    if (prev_was_update_frame) {
-		words_to_squeeze += sizeofW(StgUpdateFrame);
-		weight += weight_pending;
-		weight_pending = 0;
-	    }
-	    prev_was_update_frame = rtsTrue;
-	    break;
-	    
-	case STOP_FRAME:
-	    goto end;
-	    
-	    // normal stack frames; do nothing except advance the pointer
-	default:
-	{
-	    nat frame_size = stack_frame_sizeW(frame);
-	    weight_pending += frame_size;
-	    frame = (StgClosure *)((StgPtr)frame + frame_size);
-	    prev_was_update_frame = rtsFalse;
-	}
-	}
-    }
-
-end:
-    debugTrace(DEBUG_squeeze, 
-	       "words_to_squeeze: %d, weight: %d, squeeze: %s", 
-	       words_to_squeeze, weight, 
-	       weight < words_to_squeeze ? "YES" : "NO");
-
-    // Should we squeeze or not?  Arbitrary heuristic: we squeeze if
-    // the number of words we have to shift down is less than the
-    // number of stack words we squeeze away by doing so.
-    if (RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue &&
-	weight < words_to_squeeze) {
-	stackSqueeze(tso, (StgPtr)frame);
-    }
-}
-
-/* -----------------------------------------------------------------------------
- * Debugging
- * -------------------------------------------------------------------------- */
-
-#if DEBUG
-void
-printMutableList(generation *gen)
-{
-    bdescr *bd;
-    StgPtr p;
-
-    debugBelch("mutable list %p: ", gen->mut_list);
-
-    for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
-	for (p = bd->start; p < bd->free; p++) {
-	    debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));
-	}
-    }
-    debugBelch("\n");
-}
-#endif /* DEBUG */
diff --git a/rts/HCIncludes.h b/rts/HCIncludes.h
index 06cc61a8a5..e74114bcc3 100644
--- a/rts/HCIncludes.h
+++ b/rts/HCIncludes.h
@@ -3,11 +3,11 @@
 #include "RtsFlags.h"
 #include "RtsUtils.h"
 #include "StgRun.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "Printer.h"
 #include "Sanity.h"
 #include "STM.h"
-#include "Storage.h"
 #include "SchedAPI.h"
 #include "Timer.h"
 #include "ProfHeap.h"
@@ -20,3 +20,4 @@
 #include "ThreadLabels.h"
 #include "Threads.h"
 #include "Prelude.h"
+#include "Stable.h"
diff --git a/rts/HsFFI.c b/rts/HsFFI.c
index 350bcfbdec..d59c7a40a3 100644
--- a/rts/HsFFI.c
+++ b/rts/HsFFI.c
@@ -8,6 +8,8 @@
 
 #include "HsFFI.h"
 #include "Rts.h"
+#include "Storage.h"
+#include "Stable.h"
 
 // hs_init and hs_exit are defined in RtsStartup.c
 
diff --git a/rts/Interpreter.c b/rts/Interpreter.c
index 94a0286167..62fe50530e 100644
--- a/rts/Interpreter.c
+++ b/rts/Interpreter.c
@@ -10,9 +10,9 @@
 #include "RtsUtils.h"
 #include "Closures.h"
 #include "TSO.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "RtsFlags.h"
-#include "Storage.h"
 #include "LdvProfile.h"
 #include "Updates.h"
 #include "Sanity.h"
diff --git a/rts/Linker.c b/rts/Linker.c
index b6e8249abd..107db26e1e 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -21,11 +21,12 @@
 #include "RtsFlags.h"
 #include "HsFFI.h"
 #include "Hash.h"
+#include "Storage.h"
+#include "Stable.h"
 #include "Linker.h"
 #include "LinkerInternals.h"
 #include "RtsUtils.h"
 #include "Schedule.h"
-#include "Storage.h"
 #include "Sparks.h"
 #include "RtsTypeable.h"
 
diff --git a/rts/Main.c b/rts/Main.c
index 5a1ab10927..6738a1cbb9 100644
--- a/rts/Main.c
+++ b/rts/Main.c
@@ -12,7 +12,6 @@
 #include "Rts.h"
 #include "RtsAPI.h"
 #include "SchedAPI.h"
-#include "Schedule.h"
 #include "RtsFlags.h"
 #include "RtsUtils.h"
 #include "Prelude.h"
diff --git a/rts/Makefile b/rts/Makefile
index d187547c39..c01a907fdd 100644
--- a/rts/Makefile
+++ b/rts/Makefile
@@ -44,7 +44,7 @@ endif
 NON_HS_PACKAGE = YES
 
 # grab sources from these subdirectories
-ALL_DIRS = hooks parallel
+ALL_DIRS = hooks parallel sm
 
 ifeq "$(HOSTPLATFORM)" "i386-unknown-mingw32"
 ALL_DIRS += win32
@@ -88,7 +88,7 @@ H_FILES = $(wildcard ../includes/*.h) $(wildcard *.h)
 # gcc provides lots of useful warnings if you ask it.
 # This is a pretty good list to start with - use a # to comment out
 # any you don't like.
-WARNING_OPTS += -Wall 
+WARNING_OPTS += -Wall
 WARNING_OPTS += -W
 WARNING_OPTS += -Wstrict-prototypes 
 WARNING_OPTS += -Wmissing-prototypes 
@@ -105,7 +105,7 @@ WARNING_OPTS += -Wbad-function-cast
 #WARNING_OPTS += -Wredundant-decls 
 #WARNING_OPTS += -Wconversion
 
-STANDARD_OPTS += -I../includes -I. -Iparallel
+STANDARD_OPTS += -I../includes -I. -Iparallel -Ism
 # COMPILING_RTS is only used when building Win32 DLL support.
 STANDARD_OPTS += -DCOMPILING_RTS
 
diff --git a/rts/RaiseAsync.c b/rts/RaiseAsync.c
index 0f84ae5360..4a405e7b49 100644
--- a/rts/RaiseAsync.c
+++ b/rts/RaiseAsync.c
@@ -12,8 +12,8 @@
 #include "Trace.h"
 #include "RaiseAsync.h"
 #include "SMP.h"
-#include "Schedule.h"
 #include "Storage.h"
+#include "Schedule.h"
 #include "LdvProfile.h"
 #include "Updates.h"
 #include "STM.h"
diff --git a/rts/RaiseAsync.h b/rts/RaiseAsync.h
index 8e59d51d9f..3ab96abac2 100644
--- a/rts/RaiseAsync.h
+++ b/rts/RaiseAsync.h
@@ -45,7 +45,7 @@ void awakenBlockedExceptionQueue  (Capability *cap, StgTSO *tso);
  * indefinitely).  Interruptible threads can be sent an exception with
  * killThread# even if they have async exceptions blocked.
  */
-STATIC_INLINE int
+INLINE_HEADER int
 interruptible(StgTSO *t)
 {
   switch (t->why_blocked) {
diff --git a/rts/RetainerProfile.c b/rts/RetainerProfile.c
index e63fb54978..cd0001311d 100644
--- a/rts/RetainerProfile.c
+++ b/rts/RetainerProfile.c
@@ -20,15 +20,15 @@
 #include "RtsUtils.h"
 #include "RetainerProfile.h"
 #include "RetainerSet.h"
+#include "Storage.h"
 #include "Schedule.h"
+#include "Stable.h"
 #include "Printer.h"
-#include "Storage.h"
 #include "RtsFlags.h"
 #include "Weak.h"
 #include "Sanity.h"
 #include "Profiling.h"
 #include "Stats.h"
-#include "BlockAlloc.h"
 #include "ProfHeap.h"
 #include "Apply.h"
 
diff --git a/rts/RtsAPI.c b/rts/RtsAPI.c
index b1b1d9c52d..1a18e9bf7b 100644
--- a/rts/RtsAPI.c
+++ b/rts/RtsAPI.c
@@ -17,6 +17,7 @@
 #include "Prelude.h"
 #include "Schedule.h"
 #include "Capability.h"
+#include "Stable.h"
 
 #include <stdlib.h>
 
diff --git a/rts/RtsFlags.c b/rts/RtsFlags.c
index e439afe00c..9aa906f130 100644
--- a/rts/RtsFlags.c
+++ b/rts/RtsFlags.c
@@ -11,7 +11,6 @@
 #include "Rts.h"
 #include "RtsFlags.h"
 #include "RtsUtils.h"
-#include "BlockAlloc.h"
 #include "Profiling.h"
 
 #ifdef HAVE_CTYPE_H
diff --git a/rts/RtsStartup.c b/rts/RtsStartup.c
index 62a347a44d..f023a96092 100644
--- a/rts/RtsStartup.c
+++ b/rts/RtsStartup.c
@@ -29,6 +29,7 @@
 #include "BlockAlloc.h"
 #include "Trace.h"
 #include "RtsTypeable.h"
+#include "Stable.h"
 
 #if defined(RTS_GTK_FRONTPANEL)
 #include "FrontPanel.h"
diff --git a/rts/STM.c b/rts/STM.c
index d840f4ebfe..f9c814f0e0 100644
--- a/rts/STM.c
+++ b/rts/STM.c
@@ -86,10 +86,10 @@
 #include "Rts.h"
 #include "RtsFlags.h"
 #include "RtsUtils.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "SMP.h"
 #include "STM.h"
-#include "Storage.h"
 #include "Trace.h"
 
 #include <stdlib.h>
diff --git a/rts/Schedule.c b/rts/Schedule.c
index 571d02beb2..0a46ec5144 100644
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -11,7 +11,6 @@
 #include "SchedAPI.h"
 #include "RtsUtils.h"
 #include "RtsFlags.h"
-#include "BlockAlloc.h"
 #include "OSThreads.h"
 #include "Storage.h"
 #include "StgRun.h"
@@ -218,11 +217,9 @@ static rtsBool scheduleHandleThreadFinished( Capability *cap, Task *task,
 					     StgTSO *t );
 static rtsBool scheduleDoHeapProfile(rtsBool ready_to_gc);
 static Capability *scheduleDoGC(Capability *cap, Task *task,
-				rtsBool force_major, 
-				void (*get_roots)(evac_fn));
+				rtsBool force_major);
 
 static rtsBool checkBlackHoles(Capability *cap);
-static void AllRoots(evac_fn evac);
 
 static StgTSO *threadStackOverflow(Capability *cap, StgTSO *tso);
 
@@ -421,7 +418,7 @@ schedule (Capability *initialCapability, Task *task)
 	discardSparksCap(cap);
 #endif
 	/* scheduleDoGC() deletes all the threads */
-	cap = scheduleDoGC(cap,task,rtsFalse,GetRoots);
+	cap = scheduleDoGC(cap,task,rtsFalse);
 	break;
     case SCHED_SHUTTING_DOWN:
 	debugTrace(DEBUG_sched, "SCHED_SHUTTING_DOWN");
@@ -701,7 +698,7 @@ run_thread:
 
     if (scheduleDoHeapProfile(ready_to_gc)) { ready_to_gc = rtsFalse; }
     if (ready_to_gc) {
-      cap = scheduleDoGC(cap,task,rtsFalse,GetRoots);
+      cap = scheduleDoGC(cap,task,rtsFalse);
     }
   } /* end of while() */
 
@@ -968,7 +965,7 @@ scheduleDetectDeadlock (Capability *cap, Task *task)
 	// they are unreachable and will therefore be sent an
 	// exception.  Any threads thus released will be immediately
 	// runnable.
-	cap = scheduleDoGC (cap, task, rtsTrue/*force  major GC*/, GetRoots);
+	cap = scheduleDoGC (cap, task, rtsTrue/*force  major GC*/);
 
 	recent_activity = ACTIVITY_DONE_GC;
 	
@@ -1929,7 +1926,7 @@ scheduleDoHeapProfile( rtsBool ready_to_gc STG_UNUSED )
 	scheduleCheckBlackHoles(&MainCapability);
 
 	debugTrace(DEBUG_sched, "garbage collecting before heap census");
-	GarbageCollect(GetRoots, rtsTrue);
+	GarbageCollect(rtsTrue);
 
 	debugTrace(DEBUG_sched, "performing heap census");
 	heapCensus();
@@ -1946,8 +1943,7 @@ scheduleDoHeapProfile( rtsBool ready_to_gc STG_UNUSED )
  * -------------------------------------------------------------------------- */
 
 static Capability *
-scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS,
-	      rtsBool force_major, void (*get_roots)(evac_fn))
+scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS, rtsBool force_major)
 {
     StgTSO *t;
 #ifdef THREADED_RTS
@@ -2066,7 +2062,7 @@ scheduleDoGC (Capability *cap, Task *task USED_IF_THREADS,
 #if defined(THREADED_RTS)
     debugTrace(DEBUG_sched, "doing GC");
 #endif
-    GarbageCollect(get_roots, force_major);
+    GarbageCollect(force_major);
     
 #if defined(THREADED_RTS)
     // release our stash of capabilities.
@@ -2567,7 +2563,7 @@ exitScheduler( void )
     // If we haven't killed all the threads yet, do it now.
     if (sched_state < SCHED_SHUTTING_DOWN) {
 	sched_state = SCHED_INTERRUPTING;
-	scheduleDoGC(NULL,task,rtsFalse,GetRoots);    
+	scheduleDoGC(NULL,task,rtsFalse);    
     }
     sched_state = SCHED_SHUTTING_DOWN;
 
@@ -2672,10 +2668,8 @@ GetRoots( evac_fn evac )
    collect when called from Haskell via _ccall_GC.
    -------------------------------------------------------------------------- */
 
-static void (*extra_roots)(evac_fn);
-
 static void
-performGC_(rtsBool force_major, void (*get_roots)(evac_fn))
+performGC_(rtsBool force_major)
 {
     Task *task;
     // We must grab a new Task here, because the existing Task may be
@@ -2684,27 +2678,20 @@ performGC_(rtsBool force_major, void (*get_roots)(evac_fn))
     ACQUIRE_LOCK(&sched_mutex);
     task = newBoundTask();
     RELEASE_LOCK(&sched_mutex);
-    scheduleDoGC(NULL,task,force_major, get_roots);
+    scheduleDoGC(NULL,task,force_major);
     boundTaskExiting(task);
 }
 
 void
 performGC(void)
 {
-    performGC_(rtsFalse, GetRoots);
+    performGC_(rtsFalse);
 }
 
 void
 performMajorGC(void)
 {
-    performGC_(rtsTrue, GetRoots);
-}
-
-static void
-AllRoots(evac_fn evac)
-{
-    GetRoots(evac);		// the scheduler's roots
-    extra_roots(evac);		// the user's roots
+    performGC_(rtsTrue);
 }
 
 /* -----------------------------------------------------------------------------
diff --git a/rts/Schedule.h b/rts/Schedule.h
index f82946e831..2afedeec86 100644
--- a/rts/Schedule.h
+++ b/rts/Schedule.h
@@ -191,7 +191,7 @@ void print_bqe (StgBlockingQueueElement *bqe);
  * NOTE: tso->link should be END_TSO_QUEUE before calling this macro.
  * ASSUMES: cap->running_task is the current task.
  */
-STATIC_INLINE void
+INLINE_HEADER void
 appendToRunQueue (Capability *cap, StgTSO *tso)
 {
     ASSERT(tso->link == END_TSO_QUEUE);
@@ -207,7 +207,7 @@ appendToRunQueue (Capability *cap, StgTSO *tso)
  * newly awakened threads, so they get run as soon as possible.
  * ASSUMES: cap->running_task is the current task.
  */
-STATIC_INLINE void
+INLINE_HEADER void
 pushOnRunQueue (Capability *cap, StgTSO *tso)
 {
     tso->link = cap->run_queue_hd;
@@ -219,7 +219,7 @@ pushOnRunQueue (Capability *cap, StgTSO *tso)
 
 /* Pop the first thread off the runnable queue.
  */
-STATIC_INLINE StgTSO *
+INLINE_HEADER StgTSO *
 popRunQueue (Capability *cap)
 { 
     StgTSO *t = cap->run_queue_hd;
@@ -235,7 +235,7 @@ popRunQueue (Capability *cap)
 /* Add a thread to the end of the blocked queue.
  */
 #if !defined(THREADED_RTS)
-STATIC_INLINE void
+INLINE_HEADER void
 appendToBlockedQueue(StgTSO *tso)
 {
     ASSERT(tso->link == END_TSO_QUEUE);
@@ -249,7 +249,7 @@ appendToBlockedQueue(StgTSO *tso)
 #endif
 
 #if defined(THREADED_RTS)
-STATIC_INLINE void
+INLINE_HEADER void
 appendToWakeupQueue (Capability *cap, StgTSO *tso)
 {
     ASSERT(tso->link == END_TSO_QUEUE);
@@ -264,20 +264,20 @@ appendToWakeupQueue (Capability *cap, StgTSO *tso)
 
 /* Check whether various thread queues are empty
  */
-STATIC_INLINE rtsBool
+INLINE_HEADER rtsBool
 emptyQueue (StgTSO *q)
 {
     return (q == END_TSO_QUEUE);
 }
 
-STATIC_INLINE rtsBool
+INLINE_HEADER rtsBool
 emptyRunQueue(Capability *cap)
 {
     return emptyQueue(cap->run_queue_hd);
 }
 
 #if defined(THREADED_RTS)
-STATIC_INLINE rtsBool
+INLINE_HEADER rtsBool
 emptyWakeupQueue(Capability *cap)
 {
     return emptyQueue(cap->wakeup_queue_hd);
@@ -289,7 +289,7 @@ emptyWakeupQueue(Capability *cap)
 #define EMPTY_SLEEPING_QUEUE() (emptyQueue(sleeping_queue))
 #endif
 
-STATIC_INLINE rtsBool
+INLINE_HEADER rtsBool
 emptyThreadQueues(Capability *cap)
 {
     return emptyRunQueue(cap)
@@ -301,7 +301,7 @@ emptyThreadQueues(Capability *cap)
 
 #endif /* !IN_STG_CODE */
 
-STATIC_INLINE void
+INLINE_HEADER void
 dirtyTSO (StgTSO *tso)
 {
     tso->flags |= TSO_DIRTY;
diff --git a/rts/Sparks.c b/rts/Sparks.c
index c7a1c9f98a..40ebcad7a7 100644
--- a/rts/Sparks.c
+++ b/rts/Sparks.c
@@ -8,9 +8,9 @@
 
 #include "PosixSource.h"
 #include "Rts.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "SchedAPI.h"
-#include "Storage.h"
 #include "RtsFlags.h"
 #include "RtsUtils.h"
 #include "ParTicky.h"
diff --git a/rts/Stable.c b/rts/Stable.c
index 813c6c8b47..e5e8dfbdd0 100644
--- a/rts/Stable.c
+++ b/rts/Stable.c
@@ -19,6 +19,7 @@
 #include "RtsFlags.h"
 #include "OSThreads.h"
 #include "Trace.h"
+#include "Stable.h"
 
 /* Comment from ADR's implementation in old RTS:
 
diff --git a/rts/Stats.c b/rts/Stats.c
index 248b0af58a..6e093adb53 100644
--- a/rts/Stats.c
+++ b/rts/Stats.c
@@ -10,11 +10,11 @@
 #include "RtsFlags.h"
 #include "RtsUtils.h"
 #include "MBlock.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "Stats.h"
 #include "ParTicky.h"                       /* ToDo: move into Rts.h */
 #include "Profiling.h"
-#include "Storage.h"
 #include "GetTime.h"
 
 /* huh? */
diff --git a/rts/Task.c b/rts/Task.c
index 11307a7703..588d414d87 100644
--- a/rts/Task.c
+++ b/rts/Task.c
@@ -15,6 +15,7 @@
 #include "Capability.h"
 #include "Stats.h"
 #include "RtsFlags.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "Hash.h"
 #include "Trace.h"
diff --git a/rts/ThreadPaused.c b/rts/ThreadPaused.c
new file mode 100644
index 0000000000..f7017042f6
--- /dev/null
+++ b/rts/ThreadPaused.c
@@ -0,0 +1,290 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Tidying up a thread when it stops running
+ *
+ * ---------------------------------------------------------------------------*/
+
+#include "Rts.h"
+#include "Storage.h"
+#include "Updates.h"
+#include "RaiseAsync.h"
+#include "Trace.h"
+#include "RtsFlags.h"
+
+#include <string.h> // for memmove()
+
+/* -----------------------------------------------------------------------------
+ * Stack squeezing
+ *
+ * Code largely pinched from old RTS, then hacked to bits.  We also do
+ * lazy black holing here.
+ *
+ * -------------------------------------------------------------------------- */
+
+struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
+
+static void
+stackSqueeze(StgTSO *tso, StgPtr bottom)
+{
+    StgPtr frame;
+    rtsBool prev_was_update_frame;
+    StgClosure *updatee = NULL;
+    StgRetInfoTable *info;
+    StgWord current_gap_size;
+    struct stack_gap *gap;
+
+    // Stage 1: 
+    //    Traverse the stack upwards, replacing adjacent update frames
+    //    with a single update frame and a "stack gap".  A stack gap
+    //    contains two values: the size of the gap, and the distance
+    //    to the next gap (or the stack top).
+
+    frame = tso->sp;
+
+    ASSERT(frame < bottom);
+    
+    prev_was_update_frame = rtsFalse;
+    current_gap_size = 0;
+    gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
+
+    while (frame < bottom) {
+	
+	info = get_ret_itbl((StgClosure *)frame);
+	switch (info->i.type) {
+
+	case UPDATE_FRAME:
+	{ 
+	    StgUpdateFrame *upd = (StgUpdateFrame *)frame;
+
+	    if (prev_was_update_frame) {
+
+		TICK_UPD_SQUEEZED();
+		/* wasn't there something about update squeezing and ticky to be
+		 * sorted out?  oh yes: we aren't counting each enter properly
+		 * in this case.  See the log somewhere.  KSW 1999-04-21
+		 *
+		 * Check two things: that the two update frames don't point to
+		 * the same object, and that the updatee_bypass isn't already an
+		 * indirection.  Both of these cases only happen when we're in a
+		 * block hole-style loop (and there are multiple update frames
+		 * on the stack pointing to the same closure), but they can both
+		 * screw us up if we don't check.
+		 */
+		if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
+		    UPD_IND_NOLOCK(upd->updatee, updatee);
+		}
+
+		// now mark this update frame as a stack gap.  The gap
+		// marker resides in the bottom-most update frame of
+		// the series of adjacent frames, and covers all the
+		// frames in this series.
+		current_gap_size += sizeofW(StgUpdateFrame);
+		((struct stack_gap *)frame)->gap_size = current_gap_size;
+		((struct stack_gap *)frame)->next_gap = gap;
+
+		frame += sizeofW(StgUpdateFrame);
+		continue;
+	    } 
+
+	    // single update frame, or the topmost update frame in a series
+	    else {
+		prev_was_update_frame = rtsTrue;
+		updatee = upd->updatee;
+		frame += sizeofW(StgUpdateFrame);
+		continue;
+	    }
+	}
+	    
+	default:
+	    prev_was_update_frame = rtsFalse;
+
+	    // we're not in a gap... check whether this is the end of a gap
+	    // (an update frame can't be the end of a gap).
+	    if (current_gap_size != 0) {
+		gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
+	    }
+	    current_gap_size = 0;
+
+	    frame += stack_frame_sizeW((StgClosure *)frame);
+	    continue;
+	}
+    }
+
+    if (current_gap_size != 0) {
+	gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
+    }
+
+    // Now we have a stack with gaps in it, and we have to walk down
+    // shoving the stack up to fill in the gaps.  A diagram might
+    // help:
+    //
+    //    +| ********* |
+    //     | ********* | <- sp
+    //     |           |
+    //     |           | <- gap_start
+    //     | ......... |                |
+    //     | stack_gap | <- gap         | chunk_size
+    //     | ......... |                | 
+    //     | ......... | <- gap_end     v
+    //     | ********* | 
+    //     | ********* | 
+    //     | ********* | 
+    //    -| ********* | 
+    //
+    // 'sp'  points the the current top-of-stack
+    // 'gap' points to the stack_gap structure inside the gap
+    // *****   indicates real stack data
+    // .....   indicates gap
+    // <empty> indicates unused
+    //
+    {
+	void *sp;
+	void *gap_start, *next_gap_start, *gap_end;
+	nat chunk_size;
+
+	next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
+	sp = next_gap_start;
+
+	while ((StgPtr)gap > tso->sp) {
+
+	    // we're working in *bytes* now...
+	    gap_start = next_gap_start;
+	    gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
+
+	    gap = gap->next_gap;
+	    next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
+
+	    chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
+	    sp -= chunk_size;
+	    memmove(sp, next_gap_start, chunk_size);
+	}
+
+	tso->sp = (StgPtr)sp;
+    }
+}    
+
+/* -----------------------------------------------------------------------------
+ * Pausing a thread
+ * 
+ * We have to prepare for GC - this means doing lazy black holing
+ * here.  We also take the opportunity to do stack squeezing if it's
+ * turned on.
+ * -------------------------------------------------------------------------- */
+void
+threadPaused(Capability *cap, StgTSO *tso)
+{
+    StgClosure *frame;
+    StgRetInfoTable *info;
+    StgClosure *bh;
+    StgPtr stack_end;
+    nat words_to_squeeze = 0;
+    nat weight           = 0;
+    nat weight_pending   = 0;
+    rtsBool prev_was_update_frame = rtsFalse;
+    
+    // Check to see whether we have threads waiting to raise
+    // exceptions, and we're not blocking exceptions, or are blocked
+    // interruptibly.  This is important; if a thread is running with
+    // TSO_BLOCKEX and becomes blocked interruptibly, this is the only
+    // place we ensure that the blocked_exceptions get a chance.
+    maybePerformBlockedException (cap, tso);
+    if (tso->what_next == ThreadKilled) { return; }
+
+    stack_end = &tso->stack[tso->stack_size];
+    
+    frame = (StgClosure *)tso->sp;
+
+    while (1) {
+	// If we've already marked this frame, then stop here.
+	if (frame->header.info == (StgInfoTable *)&stg_marked_upd_frame_info) {
+	    goto end;
+	}
+
+	info = get_ret_itbl(frame);
+	
+	switch (info->i.type) {
+	    
+	case UPDATE_FRAME:
+
+	    SET_INFO(frame, (StgInfoTable *)&stg_marked_upd_frame_info);
+
+	    bh = ((StgUpdateFrame *)frame)->updatee;
+
+	    if (closure_IND(bh) || bh->header.info == &stg_BLACKHOLE_info) {
+		debugTrace(DEBUG_squeeze,
+			   "suspending duplicate work: %ld words of stack",
+			   (long)((StgPtr)frame - tso->sp));
+
+		// If this closure is already an indirection, then
+		// suspend the computation up to this point:
+		suspendComputation(cap,tso,(StgPtr)frame);
+
+		// Now drop the update frame, and arrange to return
+		// the value to the frame underneath:
+		tso->sp = (StgPtr)frame + sizeofW(StgUpdateFrame) - 2;
+		tso->sp[1] = (StgWord)bh;
+		tso->sp[0] = (W_)&stg_enter_info;
+
+		// And continue with threadPaused; there might be
+		// yet more computation to suspend.
+		threadPaused(cap,tso);
+		return;
+	    }
+
+	    if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
+#if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
+		debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh);
+#endif
+		// zero out the slop so that the sanity checker can tell
+		// where the next closure is.
+		DEBUG_FILL_SLOP(bh);
+#ifdef PROFILING
+		// @LDV profiling
+		// We pretend that bh is now dead.
+		LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
+#endif
+		SET_INFO(bh,&stg_BLACKHOLE_info);
+
+		// We pretend that bh has just been created.
+		LDV_RECORD_CREATE(bh);
+	    }
+	    
+	    frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
+	    if (prev_was_update_frame) {
+		words_to_squeeze += sizeofW(StgUpdateFrame);
+		weight += weight_pending;
+		weight_pending = 0;
+	    }
+	    prev_was_update_frame = rtsTrue;
+	    break;
+	    
+	case STOP_FRAME:
+	    goto end;
+	    
+	    // normal stack frames; do nothing except advance the pointer
+	default:
+	{
+	    nat frame_size = stack_frame_sizeW(frame);
+	    weight_pending += frame_size;
+	    frame = (StgClosure *)((StgPtr)frame + frame_size);
+	    prev_was_update_frame = rtsFalse;
+	}
+	}
+    }
+
+end:
+    debugTrace(DEBUG_squeeze, 
+	       "words_to_squeeze: %d, weight: %d, squeeze: %s", 
+	       words_to_squeeze, weight, 
+	       weight < words_to_squeeze ? "YES" : "NO");
+
+    // Should we squeeze or not?  Arbitrary heuristic: we squeeze if
+    // the number of words we have to shift down is less than the
+    // number of stack words we squeeze away by doing so.
+    if (RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue &&
+	weight < words_to_squeeze) {
+	stackSqueeze(tso, (StgPtr)frame);
+    }
+}
diff --git a/rts/Timer.c b/rts/Timer.c
index d56fdb656f..8088600246 100644
--- a/rts/Timer.c
+++ b/rts/Timer.c
@@ -17,6 +17,7 @@
 #include "Rts.h"
 #include "RtsFlags.h"
 #include "Proftimer.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "Timer.h"
 #include "Ticker.h"
diff --git a/rts/Typeable.c b/rts/Typeable.c
index 1d7edd1c94..e0309d63d7 100644
--- a/rts/Typeable.c
+++ b/rts/Typeable.c
@@ -1,5 +1,15 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 1995-2005
+ *
+ * Data.Typeable support
+ *
+ * ---------------------------------------------------------------------------*/
+
 #include "RtsTypeable.h"
 #include "Rts.h"
+#include "Storage.h"
+#include "Stable.h"
 
 static StgPtr typeableStore = 0;
 #ifdef THREADED_RTS
diff --git a/rts/parallel/GranSim.c b/rts/parallel/GranSim.c
index b1cc0962be..1b26bb9dff 100644
--- a/rts/parallel/GranSim.c
+++ b/rts/parallel/GranSim.c
@@ -1,5 +1,5 @@
 /* 
-   Time-stamp: <Tue Mar 06 2001 00:17:42 Stardate: [-30]6285.06 hwloidl>
+   Time-stamp: <2006-10-19 15:12:58 simonmar>
 
    Variables and functions specific to GranSim the parallelism simulator
    for GPH.
@@ -45,6 +45,7 @@
 #include "RtsUtils.h"
 #include "StgMiscClosures.h"
 #include "StgTypes.h"
+#include "Storage.h"       // for recordMutable
 #include "Schedule.h"
 #include "SchedAPI.h"       // for pushClosure
 #include "GranSimRts.h"
@@ -52,7 +53,6 @@
 #include "ParallelRts.h"
 #include "ParallelDebug.h"
 #include "Sparks.h"
-#include "Storage.h"       // for recordMutable
 
 
 //@node Prototypes and externs, Constants and Variables, Includes, GranSim specific code
diff --git a/rts/posix/Itimer.c b/rts/posix/Itimer.c
index 0f0b1e977e..715cf5af3c 100644
--- a/rts/posix/Itimer.c
+++ b/rts/posix/Itimer.c
@@ -22,6 +22,7 @@
 #include "Ticker.h"
 #include "posix/Itimer.h"
 #include "Proftimer.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "posix/Select.h"
 
diff --git a/rts/posix/Select.c b/rts/posix/Select.c
index ccf39458d2..bb65310c9e 100644
--- a/rts/posix/Select.c
+++ b/rts/posix/Select.c
@@ -10,6 +10,7 @@
 /* #include "PosixSource.h" */
 
 #include "Rts.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "RtsUtils.h"
 #include "RtsFlags.h"
diff --git a/rts/posix/Signals.c b/rts/posix/Signals.c
index a5044cd6de..ded85f5d39 100644
--- a/rts/posix/Signals.c
+++ b/rts/posix/Signals.c
@@ -11,12 +11,14 @@
 */
 #include "Rts.h"
 #include "SchedAPI.h"
+#include "Storage.h"
 #include "Schedule.h"
 #include "RtsSignals.h"
 #include "posix/Signals.h"
 #include "RtsUtils.h"
 #include "RtsFlags.h"
 #include "Prelude.h"
+#include "Stable.h"
 
 #ifdef alpha_HOST_ARCH
 # if defined(linux_HOST_OS)
diff --git a/rts/BlockAlloc.c b/rts/sm/BlockAlloc.c
index d2f08eeb62..d2f08eeb62 100644
--- a/rts/BlockAlloc.c
+++ b/rts/sm/BlockAlloc.c
diff --git a/rts/BlockAlloc.h b/rts/sm/BlockAlloc.h
index 1472ac6f76..1472ac6f76 100644
--- a/rts/BlockAlloc.h
+++ b/rts/sm/BlockAlloc.h
diff --git a/rts/GCCompact.c b/rts/sm/Compact.c
index da3c7a7c62..f50c994da8 100644
--- a/rts/GCCompact.c
+++ b/rts/sm/Compact.c
@@ -12,9 +12,11 @@
 #include "RtsFlags.h"
 #include "OSThreads.h"
 #include "Storage.h"
+#include "Stable.h"
 #include "BlockAlloc.h"
 #include "MBlock.h"
-#include "GCCompact.h"
+#include "GC.h"
+#include "Compact.h"
 #include "Schedule.h"
 #include "Apply.h"
 #include "Trace.h"
@@ -476,7 +478,8 @@ update_fwd_large( bdescr *bd )
   }
 }
 
-STATIC_INLINE StgPtr
+// ToDo: too big to inline
+static /* STATIC_INLINE */ StgPtr
 thread_obj (StgInfoTable *info, StgPtr p)
 {
     switch (info->type) {
@@ -891,13 +894,13 @@ update_bkwd_compact( step *stp )
 }
 
 void
-compact( void (*get_roots)(evac_fn) )
+compact(void)
 {
     nat g, s, blocks;
     step *stp;
 
     // 1. thread the roots
-    get_roots((evac_fn)thread);
+    GetRoots((evac_fn)thread);
 
     // the weak pointer lists...
     if (weak_ptr_list != NULL) {
diff --git a/rts/GCCompact.h b/rts/sm/Compact.h
index 0fb39b3b12..4f1d6a27c7 100644
--- a/rts/GCCompact.h
+++ b/rts/sm/Compact.h
@@ -9,7 +9,37 @@
 #ifndef GCCOMPACT_H
 #define GCCOMPACT_H
 
-STATIC_INLINE void 
+INLINE_HEADER rtsBool
+mark_stack_empty(void)
+{
+    return mark_sp == mark_stack;
+}
+
+INLINE_HEADER rtsBool
+mark_stack_full(void)
+{
+    return mark_sp >= mark_splim;
+}
+
+INLINE_HEADER void
+reset_mark_stack(void)
+{
+    mark_sp = mark_stack;
+}
+
+INLINE_HEADER void
+push_mark_stack(StgPtr p)
+{
+    *mark_sp++ = p;
+}
+
+INLINE_HEADER StgPtr
+pop_mark_stack(void)
+{
+    return *--mark_sp;
+}
+
+INLINE_HEADER void 
 mark(StgPtr p, bdescr *bd)
 {
     nat offset_within_block = p - bd->start; // in words
@@ -19,7 +49,7 @@ mark(StgPtr p, bdescr *bd)
     *bitmap_word |= bit_mask;
 }
 
-STATIC_INLINE void 
+INLINE_HEADER void 
 unmark(StgPtr p, bdescr *bd)
 {
     nat offset_within_block = p - bd->start; // in words
@@ -29,7 +59,7 @@ unmark(StgPtr p, bdescr *bd)
     *bitmap_word &= ~bit_mask;
 }
 
-STATIC_INLINE StgWord
+INLINE_HEADER StgWord
 is_marked(StgPtr p, bdescr *bd)
 {
     nat offset_within_block = p - bd->start; // in words
@@ -39,6 +69,6 @@ is_marked(StgPtr p, bdescr *bd)
     return (*bitmap_word & bit_mask);
 }
 
-void compact( void (*get_roots)(evac_fn) );
+void compact(void);
 
 #endif /* GCCOMPACT_H */
diff --git a/rts/sm/Evac.c b/rts/sm/Evac.c
new file mode 100644
index 0000000000..9d1c4602ef
--- /dev/null
+++ b/rts/sm/Evac.c
@@ -0,0 +1,967 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Generational garbage collector: evacuation functions
+ *
+ * ---------------------------------------------------------------------------*/
+
+#include "Rts.h"
+#include "Storage.h"
+#include "MBlock.h"
+#include "Evac.h"
+#include "GC.h"
+#include "GCUtils.h"
+#include "Compact.h"
+#include "Prelude.h"
+#include "LdvProfile.h"
+
+/* Used to avoid long recursion due to selector thunks
+ */
+lnat thunk_selector_depth = 0;
+#define MAX_THUNK_SELECTOR_DEPTH 8
+
+static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
+
+STATIC_INLINE void 
+upd_evacuee(StgClosure *p, StgClosure *dest)
+{
+    // not true: (ToDo: perhaps it should be)
+    // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
+    SET_INFO(p, &stg_EVACUATED_info);
+    ((StgEvacuated *)p)->evacuee = dest;
+}
+
+
+STATIC_INLINE StgClosure *
+copy(StgClosure *src, nat size, step *stp)
+{
+  StgPtr to, from;
+  nat i;
+#ifdef PROFILING
+  // @LDV profiling
+  nat size_org = size;
+#endif
+
+  TICK_GC_WORDS_COPIED(size);
+  /* Find out where we're going, using the handy "to" pointer in 
+   * the step of the source object.  If it turns out we need to
+   * evacuate to an older generation, adjust it here (see comment
+   * by evacuate()).
+   */
+  if (stp->gen_no < evac_gen) {
+      if (eager_promotion) {
+	  stp = &generations[evac_gen].steps[0];
+      } else {
+	  failed_to_evac = rtsTrue;
+      }
+  }
+
+  /* chain a new block onto the to-space for the destination step if
+   * necessary.
+   */
+  if (stp->hp + size >= stp->hpLim) {
+    gc_alloc_block(stp);
+  }
+
+  to = stp->hp;
+  from = (StgPtr)src;
+  stp->hp = to + size;
+  for (i = 0; i < size; i++) { // unroll for small i
+      to[i] = from[i];
+  }
+  upd_evacuee((StgClosure *)from,(StgClosure *)to);
+
+#ifdef PROFILING
+  // We store the size of the just evacuated object in the LDV word so that
+  // the profiler can guess the position of the next object later.
+  SET_EVACUAEE_FOR_LDV(from, size_org);
+#endif
+  return (StgClosure *)to;
+}
+
+// Same as copy() above, except the object will be allocated in memory
+// that will not be scavenged.  Used for object that have no pointer
+// fields.
+STATIC_INLINE StgClosure *
+copy_noscav(StgClosure *src, nat size, step *stp)
+{
+  StgPtr to, from;
+  nat i;
+#ifdef PROFILING
+  // @LDV profiling
+  nat size_org = size;
+#endif
+
+  TICK_GC_WORDS_COPIED(size);
+  /* Find out where we're going, using the handy "to" pointer in 
+   * the step of the source object.  If it turns out we need to
+   * evacuate to an older generation, adjust it here (see comment
+   * by evacuate()).
+   */
+  if (stp->gen_no < evac_gen) {
+      if (eager_promotion) {
+	  stp = &generations[evac_gen].steps[0];
+      } else {
+	  failed_to_evac = rtsTrue;
+      }
+  }
+
+  /* chain a new block onto the to-space for the destination step if
+   * necessary.
+   */
+  if (stp->scavd_hp + size >= stp->scavd_hpLim) {
+    gc_alloc_scavd_block(stp);
+  }
+
+  to = stp->scavd_hp;
+  from = (StgPtr)src;
+  stp->scavd_hp = to + size;
+  for (i = 0; i < size; i++) { // unroll for small i
+      to[i] = from[i];
+  }
+  upd_evacuee((StgClosure *)from,(StgClosure *)to);
+
+#ifdef PROFILING
+  // We store the size of the just evacuated object in the LDV word so that
+  // the profiler can guess the position of the next object later.
+  SET_EVACUAEE_FOR_LDV(from, size_org);
+#endif
+  return (StgClosure *)to;
+}
+
+/* Special version of copy() for when we only want to copy the info
+ * pointer of an object, but reserve some padding after it.  This is
+ * used to optimise evacuation of BLACKHOLEs.
+ */
+
+
+static StgClosure *
+copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
+{
+  P_ dest, to, from;
+#ifdef PROFILING
+  // @LDV profiling
+  nat size_to_copy_org = size_to_copy;
+#endif
+
+  TICK_GC_WORDS_COPIED(size_to_copy);
+  if (stp->gen_no < evac_gen) {
+      if (eager_promotion) {
+	  stp = &generations[evac_gen].steps[0];
+      } else {
+	  failed_to_evac = rtsTrue;
+      }
+  }
+
+  if (stp->hp + size_to_reserve >= stp->hpLim) {
+    gc_alloc_block(stp);
+  }
+
+  for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
+    *to++ = *from++;
+  }
+  
+  dest = stp->hp;
+  stp->hp += size_to_reserve;
+  upd_evacuee(src,(StgClosure *)dest);
+#ifdef PROFILING
+  // We store the size of the just evacuated object in the LDV word so that
+  // the profiler can guess the position of the next object later.
+  // size_to_copy_org is wrong because the closure already occupies size_to_reserve
+  // words.
+  SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
+  // fill the slop
+  if (size_to_reserve - size_to_copy_org > 0)
+    LDV_FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org)); 
+#endif
+  return (StgClosure *)dest;
+}
+
+
+/* -----------------------------------------------------------------------------
+   Evacuate a large object
+
+   This just consists of removing the object from the (doubly-linked)
+   step->large_objects list, and linking it on to the (singly-linked)
+   step->new_large_objects list, from where it will be scavenged later.
+
+   Convention: bd->flags has BF_EVACUATED set for a large object
+   that has been evacuated, or unset otherwise.
+   -------------------------------------------------------------------------- */
+
+
+STATIC_INLINE void
+evacuate_large(StgPtr p)
+{
+  bdescr *bd = Bdescr(p);
+  step *stp;
+
+  // object must be at the beginning of the block (or be a ByteArray)
+  ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
+	 (((W_)p & BLOCK_MASK) == 0));
+
+  // already evacuated? 
+  if (bd->flags & BF_EVACUATED) { 
+    /* Don't forget to set the failed_to_evac flag if we didn't get
+     * the desired destination (see comments in evacuate()).
+     */
+    if (bd->gen_no < evac_gen) {
+      failed_to_evac = rtsTrue;
+      TICK_GC_FAILED_PROMOTION();
+    }
+    return;
+  }
+
+  stp = bd->step;
+  // remove from large_object list 
+  if (bd->u.back) {
+    bd->u.back->link = bd->link;
+  } else { // first object in the list 
+    stp->large_objects = bd->link;
+  }
+  if (bd->link) {
+    bd->link->u.back = bd->u.back;
+  }
+  
+  /* link it on to the evacuated large object list of the destination step
+   */
+  stp = bd->step->to;
+  if (stp->gen_no < evac_gen) {
+      if (eager_promotion) {
+	  stp = &generations[evac_gen].steps[0];
+      } else {
+	  failed_to_evac = rtsTrue;
+      }
+  }
+
+  bd->step = stp;
+  bd->gen_no = stp->gen_no;
+  bd->link = stp->new_large_objects;
+  stp->new_large_objects = bd;
+  bd->flags |= BF_EVACUATED;
+}
+
+/* -----------------------------------------------------------------------------
+   Evacuate
+
+   This is called (eventually) for every live object in the system.
+
+   The caller to evacuate specifies a desired generation in the
+   evac_gen global variable.  The following conditions apply to
+   evacuating an object which resides in generation M when we're
+   collecting up to generation N
+
+   if  M >= evac_gen 
+           if  M > N     do nothing
+	   else          evac to step->to
+
+   if  M < evac_gen      evac to evac_gen, step 0
+
+   if the object is already evacuated, then we check which generation
+   it now resides in.
+
+   if  M >= evac_gen     do nothing
+   if  M <  evac_gen     set failed_to_evac flag to indicate that we
+                         didn't manage to evacuate this object into evac_gen.
+
+
+   OPTIMISATION NOTES:
+
+   evacuate() is the single most important function performance-wise
+   in the GC.  Various things have been tried to speed it up, but as
+   far as I can tell the code generated by gcc 3.2 with -O2 is about
+   as good as it's going to get.  We pass the argument to evacuate()
+   in a register using the 'regparm' attribute (see the prototype for
+   evacuate() near the top of this file).
+
+   Changing evacuate() to take an (StgClosure **) rather than
+   returning the new pointer seems attractive, because we can avoid
+   writing back the pointer when it hasn't changed (eg. for a static
+   object, or an object in a generation > N).  However, I tried it and
+   it doesn't help.  One reason is that the (StgClosure **) pointer
+   gets spilled to the stack inside evacuate(), resulting in far more
+   extra reads/writes than we save.
+   -------------------------------------------------------------------------- */
+
+REGPARM1 StgClosure *
+evacuate(StgClosure *q)
+{
+#if defined(PAR)
+  StgClosure *to;
+#endif
+  bdescr *bd = NULL;
+  step *stp;
+  const StgInfoTable *info;
+
+loop:
+  ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
+
+  if (!HEAP_ALLOCED(q)) {
+
+      if (!major_gc) return q;
+
+      info = get_itbl(q);
+      switch (info->type) {
+
+      case THUNK_STATIC:
+	  if (info->srt_bitmap != 0 && 
+	      *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
+	      *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
+	      static_objects = (StgClosure *)q;
+	  }
+	  return q;
+	  
+      case FUN_STATIC:
+	  if (info->srt_bitmap != 0 && 
+	      *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
+	      *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
+	      static_objects = (StgClosure *)q;
+	  }
+	  return q;
+	  
+      case IND_STATIC:
+	  /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
+	   * on the CAF list, so don't do anything with it here (we'll
+	   * scavenge it later).
+	   */
+	  if (((StgIndStatic *)q)->saved_info == NULL
+	      && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
+	      *IND_STATIC_LINK((StgClosure *)q) = static_objects;
+	      static_objects = (StgClosure *)q;
+	  }
+	  return q;
+	  
+      case CONSTR_STATIC:
+	  if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
+	      *STATIC_LINK(info,(StgClosure *)q) = static_objects;
+	      static_objects = (StgClosure *)q;
+	  }
+	  return q;
+	  
+      case CONSTR_NOCAF_STATIC:
+	  /* no need to put these on the static linked list, they don't need
+	   * to be scavenged.
+	   */
+	  return q;
+	  
+      default:
+	  barf("evacuate(static): strange closure type %d", (int)(info->type));
+      }
+  }
+
+  bd = Bdescr((P_)q);
+
+  if (bd->gen_no > N) {
+      /* Can't evacuate this object, because it's in a generation
+       * older than the ones we're collecting.  Let's hope that it's
+       * in evac_gen or older, or we will have to arrange to track
+       * this pointer using the mutable list.
+       */
+      if (bd->gen_no < evac_gen) {
+	  // nope 
+	  failed_to_evac = rtsTrue;
+	  TICK_GC_FAILED_PROMOTION();
+      }
+      return q;
+  }
+
+  if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
+
+      /* pointer into to-space: just return it.  This normally
+       * shouldn't happen, but alllowing it makes certain things
+       * slightly easier (eg. the mutable list can contain the same
+       * object twice, for example).
+       */
+      if (bd->flags & BF_EVACUATED) {
+	  if (bd->gen_no < evac_gen) {
+	      failed_to_evac = rtsTrue;
+	      TICK_GC_FAILED_PROMOTION();
+	  }
+	  return q;
+      }
+
+      /* evacuate large objects by re-linking them onto a different list.
+       */
+      if (bd->flags & BF_LARGE) {
+	  info = get_itbl(q);
+	  if (info->type == TSO && 
+	      ((StgTSO *)q)->what_next == ThreadRelocated) {
+	      q = (StgClosure *)((StgTSO *)q)->link;
+	      goto loop;
+	  }
+	  evacuate_large((P_)q);
+	  return q;
+      }
+      
+      /* If the object is in a step that we're compacting, then we
+       * need to use an alternative evacuate procedure.
+       */
+      if (bd->flags & BF_COMPACTED) {
+	  if (!is_marked((P_)q,bd)) {
+	      mark((P_)q,bd);
+	      if (mark_stack_full()) {
+		  mark_stack_overflowed = rtsTrue;
+		  reset_mark_stack();
+	      }
+	      push_mark_stack((P_)q);
+	  }
+	  return q;
+      }
+  }
+      
+  stp = bd->step->to;
+
+  info = get_itbl(q);
+  
+  switch (info->type) {
+
+  case MUT_VAR_CLEAN:
+  case MUT_VAR_DIRTY:
+  case MVAR:
+      return copy(q,sizeW_fromITBL(info),stp);
+
+  case CONSTR_0_1:
+  { 
+      StgWord w = (StgWord)q->payload[0];
+      if (q->header.info == Czh_con_info &&
+	  // unsigned, so always true:  (StgChar)w >= MIN_CHARLIKE &&  
+	  (StgChar)w <= MAX_CHARLIKE) {
+	  return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
+      }
+      if (q->header.info == Izh_con_info &&
+	  (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
+	  return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
+      }
+      // else
+      return copy_noscav(q,sizeofW(StgHeader)+1,stp);
+  }
+
+  case FUN_0_1:
+  case FUN_1_0:
+  case CONSTR_1_0:
+    return copy(q,sizeofW(StgHeader)+1,stp);
+
+  case THUNK_1_0:
+  case THUNK_0_1:
+    return copy(q,sizeofW(StgThunk)+1,stp);
+
+  case THUNK_1_1:
+  case THUNK_2_0:
+  case THUNK_0_2:
+#ifdef NO_PROMOTE_THUNKS
+    if (bd->gen_no == 0 && 
+	bd->step->no != 0 &&
+	bd->step->no == generations[bd->gen_no].n_steps-1) {
+      stp = bd->step;
+    }
+#endif
+    return copy(q,sizeofW(StgThunk)+2,stp);
+
+  case FUN_1_1:
+  case FUN_2_0:
+  case CONSTR_1_1:
+  case CONSTR_2_0:
+  case FUN_0_2:
+    return copy(q,sizeofW(StgHeader)+2,stp);
+
+  case CONSTR_0_2:
+    return copy_noscav(q,sizeofW(StgHeader)+2,stp);
+
+  case THUNK:
+    return copy(q,thunk_sizeW_fromITBL(info),stp);
+
+  case FUN:
+  case CONSTR:
+  case IND_PERM:
+  case IND_OLDGEN_PERM:
+  case WEAK:
+  case STABLE_NAME:
+    return copy(q,sizeW_fromITBL(info),stp);
+
+  case BCO:
+      return copy(q,bco_sizeW((StgBCO *)q),stp);
+
+  case CAF_BLACKHOLE:
+  case SE_CAF_BLACKHOLE:
+  case SE_BLACKHOLE:
+  case BLACKHOLE:
+    return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
+
+  case THUNK_SELECTOR:
+    {
+	StgClosure *p;
+	const StgInfoTable *info_ptr;
+
+	if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
+	    return copy(q,THUNK_SELECTOR_sizeW(),stp);
+	}
+
+	// stashed away for LDV profiling, see below
+	info_ptr = q->header.info;
+
+	p = eval_thunk_selector(info->layout.selector_offset,
+				(StgSelector *)q);
+
+	if (p == NULL) {
+	    return copy(q,THUNK_SELECTOR_sizeW(),stp);
+	} else {
+	    StgClosure *val;
+	    // q is still BLACKHOLE'd.
+	    thunk_selector_depth++;
+	    val = evacuate(p);
+	    thunk_selector_depth--;
+
+#ifdef PROFILING
+	    // For the purposes of LDV profiling, we have destroyed
+	    // the original selector thunk.
+	    SET_INFO(q, info_ptr);
+	    LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(q);
+#endif
+
+	    // Update the THUNK_SELECTOR with an indirection to the
+	    // EVACUATED closure now at p.  Why do this rather than
+	    // upd_evacuee(q,p)?  Because we have an invariant that an
+	    // EVACUATED closure always points to an object in the
+	    // same or an older generation (required by the short-cut
+	    // test in the EVACUATED case, below).
+	    SET_INFO(q, &stg_IND_info);
+	    ((StgInd *)q)->indirectee = p;
+
+	    // For the purposes of LDV profiling, we have created an
+	    // indirection.
+	    LDV_RECORD_CREATE(q);
+
+	    return val;
+	}
+    }
+
+  case IND:
+  case IND_OLDGEN:
+    // follow chains of indirections, don't evacuate them 
+    q = ((StgInd*)q)->indirectee;
+    goto loop;
+
+  case RET_BCO:
+  case RET_SMALL:
+  case RET_VEC_SMALL:
+  case RET_BIG:
+  case RET_VEC_BIG:
+  case RET_DYN:
+  case UPDATE_FRAME:
+  case STOP_FRAME:
+  case CATCH_FRAME:
+  case CATCH_STM_FRAME:
+  case CATCH_RETRY_FRAME:
+  case ATOMICALLY_FRAME:
+    // shouldn't see these 
+    barf("evacuate: stack frame at %p\n", q);
+
+  case PAP:
+      return copy(q,pap_sizeW((StgPAP*)q),stp);
+
+  case AP:
+      return copy(q,ap_sizeW((StgAP*)q),stp);
+
+  case AP_STACK:
+      return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
+
+  case EVACUATED:
+    /* Already evacuated, just return the forwarding address.
+     * HOWEVER: if the requested destination generation (evac_gen) is
+     * older than the actual generation (because the object was
+     * already evacuated to a younger generation) then we have to
+     * set the failed_to_evac flag to indicate that we couldn't 
+     * manage to promote the object to the desired generation.
+     */
+    /* 
+     * Optimisation: the check is fairly expensive, but we can often
+     * shortcut it if either the required generation is 0, or the
+     * current object (the EVACUATED) is in a high enough generation.
+     * We know that an EVACUATED always points to an object in the
+     * same or an older generation.  stp is the lowest step that the
+     * current object would be evacuated to, so we only do the full
+     * check if stp is too low.
+     */
+    if (evac_gen > 0 && stp->gen_no < evac_gen) {  // optimisation 
+      StgClosure *p = ((StgEvacuated*)q)->evacuee;
+      if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
+	failed_to_evac = rtsTrue;
+	TICK_GC_FAILED_PROMOTION();
+      }
+    }
+    return ((StgEvacuated*)q)->evacuee;
+
+  case ARR_WORDS:
+      // just copy the block 
+      return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
+
+  case MUT_ARR_PTRS_CLEAN:
+  case MUT_ARR_PTRS_DIRTY:
+  case MUT_ARR_PTRS_FROZEN:
+  case MUT_ARR_PTRS_FROZEN0:
+      // just copy the block 
+      return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
+
+  case TSO:
+    {
+      StgTSO *tso = (StgTSO *)q;
+
+      /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
+       */
+      if (tso->what_next == ThreadRelocated) {
+	q = (StgClosure *)tso->link;
+	goto loop;
+      }
+
+      /* To evacuate a small TSO, we need to relocate the update frame
+       * list it contains.  
+       */
+      {
+	  StgTSO *new_tso;
+	  StgPtr p, q;
+
+	  new_tso = (StgTSO *)copyPart((StgClosure *)tso,
+				       tso_sizeW(tso),
+				       sizeofW(StgTSO), stp);
+	  move_TSO(tso, new_tso);
+	  for (p = tso->sp, q = new_tso->sp;
+	       p < tso->stack+tso->stack_size;) {
+	      *q++ = *p++;
+	  }
+	  
+	  return (StgClosure *)new_tso;
+      }
+    }
+
+#if defined(PAR)
+  case RBH:
+    {
+      //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
+      to = copy(q,BLACKHOLE_sizeW(),stp); 
+      //ToDo: derive size etc from reverted IP
+      //to = copy(q,size,stp);
+      debugTrace(DEBUG_gc, "evacuate: RBH %p (%s) to %p (%s)",
+		 q, info_type(q), to, info_type(to));
+      return to;
+    }
+  
+  case BLOCKED_FETCH:
+    ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOD_SIZE);
+    to = copy(q,sizeofW(StgBlockedFetch),stp);
+    debugTrace(DEBUG_gc, "evacuate: %p (%s) to %p (%s)",
+	       q, info_type(q), to, info_type(to));
+    return to;
+
+# ifdef DIST    
+  case REMOTE_REF:
+# endif
+  case FETCH_ME:
+    ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
+    to = copy(q,sizeofW(StgFetchMe),stp);
+    debugTrace(DEBUG_gc, "evacuate: %p (%s) to %p (%s)",
+	       q, info_type(q), to, info_type(to)));
+    return to;
+
+  case FETCH_ME_BQ:
+    ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
+    to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
+    debugTrace(DEBUG_gc, "evacuate: %p (%s) to %p (%s)",
+	       q, info_type(q), to, info_type(to)));
+    return to;
+#endif
+
+  case TREC_HEADER: 
+    return copy(q,sizeofW(StgTRecHeader),stp);
+
+  case TVAR_WATCH_QUEUE:
+    return copy(q,sizeofW(StgTVarWatchQueue),stp);
+
+  case TVAR:
+    return copy(q,sizeofW(StgTVar),stp);
+    
+  case TREC_CHUNK:
+    return copy(q,sizeofW(StgTRecChunk),stp);
+
+  case ATOMIC_INVARIANT:
+    return copy(q,sizeofW(StgAtomicInvariant),stp);
+
+  case INVARIANT_CHECK_QUEUE:
+    return copy(q,sizeofW(StgInvariantCheckQueue),stp);
+
+  default:
+    barf("evacuate: strange closure type %d", (int)(info->type));
+  }
+
+  barf("evacuate");
+}
+
+/* -----------------------------------------------------------------------------
+   Evaluate a THUNK_SELECTOR if possible.
+
+   returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
+   a closure pointer if we evaluated it and this is the result.  Note
+   that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
+   reducing it to HNF, just that we have eliminated the selection.
+   The result might be another thunk, or even another THUNK_SELECTOR.
+
+   If the return value is non-NULL, the original selector thunk has
+   been BLACKHOLE'd, and should be updated with an indirection or a
+   forwarding pointer.  If the return value is NULL, then the selector
+   thunk is unchanged.
+
+   ***
+   ToDo: the treatment of THUNK_SELECTORS could be improved in the
+   following way (from a suggestion by Ian Lynagh):
+
+   We can have a chain like this:
+
+      sel_0 --> (a,b)
+                 |
+                 |-----> sel_0 --> (a,b)
+                                    |
+                                    |-----> sel_0 --> ...
+
+   and the depth limit means we don't go all the way to the end of the
+   chain, which results in a space leak.  This affects the recursive
+   call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
+   the recursive call to eval_thunk_selector() in
+   eval_thunk_selector().
+
+   We could eliminate the depth bound in this case, in the following
+   way:
+
+      - traverse the chain once to discover the *value* of the 
+        THUNK_SELECTOR.  Mark all THUNK_SELECTORS that we
+        visit on the way as having been visited already (somehow).
+
+      - in a second pass, traverse the chain again updating all
+        THUNK_SEELCTORS that we find on the way with indirections to
+        the value.
+
+      - if we encounter a "marked" THUNK_SELECTOR in a normal 
+        evacuate(), we konw it can't be updated so just evac it.
+
+   Program that illustrates the problem:
+
+	foo [] = ([], [])
+	foo (x:xs) = let (ys, zs) = foo xs
+	             in if x >= 0 then (x:ys, zs) else (ys, x:zs)
+
+	main = bar [1..(100000000::Int)]
+	bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
+
+   -------------------------------------------------------------------------- */
+
+static inline rtsBool
+is_to_space ( StgClosure *p )
+{
+    bdescr *bd;
+
+    bd = Bdescr((StgPtr)p);
+    if (HEAP_ALLOCED(p) &&
+	((bd->flags & BF_EVACUATED) 
+	 || ((bd->flags & BF_COMPACTED) &&
+	     is_marked((P_)p,bd)))) {
+	return rtsTrue;
+    } else {
+	return rtsFalse;
+    }
+}    
+
+static StgClosure *
+eval_thunk_selector( nat field, StgSelector * p )
+{
+    StgInfoTable *info;
+    const StgInfoTable *info_ptr;
+    StgClosure *selectee;
+    
+    selectee = p->selectee;
+
+    // Save the real info pointer (NOTE: not the same as get_itbl()).
+    info_ptr = p->header.info;
+
+    // If the THUNK_SELECTOR is in a generation that we are not
+    // collecting, then bail out early.  We won't be able to save any
+    // space in any case, and updating with an indirection is trickier
+    // in an old gen.
+    if (Bdescr((StgPtr)p)->gen_no > N) {
+	return NULL;
+    }
+
+    // BLACKHOLE the selector thunk, since it is now under evaluation.
+    // This is important to stop us going into an infinite loop if
+    // this selector thunk eventually refers to itself.
+    SET_INFO(p,&stg_BLACKHOLE_info);
+
+selector_loop:
+
+    // We don't want to end up in to-space, because this causes
+    // problems when the GC later tries to evacuate the result of
+    // eval_thunk_selector().  There are various ways this could
+    // happen:
+    //
+    // 1. following an IND_STATIC
+    //
+    // 2. when the old generation is compacted, the mark phase updates
+    //    from-space pointers to be to-space pointers, and we can't
+    //    reliably tell which we're following (eg. from an IND_STATIC).
+    // 
+    // 3. compacting GC again: if we're looking at a constructor in
+    //    the compacted generation, it might point directly to objects
+    //    in to-space.  We must bale out here, otherwise doing the selection
+    //    will result in a to-space pointer being returned.
+    //
+    //  (1) is dealt with using a BF_EVACUATED test on the
+    //  selectee. (2) and (3): we can tell if we're looking at an
+    //  object in the compacted generation that might point to
+    //  to-space objects by testing that (a) it is BF_COMPACTED, (b)
+    //  the compacted generation is being collected, and (c) the
+    //  object is marked.  Only a marked object may have pointers that
+    //  point to to-space objects, because that happens when
+    //  scavenging.
+    //
+    //  The to-space test is now embodied in the in_to_space() inline
+    //  function, as it is re-used below.
+    //
+    if (is_to_space(selectee)) {
+	goto bale_out;
+    }
+
+    info = get_itbl(selectee);
+    switch (info->type) {
+      case CONSTR:
+      case CONSTR_1_0:
+      case CONSTR_0_1:
+      case CONSTR_2_0:
+      case CONSTR_1_1:
+      case CONSTR_0_2:
+      case CONSTR_STATIC:
+      case CONSTR_NOCAF_STATIC:
+	  // check that the size is in range 
+	  ASSERT(field <  (StgWord32)(info->layout.payload.ptrs + 
+				      info->layout.payload.nptrs));
+	  
+	  // Select the right field from the constructor, and check
+	  // that the result isn't in to-space.  It might be in
+	  // to-space if, for example, this constructor contains
+	  // pointers to younger-gen objects (and is on the mut-once
+	  // list).
+	  //
+	  { 
+	      StgClosure *q;
+	      q = selectee->payload[field];
+	      if (is_to_space(q)) {
+		  goto bale_out;
+	      } else {
+		  return q;
+	      }
+	  }
+
+      case IND:
+      case IND_PERM:
+      case IND_OLDGEN:
+      case IND_OLDGEN_PERM:
+      case IND_STATIC:
+	  selectee = ((StgInd *)selectee)->indirectee;
+	  goto selector_loop;
+
+      case EVACUATED:
+	  // We don't follow pointers into to-space; the constructor
+	  // has already been evacuated, so we won't save any space
+	  // leaks by evaluating this selector thunk anyhow.
+	  break;
+
+      case THUNK_SELECTOR:
+      {
+	  StgClosure *val;
+
+	  // check that we don't recurse too much, re-using the
+	  // depth bound also used in evacuate().
+	  if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
+	      break;
+	  }
+	  thunk_selector_depth++;
+
+	  val = eval_thunk_selector(info->layout.selector_offset, 
+				    (StgSelector *)selectee);
+
+	  thunk_selector_depth--;
+
+	  if (val == NULL) { 
+	      break;
+	  } else {
+	      // We evaluated this selector thunk, so update it with
+	      // an indirection.  NOTE: we don't use UPD_IND here,
+	      // because we are guaranteed that p is in a generation
+	      // that we are collecting, and we never want to put the
+	      // indirection on a mutable list.
+#ifdef PROFILING
+	      // For the purposes of LDV profiling, we have destroyed
+	      // the original selector thunk.
+	      SET_INFO(p, info_ptr);
+	      LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
+#endif
+	      ((StgInd *)selectee)->indirectee = val;
+	      SET_INFO(selectee,&stg_IND_info);
+
+	      // For the purposes of LDV profiling, we have created an
+	      // indirection.
+	      LDV_RECORD_CREATE(selectee);
+
+	      selectee = val;
+	      goto selector_loop;
+	  }
+      }
+
+      case AP:
+      case AP_STACK:
+      case THUNK:
+      case THUNK_1_0:
+      case THUNK_0_1:
+      case THUNK_2_0:
+      case THUNK_1_1:
+      case THUNK_0_2:
+      case THUNK_STATIC:
+      case CAF_BLACKHOLE:
+      case SE_CAF_BLACKHOLE:
+      case SE_BLACKHOLE:
+      case BLACKHOLE:
+#if defined(PAR)
+      case RBH:
+      case BLOCKED_FETCH:
+# ifdef DIST    
+      case REMOTE_REF:
+# endif
+      case FETCH_ME:
+      case FETCH_ME_BQ:
+#endif
+	  // not evaluated yet 
+	  break;
+    
+      default:
+	barf("eval_thunk_selector: strange selectee %d",
+	     (int)(info->type));
+    }
+
+bale_out:
+    // We didn't manage to evaluate this thunk; restore the old info pointer
+    SET_INFO(p, info_ptr);
+    return NULL;
+}
+
+/* -----------------------------------------------------------------------------
+   move_TSO is called to update the TSO structure after it has been
+   moved from one place to another.
+   -------------------------------------------------------------------------- */
+
+void
+move_TSO (StgTSO *src, StgTSO *dest)
+{
+    ptrdiff_t diff;
+
+    // relocate the stack pointer... 
+    diff = (StgPtr)dest - (StgPtr)src; // In *words* 
+    dest->sp = (StgPtr)dest->sp + diff;
+}
+
diff --git a/rts/sm/Evac.h b/rts/sm/Evac.h
new file mode 100644
index 0000000000..c89e4d9a7d
--- /dev/null
+++ b/rts/sm/Evac.h
@@ -0,0 +1,18 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Generational garbage collector: evacuation functions
+ *
+ * ---------------------------------------------------------------------------*/
+
+// Use a register argument for evacuate, if available.
+#if __GNUC__ >= 2
+#define REGPARM1 __attribute__((regparm(1)))
+#else
+#define REGPARM1
+#endif
+
+REGPARM1 StgClosure * evacuate (StgClosure *q);
+
+extern lnat thunk_selector_depth;
diff --git a/rts/sm/GC.c b/rts/sm/GC.c
new file mode 100644
index 0000000000..c181940ccf
--- /dev/null
+++ b/rts/sm/GC.c
@@ -0,0 +1,1275 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2003
+ *
+ * Generational garbage collector
+ *
+ * ---------------------------------------------------------------------------*/
+
+#include "PosixSource.h"
+#include "Rts.h"
+#include "RtsFlags.h"
+#include "RtsUtils.h"
+#include "Apply.h"
+#include "OSThreads.h"
+#include "Storage.h"
+#include "Stable.h"
+#include "LdvProfile.h"
+#include "Updates.h"
+#include "Stats.h"
+#include "Schedule.h"
+#include "Sanity.h"
+#include "BlockAlloc.h"
+#include "MBlock.h"
+#include "ProfHeap.h"
+#include "SchedAPI.h"
+#include "Weak.h"
+#include "Prelude.h"
+#include "ParTicky.h"		// ToDo: move into Rts.h
+#include "RtsSignals.h"
+#include "STM.h"
+#if defined(GRAN) || defined(PAR)
+# include "GranSimRts.h"
+# include "ParallelRts.h"
+# include "FetchMe.h"
+# if defined(DEBUG)
+#  include "Printer.h"
+#  include "ParallelDebug.h"
+# endif
+#endif
+#include "HsFFI.h"
+#include "Linker.h"
+#if defined(RTS_GTK_FRONTPANEL)
+#include "FrontPanel.h"
+#endif
+#include "Trace.h"
+#include "RetainerProfile.h"
+#include "RaiseAsync.h"
+
+#include "GC.h"
+#include "Compact.h"
+#include "Evac.h"
+#include "Scav.h"
+#include "GCUtils.h"
+#include "MarkWeak.h"
+
+#include <string.h> // for memset()
+
+/* STATIC OBJECT LIST.
+ *
+ * During GC:
+ * We maintain a linked list of static objects that are still live.
+ * The requirements for this list are:
+ *
+ *  - we need to scan the list while adding to it, in order to
+ *    scavenge all the static objects (in the same way that
+ *    breadth-first scavenging works for dynamic objects).
+ *
+ *  - we need to be able to tell whether an object is already on
+ *    the list, to break loops.
+ *
+ * Each static object has a "static link field", which we use for
+ * linking objects on to the list.  We use a stack-type list, consing
+ * objects on the front as they are added (this means that the
+ * scavenge phase is depth-first, not breadth-first, but that
+ * shouldn't matter).  
+ *
+ * A separate list is kept for objects that have been scavenged
+ * already - this is so that we can zero all the marks afterwards.
+ *
+ * An object is on the list if its static link field is non-zero; this
+ * means that we have to mark the end of the list with '1', not NULL.  
+ *
+ * Extra notes for generational GC:
+ *
+ * Each generation has a static object list associated with it.  When
+ * collecting generations up to N, we treat the static object lists
+ * from generations > N as roots.
+ *
+ * We build up a static object list while collecting generations 0..N,
+ * which is then appended to the static object list of generation N+1.
+ */
+StgClosure* static_objects;      // live static objects
+StgClosure* scavenged_static_objects;   // static objects scavenged so far
+
+/* N is the oldest generation being collected, where the generations
+ * are numbered starting at 0.  A major GC (indicated by the major_gc
+ * flag) is when we're collecting all generations.  We only attempt to
+ * deal with static objects and GC CAFs when doing a major GC.
+ */
+nat N;
+rtsBool major_gc;
+
+/* Youngest generation that objects should be evacuated to in
+ * evacuate().  (Logically an argument to evacuate, but it's static
+ * a lot of the time so we optimise it into a global variable).
+ */
+nat evac_gen;
+
+/* Whether to do eager promotion or not.
+ */
+rtsBool eager_promotion;
+
+/* Flag indicating failure to evacuate an object to the desired
+ * generation.
+ */
+rtsBool failed_to_evac;
+
+/* Saved nursery (used for 2-space collector only)
+ */
+static bdescr *saved_nursery;
+static nat saved_n_blocks;
+  
+/* Data used for allocation area sizing.
+ */
+lnat new_blocks;		 // blocks allocated during this GC 
+lnat new_scavd_blocks;	 // ditto, but depth-first blocks
+static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC 
+
+/* Mut-list stats */
+#ifdef DEBUG
+nat mutlist_MUTVARS,
+    mutlist_MUTARRS,
+    mutlist_OTHERS;
+#endif
+
+/* -----------------------------------------------------------------------------
+   Static function declarations
+   -------------------------------------------------------------------------- */
+
+static void         mark_root               ( StgClosure **root );
+
+static void         zero_static_object_list ( StgClosure* first_static );
+
+#if 0 && defined(DEBUG)
+static void         gcCAFs                  ( void );
+#endif
+
+/* -----------------------------------------------------------------------------
+   inline functions etc. for dealing with the mark bitmap & stack.
+   -------------------------------------------------------------------------- */
+
+#define MARK_STACK_BLOCKS 4
+
+bdescr *mark_stack_bdescr;
+StgPtr *mark_stack;
+StgPtr *mark_sp;
+StgPtr *mark_splim;
+
+// Flag and pointers used for falling back to a linear scan when the
+// mark stack overflows.
+rtsBool mark_stack_overflowed;
+bdescr *oldgen_scan_bd;
+StgPtr  oldgen_scan;
+
+/* -----------------------------------------------------------------------------
+   GarbageCollect
+
+   Rough outline of the algorithm: for garbage collecting generation N
+   (and all younger generations):
+
+     - follow all pointers in the root set.  the root set includes all 
+       mutable objects in all generations (mutable_list).
+
+     - for each pointer, evacuate the object it points to into either
+
+       + to-space of the step given by step->to, which is the next
+         highest step in this generation or the first step in the next
+         generation if this is the last step.
+
+       + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
+         When we evacuate an object we attempt to evacuate
+         everything it points to into the same generation - this is
+         achieved by setting evac_gen to the desired generation.  If
+         we can't do this, then an entry in the mut list has to
+         be made for the cross-generation pointer.
+
+       + if the object is already in a generation > N, then leave
+         it alone.
+
+     - repeatedly scavenge to-space from each step in each generation
+       being collected until no more objects can be evacuated.
+      
+     - free from-space in each step, and set from-space = to-space.
+
+   Locks held: all capabilities are held throughout GarbageCollect().
+
+   -------------------------------------------------------------------------- */
+
+void
+GarbageCollect ( rtsBool force_major_gc )
+{
+  bdescr *bd;
+  step *stp;
+  lnat live, allocated, copied = 0, scavd_copied = 0;
+  lnat oldgen_saved_blocks = 0;
+  nat g, s, i;
+
+  ACQUIRE_SM_LOCK;
+
+#ifdef PROFILING
+  CostCentreStack *prev_CCS;
+#endif
+
+  debugTrace(DEBUG_gc, "starting GC");
+
+#if defined(RTS_USER_SIGNALS)
+  // block signals
+  blockUserSignals();
+#endif
+
+  // tell the STM to discard any cached closures its hoping to re-use
+  stmPreGCHook();
+
+  // tell the stats department that we've started a GC 
+  stat_startGC();
+
+#ifdef DEBUG
+  // check for memory leaks if DEBUG is on 
+  memInventory();
+#endif
+
+#ifdef DEBUG
+  mutlist_MUTVARS = 0;
+  mutlist_MUTARRS = 0;
+  mutlist_OTHERS = 0;
+#endif
+
+  // Init stats and print par specific (timing) info 
+  PAR_TICKY_PAR_START();
+
+  // attribute any costs to CCS_GC 
+#ifdef PROFILING
+  prev_CCS = CCCS;
+  CCCS = CCS_GC;
+#endif
+
+  /* Approximate how much we allocated.  
+   * Todo: only when generating stats? 
+   */
+  allocated = calcAllocated();
+
+  /* Figure out which generation to collect
+   */
+  if (force_major_gc) {
+    N = RtsFlags.GcFlags.generations - 1;
+    major_gc = rtsTrue;
+  } else {
+    N = 0;
+    for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
+      if (generations[g].steps[0].n_blocks +
+	  generations[g].steps[0].n_large_blocks
+	  >= generations[g].max_blocks) {
+        N = g;
+      }
+    }
+    major_gc = (N == RtsFlags.GcFlags.generations-1);
+  }
+
+#ifdef RTS_GTK_FRONTPANEL
+  if (RtsFlags.GcFlags.frontpanel) {
+      updateFrontPanelBeforeGC(N);
+  }
+#endif
+
+  // check stack sanity *before* GC (ToDo: check all threads) 
+#if defined(GRAN)
+  // ToDo!: check sanity  IF_DEBUG(sanity, checkTSOsSanity());
+#endif
+  IF_DEBUG(sanity, checkFreeListSanity());
+
+  /* Initialise the static object lists
+   */
+  static_objects = END_OF_STATIC_LIST;
+  scavenged_static_objects = END_OF_STATIC_LIST;
+
+  /* Save the nursery if we're doing a two-space collection.
+   * g0s0->blocks will be used for to-space, so we need to get the
+   * nursery out of the way.
+   */
+  if (RtsFlags.GcFlags.generations == 1) {
+      saved_nursery = g0s0->blocks;
+      saved_n_blocks = g0s0->n_blocks;
+      g0s0->blocks = NULL;
+      g0s0->n_blocks = 0;
+  }
+
+  /* Keep a count of how many new blocks we allocated during this GC
+   * (used for resizing the allocation area, later).
+   */
+  new_blocks = 0;
+  new_scavd_blocks = 0;
+
+  // Initialise to-space in all the generations/steps that we're
+  // collecting.
+  //
+  for (g = 0; g <= N; g++) {
+
+    // throw away the mutable list.  Invariant: the mutable list
+    // always has at least one block; this means we can avoid a check for
+    // NULL in recordMutable().
+    if (g != 0) {
+	freeChain(generations[g].mut_list);
+	generations[g].mut_list = allocBlock();
+	for (i = 0; i < n_capabilities; i++) {
+	    freeChain(capabilities[i].mut_lists[g]);
+	    capabilities[i].mut_lists[g] = allocBlock();
+	}
+    }
+
+    for (s = 0; s < generations[g].n_steps; s++) {
+
+      // generation 0, step 0 doesn't need to-space 
+      if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) { 
+	continue; 
+      }
+
+      stp = &generations[g].steps[s];
+      ASSERT(stp->gen_no == g);
+
+      // start a new to-space for this step.
+      stp->old_blocks   = stp->blocks;
+      stp->n_old_blocks = stp->n_blocks;
+
+      // allocate the first to-space block; extra blocks will be
+      // chained on as necessary.
+      stp->hp_bd     = NULL;
+      bd = gc_alloc_block(stp);
+      stp->blocks      = bd;
+      stp->n_blocks    = 1;
+      stp->scan        = bd->start;
+      stp->scan_bd     = bd;
+
+      // allocate a block for "already scavenged" objects.  This goes
+      // on the front of the stp->blocks list, so it won't be
+      // traversed by the scavenging sweep.
+      gc_alloc_scavd_block(stp);
+
+      // initialise the large object queues.
+      stp->new_large_objects = NULL;
+      stp->scavenged_large_objects = NULL;
+      stp->n_scavenged_large_blocks = 0;
+
+      // mark the large objects as not evacuated yet 
+      for (bd = stp->large_objects; bd; bd = bd->link) {
+	bd->flags &= ~BF_EVACUATED;
+      }
+
+      // for a compacted step, we need to allocate the bitmap
+      if (stp->is_compacted) {
+	  nat bitmap_size; // in bytes
+	  bdescr *bitmap_bdescr;
+	  StgWord *bitmap;
+
+	  bitmap_size = stp->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
+
+	  if (bitmap_size > 0) {
+	      bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size) 
+					 / BLOCK_SIZE);
+	      stp->bitmap = bitmap_bdescr;
+	      bitmap = bitmap_bdescr->start;
+	      
+	      debugTrace(DEBUG_gc, "bitmap_size: %d, bitmap: %p",
+			 bitmap_size, bitmap);
+	      
+	      // don't forget to fill it with zeros!
+	      memset(bitmap, 0, bitmap_size);
+	      
+	      // For each block in this step, point to its bitmap from the
+	      // block descriptor.
+	      for (bd=stp->old_blocks; bd != NULL; bd = bd->link) {
+		  bd->u.bitmap = bitmap;
+		  bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
+
+		  // Also at this point we set the BF_COMPACTED flag
+		  // for this block.  The invariant is that
+		  // BF_COMPACTED is always unset, except during GC
+		  // when it is set on those blocks which will be
+		  // compacted.
+		  bd->flags |= BF_COMPACTED;
+	      }
+	  }
+      }
+    }
+  }
+
+  /* make sure the older generations have at least one block to
+   * allocate into (this makes things easier for copy(), see below).
+   */
+  for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
+    for (s = 0; s < generations[g].n_steps; s++) {
+      stp = &generations[g].steps[s];
+      if (stp->hp_bd == NULL) {
+	  ASSERT(stp->blocks == NULL);
+	  bd = gc_alloc_block(stp);
+	  stp->blocks = bd;
+	  stp->n_blocks = 1;
+      }
+      if (stp->scavd_hp == NULL) {
+	  gc_alloc_scavd_block(stp);
+	  stp->n_blocks++;
+      }
+      /* Set the scan pointer for older generations: remember we
+       * still have to scavenge objects that have been promoted. */
+      stp->scan = stp->hp;
+      stp->scan_bd = stp->hp_bd;
+      stp->new_large_objects = NULL;
+      stp->scavenged_large_objects = NULL;
+      stp->n_scavenged_large_blocks = 0;
+    }
+
+    /* Move the private mutable lists from each capability onto the
+     * main mutable list for the generation.
+     */
+    for (i = 0; i < n_capabilities; i++) {
+	for (bd = capabilities[i].mut_lists[g]; 
+	     bd->link != NULL; bd = bd->link) {
+	    /* nothing */
+	}
+	bd->link = generations[g].mut_list;
+	generations[g].mut_list = capabilities[i].mut_lists[g];
+	capabilities[i].mut_lists[g] = allocBlock();
+    }
+  }
+
+  /* Allocate a mark stack if we're doing a major collection.
+   */
+  if (major_gc) {
+      mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
+      mark_stack = (StgPtr *)mark_stack_bdescr->start;
+      mark_sp    = mark_stack;
+      mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
+  } else {
+      mark_stack_bdescr = NULL;
+  }
+
+  eager_promotion = rtsTrue; // for now
+
+  /* -----------------------------------------------------------------------
+   * follow all the roots that we know about:
+   *   - mutable lists from each generation > N
+   * we want to *scavenge* these roots, not evacuate them: they're not
+   * going to move in this GC.
+   * Also: do them in reverse generation order.  This is because we
+   * often want to promote objects that are pointed to by older
+   * generations early, so we don't have to repeatedly copy them.
+   * Doing the generations in reverse order ensures that we don't end
+   * up in the situation where we want to evac an object to gen 3 and
+   * it has already been evaced to gen 2.
+   */
+  { 
+    int st;
+    for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
+      generations[g].saved_mut_list = generations[g].mut_list;
+      generations[g].mut_list = allocBlock(); 
+        // mut_list always has at least one block.
+    }
+
+    for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
+      IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
+      scavenge_mutable_list(&generations[g]);
+      evac_gen = g;
+      for (st = generations[g].n_steps-1; st >= 0; st--) {
+	scavenge(&generations[g].steps[st]);
+      }
+    }
+  }
+
+  /* follow roots from the CAF list (used by GHCi)
+   */
+  evac_gen = 0;
+  markCAFs(mark_root);
+
+  /* follow all the roots that the application knows about.
+   */
+  evac_gen = 0;
+  GetRoots(mark_root);
+
+#if defined(PAR)
+  /* And don't forget to mark the TSO if we got here direct from
+   * Haskell! */
+  /* Not needed in a seq version?
+  if (CurrentTSO) {
+    CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
+  }
+  */
+
+  // Mark the entries in the GALA table of the parallel system 
+  markLocalGAs(major_gc);
+  // Mark all entries on the list of pending fetches 
+  markPendingFetches(major_gc);
+#endif
+
+  /* Mark the weak pointer list, and prepare to detect dead weak
+   * pointers.
+   */
+  markWeakPtrList();
+  initWeakForGC();
+
+  /* Mark the stable pointer table.
+   */
+  markStablePtrTable(mark_root);
+
+  /* Mark the root pointer table.
+   */
+  markRootPtrTable(mark_root);
+
+  /* -------------------------------------------------------------------------
+   * Repeatedly scavenge all the areas we know about until there's no
+   * more scavenging to be done.
+   */
+  { 
+    rtsBool flag;
+  loop:
+    flag = rtsFalse;
+
+    // scavenge static objects 
+    if (major_gc && static_objects != END_OF_STATIC_LIST) {
+	IF_DEBUG(sanity, checkStaticObjects(static_objects));
+	scavenge_static();
+    }
+
+    /* When scavenging the older generations:  Objects may have been
+     * evacuated from generations <= N into older generations, and we
+     * need to scavenge these objects.  We're going to try to ensure that
+     * any evacuations that occur move the objects into at least the
+     * same generation as the object being scavenged, otherwise we
+     * have to create new entries on the mutable list for the older
+     * generation.
+     */
+
+    // scavenge each step in generations 0..maxgen 
+    { 
+      long gen;
+      int st; 
+
+    loop2:
+      // scavenge objects in compacted generation
+      if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
+	  (mark_stack_bdescr != NULL && !mark_stack_empty())) {
+	  scavenge_mark_stack();
+	  flag = rtsTrue;
+      }
+
+      for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
+	for (st = generations[gen].n_steps; --st >= 0; ) {
+	  if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) { 
+	    continue; 
+	  }
+	  stp = &generations[gen].steps[st];
+	  evac_gen = gen;
+	  if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
+	    scavenge(stp);
+	    flag = rtsTrue;
+	    goto loop2;
+	  }
+	  if (stp->new_large_objects != NULL) {
+	    scavenge_large(stp);
+	    flag = rtsTrue;
+	    goto loop2;
+	  }
+	}
+      }
+    }
+
+    // if any blackholes are alive, make the threads that wait on
+    // them alive too.
+    if (traverseBlackholeQueue())
+	flag = rtsTrue;
+
+    if (flag) { goto loop; }
+
+    // must be last...  invariant is that everything is fully
+    // scavenged at this point.
+    if (traverseWeakPtrList()) { // returns rtsTrue if evaced something 
+      goto loop;
+    }
+  }
+
+  /* Update the pointers from the task list - these are
+   * treated as weak pointers because we want to allow a main thread
+   * to get a BlockedOnDeadMVar exception in the same way as any other
+   * thread.  Note that the threads should all have been retained by
+   * GC by virtue of being on the all_threads list, we're just
+   * updating pointers here.
+   */
+  {
+      Task *task;
+      StgTSO *tso;
+      for (task = all_tasks; task != NULL; task = task->all_link) {
+	  if (!task->stopped && task->tso) {
+	      ASSERT(task->tso->bound == task);
+	      tso = (StgTSO *) isAlive((StgClosure *)task->tso);
+	      if (tso == NULL) {
+		  barf("task %p: main thread %d has been GC'd", 
+#ifdef THREADED_RTS
+		       (void *)task->id, 
+#else
+		       (void *)task,
+#endif
+		       task->tso->id);
+	      }
+	      task->tso = tso;
+	  }
+      }
+  }
+
+#if defined(PAR)
+  // Reconstruct the Global Address tables used in GUM 
+  rebuildGAtables(major_gc);
+  IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
+#endif
+
+  // Now see which stable names are still alive.
+  gcStablePtrTable();
+
+  // Tidy the end of the to-space chains 
+  for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
+      for (s = 0; s < generations[g].n_steps; s++) {
+	  stp = &generations[g].steps[s];
+	  if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
+	      ASSERT(Bdescr(stp->hp) == stp->hp_bd);
+	      stp->hp_bd->free = stp->hp;
+	      Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
+	  }
+      }
+  }
+
+#ifdef PROFILING
+  // We call processHeapClosureForDead() on every closure destroyed during
+  // the current garbage collection, so we invoke LdvCensusForDead().
+  if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
+      || RtsFlags.ProfFlags.bioSelector != NULL)
+    LdvCensusForDead(N);
+#endif
+
+  // NO MORE EVACUATION AFTER THIS POINT!
+  // Finally: compaction of the oldest generation.
+  if (major_gc && oldest_gen->steps[0].is_compacted) {
+      // save number of blocks for stats
+      oldgen_saved_blocks = oldest_gen->steps[0].n_old_blocks;
+      compact();
+  }
+
+  IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
+
+  /* run through all the generations/steps and tidy up 
+   */
+  copied = new_blocks * BLOCK_SIZE_W;
+  scavd_copied =  new_scavd_blocks * BLOCK_SIZE_W;
+  for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
+
+    if (g <= N) {
+      generations[g].collections++; // for stats 
+    }
+
+    // Count the mutable list as bytes "copied" for the purposes of
+    // stats.  Every mutable list is copied during every GC.
+    if (g > 0) {
+	nat mut_list_size = 0;
+	for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
+	    mut_list_size += bd->free - bd->start;
+	}
+	copied +=  mut_list_size;
+
+	debugTrace(DEBUG_gc,
+		   "mut_list_size: %lu (%d vars, %d arrays, %d others)",
+		   (unsigned long)(mut_list_size * sizeof(W_)),
+		   mutlist_MUTVARS, mutlist_MUTARRS, mutlist_OTHERS);
+    }
+
+    for (s = 0; s < generations[g].n_steps; s++) {
+      bdescr *next;
+      stp = &generations[g].steps[s];
+
+      if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
+	// stats information: how much we copied 
+	if (g <= N) {
+	  copied -= stp->hp_bd->start + BLOCK_SIZE_W -
+	    stp->hp_bd->free;
+	  scavd_copied -= (P_)(BLOCK_ROUND_UP(stp->scavd_hp)) - stp->scavd_hp;
+	}
+      }
+
+      // for generations we collected... 
+      if (g <= N) {
+
+	/* free old memory and shift to-space into from-space for all
+	 * the collected steps (except the allocation area).  These
+	 * freed blocks will probaby be quickly recycled.
+	 */
+	if (!(g == 0 && s == 0)) {
+	    if (stp->is_compacted) {
+		// for a compacted step, just shift the new to-space
+		// onto the front of the now-compacted existing blocks.
+		for (bd = stp->blocks; bd != NULL; bd = bd->link) {
+		    bd->flags &= ~BF_EVACUATED;  // now from-space 
+		}
+		// tack the new blocks on the end of the existing blocks
+		if (stp->old_blocks != NULL) {
+		    for (bd = stp->old_blocks; bd != NULL; bd = next) {
+			// NB. this step might not be compacted next
+			// time, so reset the BF_COMPACTED flags.
+			// They are set before GC if we're going to
+			// compact.  (search for BF_COMPACTED above).
+			bd->flags &= ~BF_COMPACTED;
+			next = bd->link;
+			if (next == NULL) {
+			    bd->link = stp->blocks;
+			}
+		    }
+		    stp->blocks = stp->old_blocks;
+		}
+		// add the new blocks to the block tally
+		stp->n_blocks += stp->n_old_blocks;
+		ASSERT(countBlocks(stp->blocks) == stp->n_blocks);
+	    } else {
+		freeChain(stp->old_blocks);
+		for (bd = stp->blocks; bd != NULL; bd = bd->link) {
+		    bd->flags &= ~BF_EVACUATED;	 // now from-space 
+		}
+	    }
+	    stp->old_blocks = NULL;
+	    stp->n_old_blocks = 0;
+	}
+
+	/* LARGE OBJECTS.  The current live large objects are chained on
+	 * scavenged_large, having been moved during garbage
+	 * collection from large_objects.  Any objects left on
+	 * large_objects list are therefore dead, so we free them here.
+	 */
+	for (bd = stp->large_objects; bd != NULL; bd = next) {
+	  next = bd->link;
+	  freeGroup(bd);
+	  bd = next;
+	}
+
+	// update the count of blocks used by large objects
+	for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
+	  bd->flags &= ~BF_EVACUATED;
+	}
+	stp->large_objects  = stp->scavenged_large_objects;
+	stp->n_large_blocks = stp->n_scavenged_large_blocks;
+
+      } else {
+	// for older generations... 
+	
+	/* For older generations, we need to append the
+	 * scavenged_large_object list (i.e. large objects that have been
+	 * promoted during this GC) to the large_object list for that step.
+	 */
+	for (bd = stp->scavenged_large_objects; bd; bd = next) {
+	  next = bd->link;
+	  bd->flags &= ~BF_EVACUATED;
+	  dbl_link_onto(bd, &stp->large_objects);
+	}
+
+	// add the new blocks we promoted during this GC 
+	stp->n_large_blocks += stp->n_scavenged_large_blocks;
+      }
+    }
+  }
+
+  /* Reset the sizes of the older generations when we do a major
+   * collection.
+   *
+   * CURRENT STRATEGY: make all generations except zero the same size.
+   * We have to stay within the maximum heap size, and leave a certain
+   * percentage of the maximum heap size available to allocate into.
+   */
+  if (major_gc && RtsFlags.GcFlags.generations > 1) {
+      nat live, size, min_alloc;
+      nat max  = RtsFlags.GcFlags.maxHeapSize;
+      nat gens = RtsFlags.GcFlags.generations;
+
+      // live in the oldest generations
+      live = oldest_gen->steps[0].n_blocks +
+	     oldest_gen->steps[0].n_large_blocks;
+
+      // default max size for all generations except zero
+      size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
+		     RtsFlags.GcFlags.minOldGenSize);
+
+      // minimum size for generation zero
+      min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
+			  RtsFlags.GcFlags.minAllocAreaSize);
+
+      // Auto-enable compaction when the residency reaches a
+      // certain percentage of the maximum heap size (default: 30%).
+      if (RtsFlags.GcFlags.generations > 1 &&
+	  (RtsFlags.GcFlags.compact ||
+	   (max > 0 &&
+	    oldest_gen->steps[0].n_blocks > 
+	    (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
+	  oldest_gen->steps[0].is_compacted = 1;
+//	  debugBelch("compaction: on\n", live);
+      } else {
+	  oldest_gen->steps[0].is_compacted = 0;
+//	  debugBelch("compaction: off\n", live);
+      }
+
+      // if we're going to go over the maximum heap size, reduce the
+      // size of the generations accordingly.  The calculation is
+      // different if compaction is turned on, because we don't need
+      // to double the space required to collect the old generation.
+      if (max != 0) {
+
+	  // this test is necessary to ensure that the calculations
+	  // below don't have any negative results - we're working
+	  // with unsigned values here.
+	  if (max < min_alloc) {
+	      heapOverflow();
+	  }
+
+	  if (oldest_gen->steps[0].is_compacted) {
+	      if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
+		  size = (max - min_alloc) / ((gens - 1) * 2 - 1);
+	      }
+	  } else {
+	      if ( (size * (gens - 1) * 2) + min_alloc > max ) {
+		  size = (max - min_alloc) / ((gens - 1) * 2);
+	      }
+	  }
+
+	  if (size < live) {
+	      heapOverflow();
+	  }
+      }
+
+#if 0
+      debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
+	      min_alloc, size, max);
+#endif
+
+      for (g = 0; g < gens; g++) {
+	  generations[g].max_blocks = size;
+      }
+  }
+
+  // Guess the amount of live data for stats.
+  live = calcLive();
+
+  /* Free the small objects allocated via allocate(), since this will
+   * all have been copied into G0S1 now.  
+   */
+  if (small_alloc_list != NULL) {
+    freeChain(small_alloc_list);
+  }
+  small_alloc_list = NULL;
+  alloc_blocks = 0;
+  alloc_Hp = NULL;
+  alloc_HpLim = NULL;
+  alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
+
+  // Start a new pinned_object_block
+  pinned_object_block = NULL;
+
+  /* Free the mark stack.
+   */
+  if (mark_stack_bdescr != NULL) {
+      freeGroup(mark_stack_bdescr);
+  }
+
+  /* Free any bitmaps.
+   */
+  for (g = 0; g <= N; g++) {
+      for (s = 0; s < generations[g].n_steps; s++) {
+	  stp = &generations[g].steps[s];
+	  if (stp->bitmap != NULL) {
+	      freeGroup(stp->bitmap);
+	      stp->bitmap = NULL;
+	  }
+      }
+  }
+
+  /* Two-space collector:
+   * Free the old to-space, and estimate the amount of live data.
+   */
+  if (RtsFlags.GcFlags.generations == 1) {
+    nat blocks;
+    
+    if (g0s0->old_blocks != NULL) {
+      freeChain(g0s0->old_blocks);
+    }
+    for (bd = g0s0->blocks; bd != NULL; bd = bd->link) {
+      bd->flags = 0;	// now from-space 
+    }
+    g0s0->old_blocks = g0s0->blocks;
+    g0s0->n_old_blocks = g0s0->n_blocks;
+    g0s0->blocks = saved_nursery;
+    g0s0->n_blocks = saved_n_blocks;
+
+    /* For a two-space collector, we need to resize the nursery. */
+    
+    /* set up a new nursery.  Allocate a nursery size based on a
+     * function of the amount of live data (by default a factor of 2)
+     * Use the blocks from the old nursery if possible, freeing up any
+     * left over blocks.
+     *
+     * If we get near the maximum heap size, then adjust our nursery
+     * size accordingly.  If the nursery is the same size as the live
+     * data (L), then we need 3L bytes.  We can reduce the size of the
+     * nursery to bring the required memory down near 2L bytes.
+     * 
+     * A normal 2-space collector would need 4L bytes to give the same
+     * performance we get from 3L bytes, reducing to the same
+     * performance at 2L bytes.
+     */
+    blocks = g0s0->n_old_blocks;
+
+    if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
+	 blocks * RtsFlags.GcFlags.oldGenFactor * 2 > 
+	   RtsFlags.GcFlags.maxHeapSize ) {
+      long adjusted_blocks;  // signed on purpose 
+      int pc_free; 
+      
+      adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
+
+      debugTrace(DEBUG_gc, "near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", 
+		 RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks);
+
+      pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
+      if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
+	heapOverflow();
+      }
+      blocks = adjusted_blocks;
+      
+    } else {
+      blocks *= RtsFlags.GcFlags.oldGenFactor;
+      if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
+	blocks = RtsFlags.GcFlags.minAllocAreaSize;
+      }
+    }
+    resizeNurseries(blocks);
+    
+  } else {
+    /* Generational collector:
+     * If the user has given us a suggested heap size, adjust our
+     * allocation area to make best use of the memory available.
+     */
+
+    if (RtsFlags.GcFlags.heapSizeSuggestion) {
+      long blocks;
+      nat needed = calcNeeded(); 	// approx blocks needed at next GC 
+
+      /* Guess how much will be live in generation 0 step 0 next time.
+       * A good approximation is obtained by finding the
+       * percentage of g0s0 that was live at the last minor GC.
+       */
+      if (N == 0) {
+	g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
+      }
+
+      /* Estimate a size for the allocation area based on the
+       * information available.  We might end up going slightly under
+       * or over the suggested heap size, but we should be pretty
+       * close on average.
+       *
+       * Formula:            suggested - needed
+       *                ----------------------------
+       *                    1 + g0s0_pcnt_kept/100
+       *
+       * where 'needed' is the amount of memory needed at the next
+       * collection for collecting all steps except g0s0.
+       */
+      blocks = 
+	(((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
+	(100 + (long)g0s0_pcnt_kept);
+      
+      if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
+	blocks = RtsFlags.GcFlags.minAllocAreaSize;
+      }
+      
+      resizeNurseries((nat)blocks);
+
+    } else {
+      // we might have added extra large blocks to the nursery, so
+      // resize back to minAllocAreaSize again.
+      resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
+    }
+  }
+
+ // mark the garbage collected CAFs as dead 
+#if 0 && defined(DEBUG) // doesn't work at the moment 
+  if (major_gc) { gcCAFs(); }
+#endif
+  
+#ifdef PROFILING
+  // resetStaticObjectForRetainerProfiling() must be called before
+  // zeroing below.
+  resetStaticObjectForRetainerProfiling();
+#endif
+
+  // zero the scavenged static object list 
+  if (major_gc) {
+    zero_static_object_list(scavenged_static_objects);
+  }
+
+  // Reset the nursery
+  resetNurseries();
+
+  // start any pending finalizers 
+  RELEASE_SM_LOCK;
+  scheduleFinalizers(last_free_capability, old_weak_ptr_list);
+  ACQUIRE_SM_LOCK;
+  
+  // send exceptions to any threads which were about to die 
+  RELEASE_SM_LOCK;
+  resurrectThreads(resurrected_threads);
+  ACQUIRE_SM_LOCK;
+
+  // Update the stable pointer hash table.
+  updateStablePtrTable(major_gc);
+
+  // check sanity after GC 
+  IF_DEBUG(sanity, checkSanity());
+
+  // extra GC trace info 
+  IF_DEBUG(gc, statDescribeGens());
+
+#ifdef DEBUG
+  // symbol-table based profiling 
+  /*  heapCensus(to_blocks); */ /* ToDo */
+#endif
+
+  // restore enclosing cost centre 
+#ifdef PROFILING
+  CCCS = prev_CCS;
+#endif
+
+#ifdef DEBUG
+  // check for memory leaks if DEBUG is on 
+  memInventory();
+#endif
+
+#ifdef RTS_GTK_FRONTPANEL
+  if (RtsFlags.GcFlags.frontpanel) {
+      updateFrontPanelAfterGC( N, live );
+  }
+#endif
+
+  // ok, GC over: tell the stats department what happened. 
+  stat_endGC(allocated, live, copied, scavd_copied, N);
+
+#if defined(RTS_USER_SIGNALS)
+  // unblock signals again
+  unblockUserSignals();
+#endif
+
+  RELEASE_SM_LOCK;
+
+  //PAR_TICKY_TP();
+}
+
+/* -----------------------------------------------------------------------------
+   isAlive determines whether the given closure is still alive (after
+   a garbage collection) or not.  It returns the new address of the
+   closure if it is alive, or NULL otherwise.
+
+   NOTE: Use it before compaction only!
+   -------------------------------------------------------------------------- */
+
+
+StgClosure *
+isAlive(StgClosure *p)
+{
+  const StgInfoTable *info;
+  bdescr *bd;
+
+  while (1) {
+
+    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+    info = get_itbl(p);
+
+    // ignore static closures 
+    //
+    // ToDo: for static closures, check the static link field.
+    // Problem here is that we sometimes don't set the link field, eg.
+    // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
+    //
+    if (!HEAP_ALLOCED(p)) {
+	return p;
+    }
+
+    // ignore closures in generations that we're not collecting. 
+    bd = Bdescr((P_)p);
+    if (bd->gen_no > N) {
+	return p;
+    }
+
+    // if it's a pointer into to-space, then we're done
+    if (bd->flags & BF_EVACUATED) {
+	return p;
+    }
+
+    // large objects use the evacuated flag
+    if (bd->flags & BF_LARGE) {
+	return NULL;
+    }
+
+    // check the mark bit for compacted steps
+    if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
+	return p;
+    }
+
+    switch (info->type) {
+
+    case IND:
+    case IND_STATIC:
+    case IND_PERM:
+    case IND_OLDGEN:		// rely on compatible layout with StgInd 
+    case IND_OLDGEN_PERM:
+      // follow indirections 
+      p = ((StgInd *)p)->indirectee;
+      continue;
+
+    case EVACUATED:
+      // alive! 
+      return ((StgEvacuated *)p)->evacuee;
+
+    case TSO:
+      if (((StgTSO *)p)->what_next == ThreadRelocated) {
+	p = (StgClosure *)((StgTSO *)p)->link;
+	continue;
+      } 
+      return NULL;
+
+    default:
+      // dead. 
+      return NULL;
+    }
+  }
+}
+
+static void
+mark_root(StgClosure **root)
+{
+  *root = evacuate(*root);
+}
+
+/* -----------------------------------------------------------------------------
+   Initialising the static object & mutable lists
+   -------------------------------------------------------------------------- */
+
+static void
+zero_static_object_list(StgClosure* first_static)
+{
+  StgClosure* p;
+  StgClosure* link;
+  const StgInfoTable *info;
+
+  for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
+    info = get_itbl(p);
+    link = *STATIC_LINK(info, p);
+    *STATIC_LINK(info,p) = NULL;
+  }
+}
+
+/* -----------------------------------------------------------------------------
+   Reverting CAFs
+   -------------------------------------------------------------------------- */
+
+void
+revertCAFs( void )
+{
+    StgIndStatic *c;
+
+    for (c = (StgIndStatic *)revertible_caf_list; c != NULL; 
+	 c = (StgIndStatic *)c->static_link) 
+    {
+	SET_INFO(c, c->saved_info);
+	c->saved_info = NULL;
+	// could, but not necessary: c->static_link = NULL; 
+    }
+    revertible_caf_list = NULL;
+}
+
+void
+markCAFs( evac_fn evac )
+{
+    StgIndStatic *c;
+
+    for (c = (StgIndStatic *)caf_list; c != NULL; 
+	 c = (StgIndStatic *)c->static_link) 
+    {
+	evac(&c->indirectee);
+    }
+    for (c = (StgIndStatic *)revertible_caf_list; c != NULL; 
+	 c = (StgIndStatic *)c->static_link) 
+    {
+	evac(&c->indirectee);
+    }
+}
+
+/* -----------------------------------------------------------------------------
+   Sanity code for CAF garbage collection.
+
+   With DEBUG turned on, we manage a CAF list in addition to the SRT
+   mechanism.  After GC, we run down the CAF list and blackhole any
+   CAFs which have been garbage collected.  This means we get an error
+   whenever the program tries to enter a garbage collected CAF.
+
+   Any garbage collected CAFs are taken off the CAF list at the same
+   time. 
+   -------------------------------------------------------------------------- */
+
+#if 0 && defined(DEBUG)
+
+static void
+gcCAFs(void)
+{
+  StgClosure*  p;
+  StgClosure** pp;
+  const StgInfoTable *info;
+  nat i;
+
+  i = 0;
+  p = caf_list;
+  pp = &caf_list;
+
+  while (p != NULL) {
+    
+    info = get_itbl(p);
+
+    ASSERT(info->type == IND_STATIC);
+
+    if (STATIC_LINK(info,p) == NULL) {
+	debugTrace(DEBUG_gccafs, "CAF gc'd at 0x%04lx", (long)p);
+	// black hole it 
+	SET_INFO(p,&stg_BLACKHOLE_info);
+	p = STATIC_LINK2(info,p);
+	*pp = p;
+    }
+    else {
+      pp = &STATIC_LINK2(info,p);
+      p = *pp;
+      i++;
+    }
+
+  }
+
+  debugTrace(DEBUG_gccafs, "%d CAFs live", i); 
+}
+#endif
+
+/* -----------------------------------------------------------------------------
+ * Debugging
+ * -------------------------------------------------------------------------- */
+
+#if DEBUG
+void
+printMutableList(generation *gen)
+{
+    bdescr *bd;
+    StgPtr p;
+
+    debugBelch("mutable list %p: ", gen->mut_list);
+
+    for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
+	for (p = bd->start; p < bd->free; p++) {
+	    debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));
+	}
+    }
+    debugBelch("\n");
+}
+#endif /* DEBUG */
diff --git a/rts/sm/GC.h b/rts/sm/GC.h
new file mode 100644
index 0000000000..519925e452
--- /dev/null
+++ b/rts/sm/GC.h
@@ -0,0 +1,39 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Generational garbage collector
+ *
+ * ---------------------------------------------------------------------------*/
+
+#ifndef GC_H
+#define GC_H
+
+extern nat N;
+extern rtsBool major_gc;
+extern nat evac_gen;
+extern rtsBool eager_promotion;
+extern rtsBool failed_to_evac;
+
+extern StgClosure* static_objects;
+extern StgClosure* scavenged_static_objects;
+
+extern bdescr *mark_stack_bdescr;
+extern StgPtr *mark_stack;
+extern StgPtr *mark_sp;
+extern StgPtr *mark_splim;
+
+extern rtsBool mark_stack_overflowed;
+extern bdescr *oldgen_scan_bd;
+extern StgPtr  oldgen_scan;
+
+extern lnat new_blocks;		 // blocks allocated during this GC 
+extern lnat new_scavd_blocks;	 // ditto, but depth-first blocks
+
+#ifdef DEBUG
+extern nat mutlist_MUTVARS, mutlist_MUTARRS, mutlist_OTHERS;
+#endif
+
+StgClosure * isAlive(StgClosure *p);
+
+#endif /* GC_H */
diff --git a/rts/sm/GCUtils.c b/rts/sm/GCUtils.c
new file mode 100644
index 0000000000..6e1fb302d8
--- /dev/null
+++ b/rts/sm/GCUtils.c
@@ -0,0 +1,79 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Generational garbage collector: utilities
+ *
+ * ---------------------------------------------------------------------------*/
+
+#include "Rts.h"
+#include "Storage.h"
+#include "GC.h"
+#include "GCUtils.h"
+
+/* -----------------------------------------------------------------------------
+   Allocate a new to-space block in the given step.
+   -------------------------------------------------------------------------- */
+
+bdescr *
+gc_alloc_block(step *stp)
+{
+    bdescr *bd = allocBlock();
+    bd->gen_no = stp->gen_no;
+    bd->step = stp;
+    bd->link = NULL;
+
+    // blocks in to-space in generations up to and including N
+    // get the BF_EVACUATED flag.
+    if (stp->gen_no <= N) {
+	bd->flags = BF_EVACUATED;
+    } else {
+	bd->flags = 0;
+    }
+
+    // Start a new to-space block, chain it on after the previous one.
+    if (stp->hp_bd != NULL) {
+	stp->hp_bd->free = stp->hp;
+	stp->hp_bd->link = bd;
+    }
+
+    stp->hp_bd = bd;
+    stp->hp    = bd->start;
+    stp->hpLim = stp->hp + BLOCK_SIZE_W;
+
+    stp->n_blocks++;
+    new_blocks++;
+
+    return bd;
+}
+
+bdescr *
+gc_alloc_scavd_block(step *stp)
+{
+    bdescr *bd = allocBlock();
+    bd->gen_no = stp->gen_no;
+    bd->step = stp;
+
+    // blocks in to-space in generations up to and including N
+    // get the BF_EVACUATED flag.
+    if (stp->gen_no <= N) {
+	bd->flags = BF_EVACUATED;
+    } else {
+	bd->flags = 0;
+    }
+
+    bd->link = stp->blocks;
+    stp->blocks = bd;
+
+    if (stp->scavd_hp != NULL) {
+	Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
+    }
+    stp->scavd_hp    = bd->start;
+    stp->scavd_hpLim = stp->scavd_hp + BLOCK_SIZE_W;
+
+    stp->n_blocks++;
+    new_scavd_blocks++;
+
+    return bd;
+}
+
diff --git a/rts/sm/GCUtils.h b/rts/sm/GCUtils.h
new file mode 100644
index 0000000000..c110323d80
--- /dev/null
+++ b/rts/sm/GCUtils.h
@@ -0,0 +1,10 @@
+/* ----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Generational garbage collector: utilities
+ *
+ * --------------------------------------------------------------------------*/
+
+bdescr *gc_alloc_block(step *stp);
+bdescr *gc_alloc_scavd_block(step *stp);
diff --git a/rts/MBlock.c b/rts/sm/MBlock.c
index 85fe02da6e..85fe02da6e 100644
--- a/rts/MBlock.c
+++ b/rts/sm/MBlock.c
diff --git a/rts/MBlock.h b/rts/sm/MBlock.h
index 1cc0dc5a1f..1cc0dc5a1f 100644
--- a/rts/MBlock.h
+++ b/rts/sm/MBlock.h
diff --git a/rts/sm/MarkWeak.c b/rts/sm/MarkWeak.c
new file mode 100644
index 0000000000..0042dbdeab
--- /dev/null
+++ b/rts/sm/MarkWeak.c
@@ -0,0 +1,325 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Weak pointers and weak-like things in the GC
+ *
+ * ---------------------------------------------------------------------------*/
+
+#include "Rts.h"
+#include "Storage.h"
+#include "MarkWeak.h"
+#include "GC.h"
+#include "Evac.h"
+#include "Trace.h"
+#include "Schedule.h"
+
+/* -----------------------------------------------------------------------------
+   Weak Pointers
+
+   traverse_weak_ptr_list is called possibly many times during garbage
+   collection.  It returns a flag indicating whether it did any work
+   (i.e. called evacuate on any live pointers).
+
+   Invariant: traverse_weak_ptr_list is called when the heap is in an
+   idempotent state.  That means that there are no pending
+   evacuate/scavenge operations.  This invariant helps the weak
+   pointer code decide which weak pointers are dead - if there are no
+   new live weak pointers, then all the currently unreachable ones are
+   dead.
+
+   For generational GC: we just don't try to finalize weak pointers in
+   older generations than the one we're collecting.  This could
+   probably be optimised by keeping per-generation lists of weak
+   pointers, but for a few weak pointers this scheme will work.
+
+   There are three distinct stages to processing weak pointers:
+
+   - weak_stage == WeakPtrs
+
+     We process all the weak pointers whos keys are alive (evacuate
+     their values and finalizers), and repeat until we can find no new
+     live keys.  If no live keys are found in this pass, then we
+     evacuate the finalizers of all the dead weak pointers in order to
+     run them.
+
+   - weak_stage == WeakThreads
+
+     Now, we discover which *threads* are still alive.  Pointers to
+     threads from the all_threads and main thread lists are the
+     weakest of all: a pointers from the finalizer of a dead weak
+     pointer can keep a thread alive.  Any threads found to be unreachable
+     are evacuated and placed on the resurrected_threads list so we 
+     can send them a signal later.
+
+   - weak_stage == WeakDone
+
+     No more evacuation is done.
+
+   -------------------------------------------------------------------------- */
+
+/* Which stage of processing various kinds of weak pointer are we at?
+ * (see traverse_weak_ptr_list() below for discussion).
+ */
+typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
+static WeakStage weak_stage;
+
+/* Weak pointers
+ */
+StgWeak *old_weak_ptr_list; // also pending finaliser list
+
+/* List of all threads during GC
+ */
+StgTSO *resurrected_threads;
+static StgTSO *old_all_threads;
+
+void
+initWeakForGC(void)
+{
+    old_weak_ptr_list = weak_ptr_list;
+    weak_ptr_list = NULL;
+    weak_stage = WeakPtrs;
+
+    /* The all_threads list is like the weak_ptr_list.  
+     * See traverseWeakPtrList() for the details.
+     */
+    old_all_threads = all_threads;
+    all_threads = END_TSO_QUEUE;
+    resurrected_threads = END_TSO_QUEUE;
+}
+
+rtsBool 
+traverseWeakPtrList(void)
+{
+  StgWeak *w, **last_w, *next_w;
+  StgClosure *new;
+  rtsBool flag = rtsFalse;
+
+  switch (weak_stage) {
+
+  case WeakDone:
+      return rtsFalse;
+
+  case WeakPtrs:
+      /* doesn't matter where we evacuate values/finalizers to, since
+       * these pointers are treated as roots (iff the keys are alive).
+       */
+      evac_gen = 0;
+      
+      last_w = &old_weak_ptr_list;
+      for (w = old_weak_ptr_list; w != NULL; w = next_w) {
+	  
+	  /* There might be a DEAD_WEAK on the list if finalizeWeak# was
+	   * called on a live weak pointer object.  Just remove it.
+	   */
+	  if (w->header.info == &stg_DEAD_WEAK_info) {
+	      next_w = ((StgDeadWeak *)w)->link;
+	      *last_w = next_w;
+	      continue;
+	  }
+	  
+	  switch (get_itbl(w)->type) {
+
+	  case EVACUATED:
+	      next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
+	      *last_w = next_w;
+	      continue;
+
+	  case WEAK:
+	      /* Now, check whether the key is reachable.
+	       */
+	      new = isAlive(w->key);
+	      if (new != NULL) {
+		  w->key = new;
+		  // evacuate the value and finalizer 
+		  w->value = evacuate(w->value);
+		  w->finalizer = evacuate(w->finalizer);
+		  // remove this weak ptr from the old_weak_ptr list 
+		  *last_w = w->link;
+		  // and put it on the new weak ptr list 
+		  next_w  = w->link;
+		  w->link = weak_ptr_list;
+		  weak_ptr_list = w;
+		  flag = rtsTrue;
+
+		  debugTrace(DEBUG_weak, 
+			     "weak pointer still alive at %p -> %p",
+			     w, w->key);
+		  continue;
+	      }
+	      else {
+		  last_w = &(w->link);
+		  next_w = w->link;
+		  continue;
+	      }
+
+	  default:
+	      barf("traverseWeakPtrList: not WEAK");
+	  }
+      }
+      
+      /* If we didn't make any changes, then we can go round and kill all
+       * the dead weak pointers.  The old_weak_ptr list is used as a list
+       * of pending finalizers later on.
+       */
+      if (flag == rtsFalse) {
+	  for (w = old_weak_ptr_list; w; w = w->link) {
+	      w->finalizer = evacuate(w->finalizer);
+	  }
+
+	  // Next, move to the WeakThreads stage after fully
+	  // scavenging the finalizers we've just evacuated.
+	  weak_stage = WeakThreads;
+      }
+
+      return rtsTrue;
+
+  case WeakThreads:
+      /* Now deal with the all_threads list, which behaves somewhat like
+       * the weak ptr list.  If we discover any threads that are about to
+       * become garbage, we wake them up and administer an exception.
+       */
+      {
+	  StgTSO *t, *tmp, *next, **prev;
+	  
+	  prev = &old_all_threads;
+	  for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
+	      
+	      tmp = (StgTSO *)isAlive((StgClosure *)t);
+	      
+	      if (tmp != NULL) {
+		  t = tmp;
+	      }
+	      
+	      ASSERT(get_itbl(t)->type == TSO);
+	      switch (t->what_next) {
+	      case ThreadRelocated:
+		  next = t->link;
+		  *prev = next;
+		  continue;
+	      case ThreadKilled:
+	      case ThreadComplete:
+		  // finshed or died.  The thread might still be alive, but we
+		  // don't keep it on the all_threads list.  Don't forget to
+		  // stub out its global_link field.
+		  next = t->global_link;
+		  t->global_link = END_TSO_QUEUE;
+		  *prev = next;
+		  continue;
+	      default:
+		  ;
+	      }
+	      
+	      if (tmp == NULL) {
+		  // not alive (yet): leave this thread on the
+		  // old_all_threads list.
+		  prev = &(t->global_link);
+		  next = t->global_link;
+	      } 
+	      else {
+		  // alive: move this thread onto the all_threads list.
+		  next = t->global_link;
+		  t->global_link = all_threads;
+		  all_threads  = t;
+		  *prev = next;
+	      }
+	  }
+      }
+      
+      /* If we evacuated any threads, we need to go back to the scavenger.
+       */
+      if (flag) return rtsTrue;
+
+      /* And resurrect any threads which were about to become garbage.
+       */
+      {
+	  StgTSO *t, *tmp, *next;
+	  for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
+	      next = t->global_link;
+	      tmp = (StgTSO *)evacuate((StgClosure *)t);
+	      tmp->global_link = resurrected_threads;
+	      resurrected_threads = tmp;
+	  }
+      }
+      
+      /* Finally, we can update the blackhole_queue.  This queue
+       * simply strings together TSOs blocked on black holes, it is
+       * not intended to keep anything alive.  Hence, we do not follow
+       * pointers on the blackhole_queue until now, when we have
+       * determined which TSOs are otherwise reachable.  We know at
+       * this point that all TSOs have been evacuated, however.
+       */
+      { 
+	  StgTSO **pt;
+	  for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
+	      *pt = (StgTSO *)isAlive((StgClosure *)*pt);
+	      ASSERT(*pt != NULL);
+	  }
+      }
+
+      weak_stage = WeakDone;  // *now* we're done,
+      return rtsTrue;         // but one more round of scavenging, please
+
+  default:
+      barf("traverse_weak_ptr_list");
+      return rtsTrue;
+  }
+
+}
+
+/* -----------------------------------------------------------------------------
+   The blackhole queue
+   
+   Threads on this list behave like weak pointers during the normal
+   phase of garbage collection: if the blackhole is reachable, then
+   the thread is reachable too.
+   -------------------------------------------------------------------------- */
+rtsBool
+traverseBlackholeQueue (void)
+{
+    StgTSO *prev, *t, *tmp;
+    rtsBool flag;
+
+    flag = rtsFalse;
+    prev = NULL;
+
+    for (t = blackhole_queue; t != END_TSO_QUEUE; prev=t, t = t->link) {
+	if (! (tmp = (StgTSO *)isAlive((StgClosure*)t))) {
+	    if (isAlive(t->block_info.closure)) {
+		t = (StgTSO *)evacuate((StgClosure *)t);
+		if (prev) prev->link = t;
+		flag = rtsTrue;
+	    }
+	}
+    }
+    return flag;
+}
+
+/* -----------------------------------------------------------------------------
+   After GC, the live weak pointer list may have forwarding pointers
+   on it, because a weak pointer object was evacuated after being
+   moved to the live weak pointer list.  We remove those forwarding
+   pointers here.
+
+   Also, we don't consider weak pointer objects to be reachable, but
+   we must nevertheless consider them to be "live" and retain them.
+   Therefore any weak pointer objects which haven't as yet been
+   evacuated need to be evacuated now.
+   -------------------------------------------------------------------------- */
+
+void
+markWeakPtrList ( void )
+{
+  StgWeak *w, **last_w;
+
+  last_w = &weak_ptr_list;
+  for (w = weak_ptr_list; w; w = w->link) {
+      // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
+      ASSERT(w->header.info == &stg_DEAD_WEAK_info 
+	     || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
+      w = (StgWeak *)evacuate((StgClosure *)w);
+      *last_w = w;
+      last_w = &(w->link);
+  }
+}
+
diff --git a/rts/sm/MarkWeak.h b/rts/sm/MarkWeak.h
new file mode 100644
index 0000000000..0b5bd1ed8f
--- /dev/null
+++ b/rts/sm/MarkWeak.h
@@ -0,0 +1,15 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Weak pointers and weak-like things in the GC
+ *
+ * ---------------------------------------------------------------------------*/
+
+extern StgWeak *old_weak_ptr_list;
+extern StgTSO *resurrected_threads;
+
+void    initWeakForGC          ( void );
+rtsBool traverseWeakPtrList    ( void );
+void    markWeakPtrList        ( void );
+rtsBool traverseBlackholeQueue ( void );
diff --git a/rts/OSMem.h b/rts/sm/OSMem.h
index 417f106948..417f106948 100644
--- a/rts/OSMem.h
+++ b/rts/sm/OSMem.h
diff --git a/rts/sm/README b/rts/sm/README
new file mode 100644
index 0000000000..61cb7d2c06
--- /dev/null
+++ b/rts/sm/README
@@ -0,0 +1,11 @@
+The Storage Manager
+===================
+
+This directory contains the storage manager and garbage collector.
+The interfaces exported from here are:
+
+  Storage.h (in ../includes)
+  Block.h (in ../includes)
+  GC.h
+  Arena.h
+  BlockAlloc.h
diff --git a/rts/sm/Scav.c b/rts/sm/Scav.c
new file mode 100644
index 0000000000..26b33f479e
--- /dev/null
+++ b/rts/sm/Scav.c
@@ -0,0 +1,1929 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Generational garbage collector: scavenging functions
+ *
+ * ---------------------------------------------------------------------------*/
+
+#include "Rts.h"
+#include "Storage.h"
+#include "MBlock.h"
+#include "GC.h"
+#include "Compact.h"
+#include "Evac.h"
+#include "Scav.h"
+#include "Apply.h"
+#include "Trace.h"
+#include "LdvProfile.h"
+
+static void scavenge_stack (StgPtr p, StgPtr stack_end);
+
+static void scavenge_large_bitmap (StgPtr p, 
+				   StgLargeBitmap *large_bitmap, 
+				   nat size );
+
+/* Similar to scavenge_large_bitmap(), but we don't write back the
+ * pointers we get back from evacuate().
+ */
+static void
+scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
+{
+    nat i, b, size;
+    StgWord bitmap;
+    StgClosure **p;
+    
+    b = 0;
+    bitmap = large_srt->l.bitmap[b];
+    size   = (nat)large_srt->l.size;
+    p      = (StgClosure **)large_srt->srt;
+    for (i = 0; i < size; ) {
+	if ((bitmap & 1) != 0) {
+	    evacuate(*p);
+	}
+	i++;
+	p++;
+	if (i % BITS_IN(W_) == 0) {
+	    b++;
+	    bitmap = large_srt->l.bitmap[b];
+	} else {
+	    bitmap = bitmap >> 1;
+	}
+    }
+}
+
+/* evacuate the SRT.  If srt_bitmap is zero, then there isn't an
+ * srt field in the info table.  That's ok, because we'll
+ * never dereference it.
+ */
+STATIC_INLINE void
+scavenge_srt (StgClosure **srt, nat srt_bitmap)
+{
+  nat bitmap;
+  StgClosure **p;
+
+  bitmap = srt_bitmap;
+  p = srt;
+
+  if (bitmap == (StgHalfWord)(-1)) {  
+      scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
+      return;
+  }
+
+  while (bitmap != 0) {
+      if ((bitmap & 1) != 0) {
+#ifdef ENABLE_WIN32_DLL_SUPPORT
+	  // Special-case to handle references to closures hiding out in DLLs, since
+	  // double indirections required to get at those. The code generator knows
+	  // which is which when generating the SRT, so it stores the (indirect)
+	  // reference to the DLL closure in the table by first adding one to it.
+	  // We check for this here, and undo the addition before evacuating it.
+	  // 
+	  // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
+	  // closure that's fixed at link-time, and no extra magic is required.
+	  if ( (unsigned long)(*srt) & 0x1 ) {
+	      evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
+	  } else {
+	      evacuate(*p);
+	  }
+#else
+	  evacuate(*p);
+#endif
+      }
+      p++;
+      bitmap = bitmap >> 1;
+  }
+}
+
+
+STATIC_INLINE void
+scavenge_thunk_srt(const StgInfoTable *info)
+{
+    StgThunkInfoTable *thunk_info;
+
+    if (!major_gc) return;
+
+    thunk_info = itbl_to_thunk_itbl(info);
+    scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
+}
+
+STATIC_INLINE void
+scavenge_fun_srt(const StgInfoTable *info)
+{
+    StgFunInfoTable *fun_info;
+
+    if (!major_gc) return;
+  
+    fun_info = itbl_to_fun_itbl(info);
+    scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
+}
+
+/* -----------------------------------------------------------------------------
+   Scavenge a TSO.
+   -------------------------------------------------------------------------- */
+
+static void
+scavengeTSO (StgTSO *tso)
+{
+    if (   tso->why_blocked == BlockedOnMVar
+	|| tso->why_blocked == BlockedOnBlackHole
+	|| tso->why_blocked == BlockedOnException
+#if defined(PAR)
+	|| tso->why_blocked == BlockedOnGA
+	|| tso->why_blocked == BlockedOnGA_NoSend
+#endif
+	) {
+	tso->block_info.closure = evacuate(tso->block_info.closure);
+    }
+    tso->blocked_exceptions = 
+	(StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
+    
+    // We don't always chase the link field: TSOs on the blackhole
+    // queue are not automatically alive, so the link field is a
+    // "weak" pointer in that case.
+    if (tso->why_blocked != BlockedOnBlackHole) {
+	tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
+    }
+
+    // scavange current transaction record
+    tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
+    
+    // scavenge this thread's stack 
+    scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
+}
+
+/* -----------------------------------------------------------------------------
+   Blocks of function args occur on the stack (at the top) and
+   in PAPs.
+   -------------------------------------------------------------------------- */
+
+STATIC_INLINE StgPtr
+scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
+{
+    StgPtr p;
+    StgWord bitmap;
+    nat size;
+
+    p = (StgPtr)args;
+    switch (fun_info->f.fun_type) {
+    case ARG_GEN:
+	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
+	size = BITMAP_SIZE(fun_info->f.b.bitmap);
+	goto small_bitmap;
+    case ARG_GEN_BIG:
+	size = GET_FUN_LARGE_BITMAP(fun_info)->size;
+	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
+	p += size;
+	break;
+    default:
+	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
+	size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
+    small_bitmap:
+	while (size > 0) {
+	    if ((bitmap & 1) == 0) {
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    }
+	    p++;
+	    bitmap = bitmap >> 1;
+	    size--;
+	}
+	break;
+    }
+    return p;
+}
+
+STATIC_INLINE StgPtr
+scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
+{
+    StgPtr p;
+    StgWord bitmap;
+    StgFunInfoTable *fun_info;
+    
+    fun_info = get_fun_itbl(fun);
+    ASSERT(fun_info->i.type != PAP);
+    p = (StgPtr)payload;
+
+    switch (fun_info->f.fun_type) {
+    case ARG_GEN:
+	bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
+	goto small_bitmap;
+    case ARG_GEN_BIG:
+	scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
+	p += size;
+	break;
+    case ARG_BCO:
+	scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
+	p += size;
+	break;
+    default:
+	bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
+    small_bitmap:
+	while (size > 0) {
+	    if ((bitmap & 1) == 0) {
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    }
+	    p++;
+	    bitmap = bitmap >> 1;
+	    size--;
+	}
+	break;
+    }
+    return p;
+}
+
+STATIC_INLINE StgPtr
+scavenge_PAP (StgPAP *pap)
+{
+    pap->fun = evacuate(pap->fun);
+    return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
+}
+
+STATIC_INLINE StgPtr
+scavenge_AP (StgAP *ap)
+{
+    ap->fun = evacuate(ap->fun);
+    return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
+}
+
+/* -----------------------------------------------------------------------------
+   Scavenge a given step until there are no more objects in this step
+   to scavenge.
+
+   evac_gen is set by the caller to be either zero (for a step in a
+   generation < N) or G where G is the generation of the step being
+   scavenged.  
+
+   We sometimes temporarily change evac_gen back to zero if we're
+   scavenging a mutable object where early promotion isn't such a good
+   idea.  
+   -------------------------------------------------------------------------- */
+
+void
+scavenge(step *stp)
+{
+  StgPtr p, q;
+  StgInfoTable *info;
+  bdescr *bd;
+  nat saved_evac_gen = evac_gen;
+
+  p = stp->scan;
+  bd = stp->scan_bd;
+
+  failed_to_evac = rtsFalse;
+
+  /* scavenge phase - standard breadth-first scavenging of the
+   * evacuated objects 
+   */
+
+  while (bd != stp->hp_bd || p < stp->hp) {
+
+    // If we're at the end of this block, move on to the next block 
+    if (bd != stp->hp_bd && p == bd->free) {
+      bd = bd->link;
+      p = bd->start;
+      continue;
+    }
+
+    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+    info = get_itbl((StgClosure *)p);
+    
+    ASSERT(thunk_selector_depth == 0);
+
+    q = p;
+    switch (info->type) {
+
+    case MVAR:
+    { 
+	StgMVar *mvar = ((StgMVar *)p);
+	evac_gen = 0;
+	mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
+	mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
+	mvar->value = evacuate((StgClosure *)mvar->value);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable.
+	p += sizeofW(StgMVar);
+	break;
+    }
+
+    case FUN_2_0:
+	scavenge_fun_srt(info);
+	((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
+	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 2;
+	break;
+
+    case THUNK_2_0:
+	scavenge_thunk_srt(info);
+	((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
+	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 2;
+	break;
+
+    case CONSTR_2_0:
+	((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
+	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 2;
+	break;
+	
+    case THUNK_1_0:
+	scavenge_thunk_srt(info);
+	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 1;
+	break;
+	
+    case FUN_1_0:
+	scavenge_fun_srt(info);
+    case CONSTR_1_0:
+	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 1;
+	break;
+	
+    case THUNK_0_1:
+	scavenge_thunk_srt(info);
+	p += sizeofW(StgThunk) + 1;
+	break;
+	
+    case FUN_0_1:
+	scavenge_fun_srt(info);
+    case CONSTR_0_1:
+	p += sizeofW(StgHeader) + 1;
+	break;
+	
+    case THUNK_0_2:
+	scavenge_thunk_srt(info);
+	p += sizeofW(StgThunk) + 2;
+	break;
+	
+    case FUN_0_2:
+	scavenge_fun_srt(info);
+    case CONSTR_0_2:
+	p += sizeofW(StgHeader) + 2;
+	break;
+	
+    case THUNK_1_1:
+	scavenge_thunk_srt(info);
+	((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	p += sizeofW(StgThunk) + 2;
+	break;
+
+    case FUN_1_1:
+	scavenge_fun_srt(info);
+    case CONSTR_1_1:
+	((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	p += sizeofW(StgHeader) + 2;
+	break;
+	
+    case FUN:
+	scavenge_fun_srt(info);
+	goto gen_obj;
+
+    case THUNK:
+    {
+	StgPtr end;
+
+	scavenge_thunk_srt(info);
+	end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
+	for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+	p += info->layout.payload.nptrs;
+	break;
+    }
+	
+    gen_obj:
+    case CONSTR:
+    case WEAK:
+    case STABLE_NAME:
+    {
+	StgPtr end;
+
+	end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
+	for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+	p += info->layout.payload.nptrs;
+	break;
+    }
+
+    case BCO: {
+	StgBCO *bco = (StgBCO *)p;
+	bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
+	bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
+	bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
+	bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
+	p += bco_sizeW(bco);
+	break;
+    }
+
+    case IND_PERM:
+      if (stp->gen->no != 0) {
+#ifdef PROFILING
+        // @LDV profiling
+        // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an 
+        // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
+        LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
+#endif        
+        // 
+        // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
+        //
+	SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
+
+        // We pretend that p has just been created.
+        LDV_RECORD_CREATE((StgClosure *)p);
+      }
+	// fall through 
+    case IND_OLDGEN_PERM:
+	((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
+	p += sizeofW(StgInd);
+	break;
+
+    case MUT_VAR_CLEAN:
+    case MUT_VAR_DIRTY: {
+	rtsBool saved_eager_promotion = eager_promotion;
+
+	eager_promotion = rtsFalse;
+	((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
+	eager_promotion = saved_eager_promotion;
+
+	if (failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
+	}
+	p += sizeofW(StgMutVar);
+	break;
+    }
+
+    case CAF_BLACKHOLE:
+    case SE_CAF_BLACKHOLE:
+    case SE_BLACKHOLE:
+    case BLACKHOLE:
+	p += BLACKHOLE_sizeW();
+	break;
+
+    case THUNK_SELECTOR:
+    { 
+	StgSelector *s = (StgSelector *)p;
+	s->selectee = evacuate(s->selectee);
+	p += THUNK_SELECTOR_sizeW();
+	break;
+    }
+
+    // A chunk of stack saved in a heap object
+    case AP_STACK:
+    {
+	StgAP_STACK *ap = (StgAP_STACK *)p;
+
+	ap->fun = evacuate(ap->fun);
+	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
+	p = (StgPtr)ap->payload + ap->size;
+	break;
+    }
+
+    case PAP:
+	p = scavenge_PAP((StgPAP *)p);
+	break;
+
+    case AP:
+	p = scavenge_AP((StgAP *)p);
+	break;
+
+    case ARR_WORDS:
+	// nothing to follow 
+	p += arr_words_sizeW((StgArrWords *)p);
+	break;
+
+    case MUT_ARR_PTRS_CLEAN:
+    case MUT_ARR_PTRS_DIRTY:
+	// follow everything 
+    {
+	StgPtr next;
+	rtsBool saved_eager;
+
+	// We don't eagerly promote objects pointed to by a mutable
+	// array, but if we find the array only points to objects in
+	// the same or an older generation, we mark it "clean" and
+	// avoid traversing it during minor GCs.
+	saved_eager = eager_promotion;
+	eager_promotion = rtsFalse;
+	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+	eager_promotion = saved_eager;
+
+	if (failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
+	}
+
+	failed_to_evac = rtsTrue; // always put it on the mutable list.
+	break;
+    }
+
+    case MUT_ARR_PTRS_FROZEN:
+    case MUT_ARR_PTRS_FROZEN0:
+	// follow everything 
+    {
+	StgPtr next;
+
+	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+
+	// If we're going to put this object on the mutable list, then
+	// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
+	if (failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
+	}
+	break;
+    }
+
+    case TSO:
+    { 
+	StgTSO *tso = (StgTSO *)p;
+	rtsBool saved_eager = eager_promotion;
+
+	eager_promotion = rtsFalse;
+	scavengeTSO(tso);
+	eager_promotion = saved_eager;
+
+	if (failed_to_evac) {
+	    tso->flags |= TSO_DIRTY;
+	} else {
+	    tso->flags &= ~TSO_DIRTY;
+	}
+
+	failed_to_evac = rtsTrue; // always on the mutable list
+	p += tso_sizeW(tso);
+	break;
+    }
+
+#if defined(PAR)
+    case RBH:
+    { 
+#if 0
+	nat size, ptrs, nonptrs, vhs;
+	char str[80];
+	StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
+#endif
+	StgRBH *rbh = (StgRBH *)p;
+	(StgClosure *)rbh->blocking_queue = 
+	    evacuate((StgClosure *)rbh->blocking_queue);
+	failed_to_evac = rtsTrue;  // mutable anyhow.
+	debugTrace(DEBUG_gc, "scavenge: RBH %p (%s) (new blocking_queue link=%p)",
+		   p, info_type(p), (StgClosure *)rbh->blocking_queue);
+	// ToDo: use size of reverted closure here!
+	p += BLACKHOLE_sizeW(); 
+	break;
+    }
+
+    case BLOCKED_FETCH:
+    { 
+	StgBlockedFetch *bf = (StgBlockedFetch *)p;
+	// follow the pointer to the node which is being demanded 
+	(StgClosure *)bf->node = 
+	    evacuate((StgClosure *)bf->node);
+	// follow the link to the rest of the blocking queue 
+	(StgClosure *)bf->link = 
+	    evacuate((StgClosure *)bf->link);
+	debugTrace(DEBUG_gc, "scavenge: %p (%s); node is now %p; exciting, isn't it",
+		   bf, info_type((StgClosure *)bf), 
+		   bf->node, info_type(bf->node)));
+	p += sizeofW(StgBlockedFetch);
+	break;
+    }
+
+#ifdef DIST
+    case REMOTE_REF:
+#endif
+    case FETCH_ME:
+	p += sizeofW(StgFetchMe);
+	break; // nothing to do in this case
+
+    case FETCH_ME_BQ:
+    { 
+	StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
+	(StgClosure *)fmbq->blocking_queue = 
+	    evacuate((StgClosure *)fmbq->blocking_queue);
+	debugTrace(DEBUG_gc, "scavenge: %p (%s) exciting, isn't it",
+		   p, info_type((StgClosure *)p)));
+	p += sizeofW(StgFetchMeBlockingQueue);
+	break;
+    }
+#endif
+
+    case TVAR_WATCH_QUEUE:
+      {
+	StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
+	evac_gen = 0;
+	wq->closure = (StgClosure*)evacuate((StgClosure*)wq->closure);
+	wq->next_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->next_queue_entry);
+	wq->prev_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTVarWatchQueue);
+	break;
+      }
+
+    case TVAR:
+      {
+	StgTVar *tvar = ((StgTVar *) p);
+	evac_gen = 0;
+	tvar->current_value = evacuate((StgClosure*)tvar->current_value);
+	tvar->first_watch_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)tvar->first_watch_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTVar);
+	break;
+      }
+
+    case TREC_HEADER:
+      {
+        StgTRecHeader *trec = ((StgTRecHeader *) p);
+        evac_gen = 0;
+	trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
+	trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
+	trec->invariants_to_check = (StgInvariantCheckQueue *)evacuate((StgClosure*)trec->invariants_to_check);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTRecHeader);
+        break;
+      }
+
+    case TREC_CHUNK:
+      {
+	StgWord i;
+	StgTRecChunk *tc = ((StgTRecChunk *) p);
+	TRecEntry *e = &(tc -> entries[0]);
+	evac_gen = 0;
+	tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
+	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
+	  e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
+	  e->expected_value = evacuate((StgClosure*)e->expected_value);
+	  e->new_value = evacuate((StgClosure*)e->new_value);
+	}
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgTRecChunk);
+	break;
+      }
+
+    case ATOMIC_INVARIANT:
+      {
+        StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
+        evac_gen = 0;
+	invariant->code = (StgClosure *)evacuate(invariant->code);
+	invariant->last_execution = (StgTRecHeader *)evacuate((StgClosure*)invariant->last_execution);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgAtomicInvariant);
+        break;
+      }
+
+    case INVARIANT_CHECK_QUEUE:
+      {
+        StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
+        evac_gen = 0;
+	queue->invariant = (StgAtomicInvariant *)evacuate((StgClosure*)queue->invariant);
+	queue->my_execution = (StgTRecHeader *)evacuate((StgClosure*)queue->my_execution);
+	queue->next_queue_entry = (StgInvariantCheckQueue *)evacuate((StgClosure*)queue->next_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	p += sizeofW(StgInvariantCheckQueue);
+        break;
+      }
+
+    default:
+	barf("scavenge: unimplemented/strange closure type %d @ %p", 
+	     info->type, p);
+    }
+
+    /*
+     * We need to record the current object on the mutable list if
+     *  (a) It is actually mutable, or 
+     *  (b) It contains pointers to a younger generation.
+     * Case (b) arises if we didn't manage to promote everything that
+     * the current object points to into the current generation.
+     */
+    if (failed_to_evac) {
+	failed_to_evac = rtsFalse;
+	if (stp->gen_no > 0) {
+	    recordMutableGen((StgClosure *)q, stp->gen);
+	}
+    }
+  }
+
+  stp->scan_bd = bd;
+  stp->scan = p;
+}    
+
+/* -----------------------------------------------------------------------------
+   Scavenge everything on the mark stack.
+
+   This is slightly different from scavenge():
+      - we don't walk linearly through the objects, so the scavenger
+        doesn't need to advance the pointer on to the next object.
+   -------------------------------------------------------------------------- */
+
+void
+scavenge_mark_stack(void)
+{
+    StgPtr p, q;
+    StgInfoTable *info;
+    nat saved_evac_gen;
+
+    evac_gen = oldest_gen->no;
+    saved_evac_gen = evac_gen;
+
+linear_scan:
+    while (!mark_stack_empty()) {
+	p = pop_mark_stack();
+
+	ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+	info = get_itbl((StgClosure *)p);
+	
+	q = p;
+	switch (info->type) {
+	    
+	case MVAR:
+	{
+	    StgMVar *mvar = ((StgMVar *)p);
+	    evac_gen = 0;
+	    mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
+	    mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
+	    mvar->value = evacuate((StgClosure *)mvar->value);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable.
+	    break;
+	}
+
+	case FUN_2_0:
+	    scavenge_fun_srt(info);
+	    ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
+	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	    break;
+
+	case THUNK_2_0:
+	    scavenge_thunk_srt(info);
+	    ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
+	    ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	    break;
+
+	case CONSTR_2_0:
+	    ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
+	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	    break;
+	
+	case FUN_1_0:
+	case FUN_1_1:
+	    scavenge_fun_srt(info);
+	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	    break;
+
+	case THUNK_1_0:
+	case THUNK_1_1:
+	    scavenge_thunk_srt(info);
+	    ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
+	    break;
+
+	case CONSTR_1_0:
+	case CONSTR_1_1:
+	    ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
+	    break;
+	
+	case FUN_0_1:
+	case FUN_0_2:
+	    scavenge_fun_srt(info);
+	    break;
+
+	case THUNK_0_1:
+	case THUNK_0_2:
+	    scavenge_thunk_srt(info);
+	    break;
+
+	case CONSTR_0_1:
+	case CONSTR_0_2:
+	    break;
+	
+	case FUN:
+	    scavenge_fun_srt(info);
+	    goto gen_obj;
+
+	case THUNK:
+	{
+	    StgPtr end;
+	    
+	    scavenge_thunk_srt(info);
+	    end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
+	    for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    }
+	    break;
+	}
+	
+	gen_obj:
+	case CONSTR:
+	case WEAK:
+	case STABLE_NAME:
+	{
+	    StgPtr end;
+	    
+	    end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
+	    for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    }
+	    break;
+	}
+
+	case BCO: {
+	    StgBCO *bco = (StgBCO *)p;
+	    bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
+	    bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
+	    bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
+	    bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
+	    break;
+	}
+
+	case IND_PERM:
+	    // don't need to do anything here: the only possible case
+	    // is that we're in a 1-space compacting collector, with
+	    // no "old" generation.
+	    break;
+
+	case IND_OLDGEN:
+	case IND_OLDGEN_PERM:
+	    ((StgInd *)p)->indirectee = 
+		evacuate(((StgInd *)p)->indirectee);
+	    break;
+
+	case MUT_VAR_CLEAN:
+	case MUT_VAR_DIRTY: {
+	    rtsBool saved_eager_promotion = eager_promotion;
+	    
+	    eager_promotion = rtsFalse;
+	    ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
+	    eager_promotion = saved_eager_promotion;
+	    
+	    if (failed_to_evac) {
+		((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
+	    } else {
+		((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
+	    }
+	    break;
+	}
+
+	case CAF_BLACKHOLE:
+	case SE_CAF_BLACKHOLE:
+	case SE_BLACKHOLE:
+	case BLACKHOLE:
+	case ARR_WORDS:
+	    break;
+
+	case THUNK_SELECTOR:
+	{ 
+	    StgSelector *s = (StgSelector *)p;
+	    s->selectee = evacuate(s->selectee);
+	    break;
+	}
+
+	// A chunk of stack saved in a heap object
+	case AP_STACK:
+	{
+	    StgAP_STACK *ap = (StgAP_STACK *)p;
+	    
+	    ap->fun = evacuate(ap->fun);
+	    scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
+	    break;
+	}
+
+	case PAP:
+	    scavenge_PAP((StgPAP *)p);
+	    break;
+
+	case AP:
+	    scavenge_AP((StgAP *)p);
+	    break;
+      
+	case MUT_ARR_PTRS_CLEAN:
+	case MUT_ARR_PTRS_DIRTY:
+	    // follow everything 
+	{
+	    StgPtr next;
+	    rtsBool saved_eager;
+
+	    // We don't eagerly promote objects pointed to by a mutable
+	    // array, but if we find the array only points to objects in
+	    // the same or an older generation, we mark it "clean" and
+	    // avoid traversing it during minor GCs.
+	    saved_eager = eager_promotion;
+	    eager_promotion = rtsFalse;
+	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    }
+	    eager_promotion = saved_eager;
+
+	    if (failed_to_evac) {
+		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
+	    } else {
+		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
+	    }
+
+	    failed_to_evac = rtsTrue; // mutable anyhow.
+	    break;
+	}
+
+	case MUT_ARR_PTRS_FROZEN:
+	case MUT_ARR_PTRS_FROZEN0:
+	    // follow everything 
+	{
+	    StgPtr next, q = p;
+	    
+	    next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+	    for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
+		*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    }
+
+	    // If we're going to put this object on the mutable list, then
+	    // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
+	    if (failed_to_evac) {
+		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
+	    } else {
+		((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
+	    }
+	    break;
+	}
+
+	case TSO:
+	{ 
+	    StgTSO *tso = (StgTSO *)p;
+	    rtsBool saved_eager = eager_promotion;
+
+	    eager_promotion = rtsFalse;
+	    scavengeTSO(tso);
+	    eager_promotion = saved_eager;
+	    
+	    if (failed_to_evac) {
+		tso->flags |= TSO_DIRTY;
+	    } else {
+		tso->flags &= ~TSO_DIRTY;
+	    }
+	    
+	    failed_to_evac = rtsTrue; // always on the mutable list
+	    break;
+	}
+
+#if defined(PAR)
+	case RBH:
+	{ 
+#if 0
+	    nat size, ptrs, nonptrs, vhs;
+	    char str[80];
+	    StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
+#endif
+	    StgRBH *rbh = (StgRBH *)p;
+	    bh->blocking_queue = 
+		(StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
+	    failed_to_evac = rtsTrue;  // mutable anyhow.
+	    debugTrace(DEBUG_gc, "scavenge: RBH %p (%s) (new blocking_queue link=%p)",
+		       p, info_type(p), (StgClosure *)rbh->blocking_queue));
+	    break;
+	}
+	
+	case BLOCKED_FETCH:
+	{ 
+	    StgBlockedFetch *bf = (StgBlockedFetch *)p;
+	    // follow the pointer to the node which is being demanded 
+	    (StgClosure *)bf->node = 
+		evacuate((StgClosure *)bf->node);
+	    // follow the link to the rest of the blocking queue 
+	    (StgClosure *)bf->link = 
+		evacuate((StgClosure *)bf->link);
+	    debugTrace(DEBUG_gc, "scavenge: %p (%s); node is now %p; exciting, isn't it",
+		       bf, info_type((StgClosure *)bf), 
+		       bf->node, info_type(bf->node)));
+	    break;
+	}
+
+#ifdef DIST
+	case REMOTE_REF:
+#endif
+	case FETCH_ME:
+	    break; // nothing to do in this case
+
+	case FETCH_ME_BQ:
+	{ 
+	    StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
+	    (StgClosure *)fmbq->blocking_queue = 
+		evacuate((StgClosure *)fmbq->blocking_queue);
+	    debugTrace(DEBUG_gc, "scavenge: %p (%s) exciting, isn't it",
+		       p, info_type((StgClosure *)p)));
+	    break;
+	}
+#endif /* PAR */
+
+	case TVAR_WATCH_QUEUE:
+	  {
+	    StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
+	    evac_gen = 0;
+            wq->closure = (StgClosure*)evacuate((StgClosure*)wq->closure);
+	    wq->next_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->next_queue_entry);
+	    wq->prev_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
+	  
+	case TVAR:
+	  {
+	    StgTVar *tvar = ((StgTVar *) p);
+	    evac_gen = 0;
+	    tvar->current_value = evacuate((StgClosure*)tvar->current_value);
+	    tvar->first_watch_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)tvar->first_watch_queue_entry);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
+	  
+	case TREC_CHUNK:
+	  {
+	    StgWord i;
+	    StgTRecChunk *tc = ((StgTRecChunk *) p);
+	    TRecEntry *e = &(tc -> entries[0]);
+	    evac_gen = 0;
+	    tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
+	    for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
+	      e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
+	      e->expected_value = evacuate((StgClosure*)e->expected_value);
+	      e->new_value = evacuate((StgClosure*)e->new_value);
+	    }
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
+
+	case TREC_HEADER:
+	  {
+	    StgTRecHeader *trec = ((StgTRecHeader *) p);
+	    evac_gen = 0;
+	    trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
+	    trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
+  	    trec->invariants_to_check = (StgInvariantCheckQueue *)evacuate((StgClosure*)trec->invariants_to_check);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+	    break;
+	  }
+
+        case ATOMIC_INVARIANT:
+          {
+            StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
+            evac_gen = 0;
+	    invariant->code = (StgClosure *)evacuate(invariant->code);
+    	    invariant->last_execution = (StgTRecHeader *)evacuate((StgClosure*)invariant->last_execution);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+            break;
+          }
+
+        case INVARIANT_CHECK_QUEUE:
+          {
+            StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
+            evac_gen = 0;
+    	    queue->invariant = (StgAtomicInvariant *)evacuate((StgClosure*)queue->invariant);
+	    queue->my_execution = (StgTRecHeader *)evacuate((StgClosure*)queue->my_execution);
+            queue->next_queue_entry = (StgInvariantCheckQueue *)evacuate((StgClosure*)queue->next_queue_entry);
+	    evac_gen = saved_evac_gen;
+	    failed_to_evac = rtsTrue; // mutable
+            break;
+          }
+
+	default:
+	    barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p", 
+		 info->type, p);
+	}
+
+	if (failed_to_evac) {
+	    failed_to_evac = rtsFalse;
+	    if (evac_gen > 0) {
+		recordMutableGen((StgClosure *)q, &generations[evac_gen]);
+	    }
+	}
+	
+	// mark the next bit to indicate "scavenged"
+	mark(q+1, Bdescr(q));
+
+    } // while (!mark_stack_empty())
+
+    // start a new linear scan if the mark stack overflowed at some point
+    if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
+	debugTrace(DEBUG_gc, "scavenge_mark_stack: starting linear scan");
+	mark_stack_overflowed = rtsFalse;
+	oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
+	oldgen_scan = oldgen_scan_bd->start;
+    }
+
+    if (oldgen_scan_bd) {
+	// push a new thing on the mark stack
+    loop:
+	// find a closure that is marked but not scavenged, and start
+	// from there.
+	while (oldgen_scan < oldgen_scan_bd->free 
+	       && !is_marked(oldgen_scan,oldgen_scan_bd)) {
+	    oldgen_scan++;
+	}
+
+	if (oldgen_scan < oldgen_scan_bd->free) {
+
+	    // already scavenged?
+	    if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
+		oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
+		goto loop;
+	    }
+	    push_mark_stack(oldgen_scan);
+	    // ToDo: bump the linear scan by the actual size of the object
+	    oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
+	    goto linear_scan;
+	}
+
+	oldgen_scan_bd = oldgen_scan_bd->link;
+	if (oldgen_scan_bd != NULL) {
+	    oldgen_scan = oldgen_scan_bd->start;
+	    goto loop;
+	}
+    }
+}
+
+/* -----------------------------------------------------------------------------
+   Scavenge one object.
+
+   This is used for objects that are temporarily marked as mutable
+   because they contain old-to-new generation pointers.  Only certain
+   objects can have this property.
+   -------------------------------------------------------------------------- */
+
+static rtsBool
+scavenge_one(StgPtr p)
+{
+    const StgInfoTable *info;
+    nat saved_evac_gen = evac_gen;
+    rtsBool no_luck;
+    
+    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+    info = get_itbl((StgClosure *)p);
+    
+    switch (info->type) {
+	
+    case MVAR:
+    { 
+	StgMVar *mvar = ((StgMVar *)p);
+	evac_gen = 0;
+	mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
+	mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
+	mvar->value = evacuate((StgClosure *)mvar->value);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable.
+	break;
+    }
+
+    case THUNK:
+    case THUNK_1_0:
+    case THUNK_0_1:
+    case THUNK_1_1:
+    case THUNK_0_2:
+    case THUNK_2_0:
+    {
+	StgPtr q, end;
+	
+	end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
+	for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
+	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
+	}
+	break;
+    }
+
+    case FUN:
+    case FUN_1_0:			// hardly worth specialising these guys
+    case FUN_0_1:
+    case FUN_1_1:
+    case FUN_0_2:
+    case FUN_2_0:
+    case CONSTR:
+    case CONSTR_1_0:
+    case CONSTR_0_1:
+    case CONSTR_1_1:
+    case CONSTR_0_2:
+    case CONSTR_2_0:
+    case WEAK:
+    case IND_PERM:
+    {
+	StgPtr q, end;
+	
+	end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
+	for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
+	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
+	}
+	break;
+    }
+    
+    case MUT_VAR_CLEAN:
+    case MUT_VAR_DIRTY: {
+	StgPtr q = p;
+	rtsBool saved_eager_promotion = eager_promotion;
+
+	eager_promotion = rtsFalse;
+	((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
+	eager_promotion = saved_eager_promotion;
+
+	if (failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
+	}
+	break;
+    }
+
+    case CAF_BLACKHOLE:
+    case SE_CAF_BLACKHOLE:
+    case SE_BLACKHOLE:
+    case BLACKHOLE:
+	break;
+	
+    case THUNK_SELECTOR:
+    { 
+	StgSelector *s = (StgSelector *)p;
+	s->selectee = evacuate(s->selectee);
+	break;
+    }
+    
+    case AP_STACK:
+    {
+	StgAP_STACK *ap = (StgAP_STACK *)p;
+
+	ap->fun = evacuate(ap->fun);
+	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
+	p = (StgPtr)ap->payload + ap->size;
+	break;
+    }
+
+    case PAP:
+	p = scavenge_PAP((StgPAP *)p);
+	break;
+
+    case AP:
+	p = scavenge_AP((StgAP *)p);
+	break;
+
+    case ARR_WORDS:
+	// nothing to follow 
+	break;
+
+    case MUT_ARR_PTRS_CLEAN:
+    case MUT_ARR_PTRS_DIRTY:
+    {
+	StgPtr next, q;
+	rtsBool saved_eager;
+
+	// We don't eagerly promote objects pointed to by a mutable
+	// array, but if we find the array only points to objects in
+	// the same or an older generation, we mark it "clean" and
+	// avoid traversing it during minor GCs.
+	saved_eager = eager_promotion;
+	eager_promotion = rtsFalse;
+	q = p;
+	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+	eager_promotion = saved_eager;
+
+	if (failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
+	}
+
+	failed_to_evac = rtsTrue;
+	break;
+    }
+
+    case MUT_ARR_PTRS_FROZEN:
+    case MUT_ARR_PTRS_FROZEN0:
+    {
+	// follow everything 
+	StgPtr next, q=p;
+      
+	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+
+	// If we're going to put this object on the mutable list, then
+	// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
+	if (failed_to_evac) {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
+	} else {
+	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
+	}
+	break;
+    }
+
+    case TSO:
+    {
+	StgTSO *tso = (StgTSO *)p;
+	rtsBool saved_eager = eager_promotion;
+
+	eager_promotion = rtsFalse;
+	scavengeTSO(tso);
+	eager_promotion = saved_eager;
+
+	if (failed_to_evac) {
+	    tso->flags |= TSO_DIRTY;
+	} else {
+	    tso->flags &= ~TSO_DIRTY;
+	}
+
+	failed_to_evac = rtsTrue; // always on the mutable list
+	break;
+    }
+  
+#if defined(PAR)
+    case RBH:
+    { 
+#if 0
+	nat size, ptrs, nonptrs, vhs;
+	char str[80];
+	StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
+#endif
+	StgRBH *rbh = (StgRBH *)p;
+	(StgClosure *)rbh->blocking_queue = 
+	    evacuate((StgClosure *)rbh->blocking_queue);
+	failed_to_evac = rtsTrue;  // mutable anyhow.
+	debugTrace(DEBUG_gc, "scavenge: RBH %p (%s) (new blocking_queue link=%p)",
+		   p, info_type(p), (StgClosure *)rbh->blocking_queue));
+	// ToDo: use size of reverted closure here!
+	break;
+    }
+
+    case BLOCKED_FETCH:
+    { 
+	StgBlockedFetch *bf = (StgBlockedFetch *)p;
+	// follow the pointer to the node which is being demanded 
+	(StgClosure *)bf->node = 
+	    evacuate((StgClosure *)bf->node);
+	// follow the link to the rest of the blocking queue 
+	(StgClosure *)bf->link = 
+	    evacuate((StgClosure *)bf->link);
+	debugTrace(DEBUG_gc,
+		   "scavenge: %p (%s); node is now %p; exciting, isn't it",
+		   bf, info_type((StgClosure *)bf), 
+		   bf->node, info_type(bf->node)));
+	break;
+    }
+
+#ifdef DIST
+    case REMOTE_REF:
+#endif
+    case FETCH_ME:
+	break; // nothing to do in this case
+
+    case FETCH_ME_BQ:
+    { 
+	StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
+	(StgClosure *)fmbq->blocking_queue = 
+	    evacuate((StgClosure *)fmbq->blocking_queue);
+	debugTrace(DEBUG_gc, "scavenge: %p (%s) exciting, isn't it",
+		   p, info_type((StgClosure *)p)));
+	break;
+    }
+#endif
+
+    case TVAR_WATCH_QUEUE:
+      {
+	StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
+	evac_gen = 0;
+        wq->closure = (StgClosure*)evacuate((StgClosure*)wq->closure);
+        wq->next_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->next_queue_entry);
+        wq->prev_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	break;
+      }
+
+    case TVAR:
+      {
+	StgTVar *tvar = ((StgTVar *) p);
+	evac_gen = 0;
+	tvar->current_value = evacuate((StgClosure*)tvar->current_value);
+        tvar->first_watch_queue_entry = (StgTVarWatchQueue *)evacuate((StgClosure*)tvar->first_watch_queue_entry);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	break;
+      }
+
+    case TREC_HEADER:
+      {
+        StgTRecHeader *trec = ((StgTRecHeader *) p);
+        evac_gen = 0;
+	trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
+	trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
+        trec->invariants_to_check = (StgInvariantCheckQueue *)evacuate((StgClosure*)trec->invariants_to_check);
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+        break;
+      }
+
+    case TREC_CHUNK:
+      {
+	StgWord i;
+	StgTRecChunk *tc = ((StgTRecChunk *) p);
+	TRecEntry *e = &(tc -> entries[0]);
+	evac_gen = 0;
+	tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
+	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
+	  e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
+	  e->expected_value = evacuate((StgClosure*)e->expected_value);
+	  e->new_value = evacuate((StgClosure*)e->new_value);
+	}
+	evac_gen = saved_evac_gen;
+	failed_to_evac = rtsTrue; // mutable
+	break;
+      }
+
+    case ATOMIC_INVARIANT:
+    {
+      StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
+      evac_gen = 0;
+      invariant->code = (StgClosure *)evacuate(invariant->code);
+      invariant->last_execution = (StgTRecHeader *)evacuate((StgClosure*)invariant->last_execution);
+      evac_gen = saved_evac_gen;
+      failed_to_evac = rtsTrue; // mutable
+      break;
+    }
+
+    case INVARIANT_CHECK_QUEUE:
+    {
+      StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
+      evac_gen = 0;
+      queue->invariant = (StgAtomicInvariant *)evacuate((StgClosure*)queue->invariant);
+      queue->my_execution = (StgTRecHeader *)evacuate((StgClosure*)queue->my_execution);
+      queue->next_queue_entry = (StgInvariantCheckQueue *)evacuate((StgClosure*)queue->next_queue_entry);
+      evac_gen = saved_evac_gen;
+      failed_to_evac = rtsTrue; // mutable
+      break;
+    }
+
+    case IND_OLDGEN:
+    case IND_OLDGEN_PERM:
+    case IND_STATIC:
+    {
+	/* Careful here: a THUNK can be on the mutable list because
+	 * it contains pointers to young gen objects.  If such a thunk
+	 * is updated, the IND_OLDGEN will be added to the mutable
+	 * list again, and we'll scavenge it twice.  evacuate()
+	 * doesn't check whether the object has already been
+	 * evacuated, so we perform that check here.
+	 */
+	StgClosure *q = ((StgInd *)p)->indirectee;
+	if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
+	    break;
+	}
+	((StgInd *)p)->indirectee = evacuate(q);
+    }
+
+#if 0 && defined(DEBUG)
+      if (RtsFlags.DebugFlags.gc) 
+      /* Debugging code to print out the size of the thing we just
+       * promoted 
+       */
+      { 
+	StgPtr start = gen->steps[0].scan;
+	bdescr *start_bd = gen->steps[0].scan_bd;
+	nat size = 0;
+	scavenge(&gen->steps[0]);
+	if (start_bd != gen->steps[0].scan_bd) {
+	  size += (P_)BLOCK_ROUND_UP(start) - start;
+	  start_bd = start_bd->link;
+	  while (start_bd != gen->steps[0].scan_bd) {
+	    size += BLOCK_SIZE_W;
+	    start_bd = start_bd->link;
+	  }
+	  size += gen->steps[0].scan -
+	    (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
+	} else {
+	  size = gen->steps[0].scan - start;
+	}
+	debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
+      }
+#endif
+      break;
+
+    default:
+	barf("scavenge_one: strange object %d", (int)(info->type));
+    }    
+
+    no_luck = failed_to_evac;
+    failed_to_evac = rtsFalse;
+    return (no_luck);
+}
+
+/* -----------------------------------------------------------------------------
+   Scavenging mutable lists.
+
+   We treat the mutable list of each generation > N (i.e. all the
+   generations older than the one being collected) as roots.  We also
+   remove non-mutable objects from the mutable list at this point.
+   -------------------------------------------------------------------------- */
+
+void
+scavenge_mutable_list(generation *gen)
+{
+    bdescr *bd;
+    StgPtr p, q;
+
+    bd = gen->saved_mut_list;
+
+    evac_gen = gen->no;
+    for (; bd != NULL; bd = bd->link) {
+	for (q = bd->start; q < bd->free; q++) {
+	    p = (StgPtr)*q;
+	    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+
+#ifdef DEBUG	    
+	    switch (get_itbl((StgClosure *)p)->type) {
+	    case MUT_VAR_CLEAN:
+		barf("MUT_VAR_CLEAN on mutable list");
+	    case MUT_VAR_DIRTY:
+		mutlist_MUTVARS++; break;
+	    case MUT_ARR_PTRS_CLEAN:
+	    case MUT_ARR_PTRS_DIRTY:
+	    case MUT_ARR_PTRS_FROZEN:
+	    case MUT_ARR_PTRS_FROZEN0:
+		mutlist_MUTARRS++; break;
+	    default:
+		mutlist_OTHERS++; break;
+	    }
+#endif
+
+	    // Check whether this object is "clean", that is it
+	    // definitely doesn't point into a young generation.
+	    // Clean objects don't need to be scavenged.  Some clean
+	    // objects (MUT_VAR_CLEAN) are not kept on the mutable
+	    // list at all; others, such as MUT_ARR_PTRS_CLEAN and
+	    // TSO, are always on the mutable list.
+	    //
+	    switch (get_itbl((StgClosure *)p)->type) {
+	    case MUT_ARR_PTRS_CLEAN:
+		recordMutableGen((StgClosure *)p,gen);
+		continue;
+	    case TSO: {
+		StgTSO *tso = (StgTSO *)p;
+		if ((tso->flags & TSO_DIRTY) == 0) {
+		    // A clean TSO: we don't have to traverse its
+		    // stack.  However, we *do* follow the link field:
+		    // we don't want to have to mark a TSO dirty just
+		    // because we put it on a different queue.
+		    if (tso->why_blocked != BlockedOnBlackHole) {
+			tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
+		    }
+		    recordMutableGen((StgClosure *)p,gen);
+		    continue;
+		}
+	    }
+	    default:
+		;
+	    }
+
+	    if (scavenge_one(p)) {
+		// didn't manage to promote everything, so put the
+		// object back on the list.
+		recordMutableGen((StgClosure *)p,gen);
+	    }
+	}
+    }
+
+    // free the old mut_list
+    freeChain(gen->saved_mut_list);
+    gen->saved_mut_list = NULL;
+}
+
+/* -----------------------------------------------------------------------------
+   Scavenging the static objects.
+
+   We treat the mutable list of each generation > N (i.e. all the
+   generations older than the one being collected) as roots.  We also
+   remove non-mutable objects from the mutable list at this point.
+   -------------------------------------------------------------------------- */
+
+void
+scavenge_static(void)
+{
+  StgClosure* p = static_objects;
+  const StgInfoTable *info;
+
+  /* Always evacuate straight to the oldest generation for static
+   * objects */
+  evac_gen = oldest_gen->no;
+
+  /* keep going until we've scavenged all the objects on the linked
+     list... */
+  while (p != END_OF_STATIC_LIST) {
+
+    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
+    info = get_itbl(p);
+    /*
+    if (info->type==RBH)
+      info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
+    */
+    // make sure the info pointer is into text space 
+    
+    /* Take this object *off* the static_objects list,
+     * and put it on the scavenged_static_objects list.
+     */
+    static_objects = *STATIC_LINK(info,p);
+    *STATIC_LINK(info,p) = scavenged_static_objects;
+    scavenged_static_objects = p;
+    
+    switch (info -> type) {
+      
+    case IND_STATIC:
+      {
+	StgInd *ind = (StgInd *)p;
+	ind->indirectee = evacuate(ind->indirectee);
+
+	/* might fail to evacuate it, in which case we have to pop it
+	 * back on the mutable list of the oldest generation.  We
+	 * leave it *on* the scavenged_static_objects list, though,
+	 * in case we visit this object again.
+	 */
+	if (failed_to_evac) {
+	  failed_to_evac = rtsFalse;
+	  recordMutableGen((StgClosure *)p,oldest_gen);
+	}
+	break;
+      }
+      
+    case THUNK_STATIC:
+      scavenge_thunk_srt(info);
+      break;
+
+    case FUN_STATIC:
+      scavenge_fun_srt(info);
+      break;
+      
+    case CONSTR_STATIC:
+      {	
+	StgPtr q, next;
+	
+	next = (P_)p->payload + info->layout.payload.ptrs;
+	// evacuate the pointers 
+	for (q = (P_)p->payload; q < next; q++) {
+	    *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
+	}
+	break;
+      }
+      
+    default:
+      barf("scavenge_static: strange closure %d", (int)(info->type));
+    }
+
+    ASSERT(failed_to_evac == rtsFalse);
+
+    /* get the next static object from the list.  Remember, there might
+     * be more stuff on this list now that we've done some evacuating!
+     * (static_objects is a global)
+     */
+    p = static_objects;
+  }
+}
+
+/* -----------------------------------------------------------------------------
+   scavenge a chunk of memory described by a bitmap
+   -------------------------------------------------------------------------- */
+
+static void
+scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
+{
+    nat i, b;
+    StgWord bitmap;
+    
+    b = 0;
+    bitmap = large_bitmap->bitmap[b];
+    for (i = 0; i < size; ) {
+	if ((bitmap & 1) == 0) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+	i++;
+	p++;
+	if (i % BITS_IN(W_) == 0) {
+	    b++;
+	    bitmap = large_bitmap->bitmap[b];
+	} else {
+	    bitmap = bitmap >> 1;
+	}
+    }
+}
+
+STATIC_INLINE StgPtr
+scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
+{
+    while (size > 0) {
+	if ((bitmap & 1) == 0) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	}
+	p++;
+	bitmap = bitmap >> 1;
+	size--;
+    }
+    return p;
+}
+
+/* -----------------------------------------------------------------------------
+   scavenge_stack walks over a section of stack and evacuates all the
+   objects pointed to by it.  We can use the same code for walking
+   AP_STACK_UPDs, since these are just sections of copied stack.
+   -------------------------------------------------------------------------- */
+
+static void
+scavenge_stack(StgPtr p, StgPtr stack_end)
+{
+  const StgRetInfoTable* info;
+  StgWord bitmap;
+  nat size;
+
+  /* 
+   * Each time around this loop, we are looking at a chunk of stack
+   * that starts with an activation record. 
+   */
+
+  while (p < stack_end) {
+    info  = get_ret_itbl((StgClosure *)p);
+      
+    switch (info->i.type) {
+	
+    case UPDATE_FRAME:
+	// In SMP, we can get update frames that point to indirections
+	// when two threads evaluate the same thunk.  We do attempt to
+	// discover this situation in threadPaused(), but it's
+	// possible that the following sequence occurs:
+	//
+	//        A             B
+	//                  enter T
+	//     enter T
+	//     blackhole T
+	//                  update T
+	//     GC
+	//
+	// Now T is an indirection, and the update frame is already
+	// marked on A's stack, so we won't traverse it again in
+	// threadPaused().  We could traverse the whole stack again
+	// before GC, but that seems like overkill.
+	//
+	// Scavenging this update frame as normal would be disastrous;
+	// the updatee would end up pointing to the value.  So we turn
+	// the indirection into an IND_PERM, so that evacuate will
+	// copy the indirection into the old generation instead of
+	// discarding it.
+	if (get_itbl(((StgUpdateFrame *)p)->updatee)->type == IND) {
+	    ((StgUpdateFrame *)p)->updatee->header.info = 
+		(StgInfoTable *)&stg_IND_PERM_info;
+	}
+	((StgUpdateFrame *)p)->updatee 
+	    = evacuate(((StgUpdateFrame *)p)->updatee);
+	p += sizeofW(StgUpdateFrame);
+	continue;
+
+      // small bitmap (< 32 entries, or 64 on a 64-bit machine) 
+    case CATCH_STM_FRAME:
+    case CATCH_RETRY_FRAME:
+    case ATOMICALLY_FRAME:
+    case STOP_FRAME:
+    case CATCH_FRAME:
+    case RET_SMALL:
+    case RET_VEC_SMALL:
+	bitmap = BITMAP_BITS(info->i.layout.bitmap);
+	size   = BITMAP_SIZE(info->i.layout.bitmap);
+	// NOTE: the payload starts immediately after the info-ptr, we
+	// don't have an StgHeader in the same sense as a heap closure.
+	p++;
+	p = scavenge_small_bitmap(p, size, bitmap);
+
+    follow_srt:
+	if (major_gc) 
+	    scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
+	continue;
+
+    case RET_BCO: {
+	StgBCO *bco;
+	nat size;
+
+	p++;
+	*p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	bco = (StgBCO *)*p;
+	p++;
+	size = BCO_BITMAP_SIZE(bco);
+	scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
+	p += size;
+	continue;
+    }
+
+      // large bitmap (> 32 entries, or > 64 on a 64-bit machine) 
+    case RET_BIG:
+    case RET_VEC_BIG:
+    {
+	nat size;
+
+	size = GET_LARGE_BITMAP(&info->i)->size;
+	p++;
+	scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
+	p += size;
+	// and don't forget to follow the SRT 
+	goto follow_srt;
+    }
+
+      // Dynamic bitmap: the mask is stored on the stack, and
+      // there are a number of non-pointers followed by a number
+      // of pointers above the bitmapped area.  (see StgMacros.h,
+      // HEAP_CHK_GEN).
+    case RET_DYN:
+    {
+	StgWord dyn;
+	dyn = ((StgRetDyn *)p)->liveness;
+
+	// traverse the bitmap first
+	bitmap = RET_DYN_LIVENESS(dyn);
+	p      = (P_)&((StgRetDyn *)p)->payload[0];
+	size   = RET_DYN_BITMAP_SIZE;
+	p = scavenge_small_bitmap(p, size, bitmap);
+
+	// skip over the non-ptr words
+	p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
+	
+	// follow the ptr words
+	for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
+	    *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
+	    p++;
+	}
+	continue;
+    }
+
+    case RET_FUN:
+    {
+	StgRetFun *ret_fun = (StgRetFun *)p;
+	StgFunInfoTable *fun_info;
+
+	ret_fun->fun = evacuate(ret_fun->fun);
+ 	fun_info = get_fun_itbl(ret_fun->fun);
+	p = scavenge_arg_block(fun_info, ret_fun->payload);
+	goto follow_srt;
+    }
+
+    default:
+	barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
+    }
+  }		     
+}
+
+/*-----------------------------------------------------------------------------
+  scavenge the large object list.
+
+  evac_gen set by caller; similar games played with evac_gen as with
+  scavenge() - see comment at the top of scavenge().  Most large
+  objects are (repeatedly) mutable, so most of the time evac_gen will
+  be zero.
+  --------------------------------------------------------------------------- */
+
+void
+scavenge_large(step *stp)
+{
+  bdescr *bd;
+  StgPtr p;
+
+  bd = stp->new_large_objects;
+
+  for (; bd != NULL; bd = stp->new_large_objects) {
+
+    /* take this object *off* the large objects list and put it on
+     * the scavenged large objects list.  This is so that we can
+     * treat new_large_objects as a stack and push new objects on
+     * the front when evacuating.
+     */
+    stp->new_large_objects = bd->link;
+    dbl_link_onto(bd, &stp->scavenged_large_objects);
+
+    // update the block count in this step.
+    stp->n_scavenged_large_blocks += bd->blocks;
+
+    p = bd->start;
+    if (scavenge_one(p)) {
+	if (stp->gen_no > 0) {
+	    recordMutableGen((StgClosure *)p, stp->gen);
+	}
+    }
+  }
+}
+
diff --git a/rts/sm/Scav.h b/rts/sm/Scav.h
new file mode 100644
index 0000000000..010a81013c
--- /dev/null
+++ b/rts/sm/Scav.h
@@ -0,0 +1,13 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team 1998-2006
+ *
+ * Generational garbage collector: scavenging functions
+ *
+ * ---------------------------------------------------------------------------*/
+
+void scavenge                ( step * );
+void scavenge_mark_stack     ( void );
+void scavenge_large          ( step * );
+void scavenge_static         ( void );
+void scavenge_mutable_list   ( generation *g );
diff --git a/rts/Storage.c b/rts/sm/Storage.c
index a657ce8d3e..a657ce8d3e 100644
--- a/rts/Storage.c
+++ b/rts/sm/Storage.c