Make allocatePinned use local storage, and other refactorings

This is a batch of refactoring to remove some of the GC's global
state, as we move towards CPU-local GC.  

  - allocateLocal() now allocates large objects into the local
    nursery, rather than taking a global lock and allocating
    then in gen 0 step 0.

  - allocatePinned() was still allocating from global storage and
    taking a lock each time, now it uses local storage. 
    (mallocForeignPtrBytes should be faster with -threaded).
    
  - We had a gen 0 step 0, distinct from the nurseries, which are
    stored in a separate nurseries[] array.  This is slightly strange.
    I removed the g0s0 global that pointed to gen 0 step 0, and
    removed all uses of it.  I think now we don't use gen 0 step 0 at
    all, except possibly when there is only one generation.  Possibly
    more tidying up is needed here.

  - I removed the global allocate() function, and renamed
    allocateLocal() to allocate().

  - the alloc_blocks global is gone.  MAYBE_GC() and
    doYouWantToGC() now check the local nursery only.

1 files changed, 3 insertions, 0 deletions

diff --git a/rts/Capability.h b/rts/Capability.h
index 3f01bf3d88..ff6e368130 100644
--- a/rts/Capability.h
+++ b/rts/Capability.h
@@ -69,6 +69,9 @@ struct Capability_ {
     bdescr **mut_lists;
     bdescr **saved_mut_lists; // tmp use during GC
 
+    // block for allocating pinned objects into
+    bdescr *pinned_object_block;
+
     // Context switch flag. We used to have one global flag, now one 
     // per capability. Locks required  : none (conflicts are harmless)
     int context_switch;