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When scavenging update source slot before migrating object it points to.

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Source slot might belong to a dead old object and we might allocate a new object over it when evacuating a new space object this slot points to. In this case if we update slot after migrating object we will write into migrated object.

R=erik.corry@gmail.com

Review URL: http://codereview.chromium.org/8698022

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10082 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
vegorov@chromium.org 2011-11-29 10:02:38 +00:00
parent e3eb71e991
commit 23c15e495c
1 changed files with 16 additions and 8 deletions
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18
src/heap.cc
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@ -1486,7 +1486,7 @@ class ScavengingVisitor : public StaticVisitorBase {
// Helper function used by CopyObject to copy a source object to an
// allocated target object and update the forwarding pointer in the source
// object. Returns the target object.
INLINE(static HeapObject* MigrateObject(Heap* heap,
INLINE(static void MigrateObject(Heap* heap,
HeapObject* source,
HeapObject* target,
int size)) {
@ -1515,8 +1515,6 @@ class ScavengingVisitor : public StaticVisitorBase {
MemoryChunk::IncrementLiveBytes(target->address(), size);
}
}
return target;
}
template<ObjectContents object_contents, SizeRestriction size_restriction>
@ -1547,7 +1545,12 @@ class ScavengingVisitor : public StaticVisitorBase {
Object* result = NULL; // Initialization to please compiler.
if (maybe_result->ToObject(&result)) {
HeapObject* target = HeapObject::cast(result);
*slot = MigrateObject(heap, object , target, object_size);
// Order is important: slot might be inside of the target if target
// was allocated over a dead object and slot comes from the store
// buffer.
*slot = target;
MigrateObject(heap, object, target, object_size);
if (object_contents == POINTER_OBJECT) {
heap->promotion_queue()->insert(target, object_size);
@ -1560,8 +1563,13 @@ class ScavengingVisitor : public StaticVisitorBase {
MaybeObject* allocation = heap->new_space()->AllocateRaw(object_size);
heap->promotion_queue()->SetNewLimit(heap->new_space()->top());
Object* result = allocation->ToObjectUnchecked();
HeapObject* target = HeapObject::cast(result);
*slot = MigrateObject(heap, object, HeapObject::cast(result), object_size);
// Order is important: slot might be inside of the target if target
// was allocated over a dead object and slot comes from the store
// buffer.
*slot = target;
MigrateObject(heap, object, target, object_size);
return;
}