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Retire ShortCircuitConsString.

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BUG=

Review URL: https://codereview.chromium.org/1267313002

Cr-Commit-Position: refs/heads/master@{#30015}
This commit is contained in:
hpayer 2015-08-04 12:18:47 -07:00 committed by Commit bot
parent 9d7ebcf7f5
commit 53be2063cc
1 changed files with 2 additions and 37 deletions
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39
src/heap/mark-compact.cc
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@ -1201,41 +1201,6 @@ MarkCompactCollector::~MarkCompactCollector() {
}
static inline HeapObject* ShortCircuitConsString(Object** p) {
// Optimization: If the heap object pointed to by p is a non-internalized
// cons string whose right substring is HEAP->empty_string, update
// it in place to its left substring. Return the updated value.
//
// Here we assume that if we change *p, we replace it with a heap object
// (i.e., the left substring of a cons string is always a heap object).
//
// The check performed is:
// object->IsConsString() && !object->IsInternalizedString() &&
// (ConsString::cast(object)->second() == HEAP->empty_string())
// except the maps for the object and its possible substrings might be
// marked.
HeapObject* object = HeapObject::cast(*p);
Map* map = object->map();
InstanceType type = map->instance_type();
if (!IsShortcutCandidate(type)) return object;
Object* second = reinterpret_cast<ConsString*>(object)->second();
Heap* heap = map->GetHeap();
if (second != heap->empty_string()) {
return object;
}
// Since we don't have the object's start, it is impossible to update the
// page dirty marks. Therefore, we only replace the string with its left
// substring when page dirty marks do not change.
Object* first = reinterpret_cast<ConsString*>(object)->first();
if (!heap->InNewSpace(object) && heap->InNewSpace(first)) return object;
*p = first;
return HeapObject::cast(first);
}
class MarkCompactMarkingVisitor
: public StaticMarkingVisitor<MarkCompactMarkingVisitor> {
public:
@ -1293,7 +1258,7 @@ class MarkCompactMarkingVisitor
INLINE(static void MarkObjectByPointer(MarkCompactCollector* collector,
HeapObject* object, Object** p)) {
if (!(*p)->IsHeapObject()) return;
HeapObject* target_object = ShortCircuitConsString(p);
HeapObject* target_object = HeapObject::cast(*p);
collector->RecordSlot(object, p, target_object);
MarkBit mark = Marking::MarkBitFrom(target_object);
collector->MarkObject(target_object, mark);
@ -1671,7 +1636,7 @@ class RootMarkingVisitor : public ObjectVisitor {
if (!(*p)->IsHeapObject()) return;
// Replace flat cons strings in place.
HeapObject* object = ShortCircuitConsString(p);
HeapObject* object = HeapObject::cast(*p);
MarkBit mark_bit = Marking::MarkBitFrom(object);
if (Marking::IsBlackOrGrey(mark_bit)) return;