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/* -----------------------------------------------------------------------------
*
* (c) The GHC Team 1998-2008
*
* Functions called from outside the GC need to be separate from GC.c,
* because GC.c is compiled with register variable(s).
*
* ---------------------------------------------------------------------------*/
#include "rts/PosixSource.h"
#include "Rts.h"
#include "GC.h"
#include "CheckUnload.h"
#include "Storage.h"
#include "Compact.h"
#include "Task.h"
#include "Capability.h"
#include "Trace.h"
#include "Schedule.h"
// DO NOT include "GCTDecl.h", we don't want the register variable
/* -----------------------------------------------------------------------------
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!
It untags and (if needed) retags pointers to closures.
-------------------------------------------------------------------------- */
StgClosure *
isAlive(StgClosure *p)
{
const StgInfoTable *info;
bdescr *bd;
StgWord tag;
StgClosure *q;
while (1) {
/* The tag and the pointer are split, to be merged later when needed. */
tag = GET_CLOSURE_TAG(p);
q = UNTAG_CLOSURE(p);
ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
// ignore static closures
//
// ToDo: This means we never look through IND_STATIC, which means
// isRetainer needs to handle the IND_STATIC case rather than
// raising an error.
//
// 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_NOCAFs.
//
if (!HEAP_ALLOCED_GC(q)) {
return p;
}
// ignore closures in generations that we're not collecting.
bd = Bdescr((P_)q);
// isAlive is used when scavenging moving generations, before the mark
// phase. Because we don't know alive-ness of objects before the mark phase
// we have to conservatively treat objects in the non-moving generation as
// alive here.
if (bd->flags & BF_NONMOVING) {
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 generations
if ((bd->flags & BF_MARKED) && is_marked((P_)q,bd)) {
return p;
}
info = RELAXED_LOAD(&q->header.info);
if (IS_FORWARDING_PTR(info)) {
// alive!
return TAG_CLOSURE(tag,(StgClosure*)UN_FORWARDING_PTR(info));
}
info = INFO_PTR_TO_STRUCT(info);
load_load_barrier();
switch (info->type) {
case IND:
case IND_STATIC:
// follow indirections
p = ((StgInd *)q)->indirectee;
continue;
case BLACKHOLE:
p = ((StgInd*)q)->indirectee;
if (GET_CLOSURE_TAG(p) != 0) {
continue;
} else {
return NULL;
}
default:
// dead.
return NULL;
}
}
}
/* -----------------------------------------------------------------------------
Reverting CAFs
-------------------------------------------------------------------------- */
void
revertCAFs( void )
{
StgIndStatic *c = revertible_caf_list;
while (c != (StgIndStatic *) END_OF_CAF_LIST) {
c = (StgIndStatic *)UNTAG_STATIC_LIST_PTR(c);
StgIndStatic *next = (StgIndStatic *) c->static_link;
SET_INFO((StgClosure *)c, c->saved_info);
c->saved_info = NULL;
// We must reset static_link lest the major GC finds that
// static_flag==3 and will consequently ignore references
// into code that we are trying to unload. This would result
// in reachable object code being unloaded prematurely.
// See #16842.
c->static_link = NULL;
c = next;
}
revertible_caf_list = (StgIndStatic*)END_OF_CAF_LIST;
}
void
markCAFs (evac_fn evac, void *user)
{
/* N.B. We must both ensure that the indirectee is
* evacuated and that we let the linker know that the CAF
* itself is still reachable, lest it be collected (see
* #20649).
*/
for (StgIndStatic *c = dyn_caf_list;
((StgWord) c | STATIC_FLAG_LIST) != (StgWord)END_OF_CAF_LIST;
c = (StgIndStatic *)c->static_link)
{
c = (StgIndStatic *)UNTAG_STATIC_LIST_PTR(c);
evac(user, &c->indirectee);
// See Note [Object unloading] in CheckUnload.c
if (unload_mark_needed) markObjectCode(c);
}
for (StgIndStatic *c = revertible_caf_list;
((StgWord) c | STATIC_FLAG_LIST) != (StgWord)END_OF_CAF_LIST;
c = (StgIndStatic *)c->static_link)
{
c = (StgIndStatic *)UNTAG_STATIC_LIST_PTR(c);
evac(user, &c->indirectee);
// See Note [Object unloading] in CheckUnload.c
if (unload_mark_needed) markObjectCode(c);
}
}
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