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Skip write barrier if value and object originate from the same allocation.

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R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/101993002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18243 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
bmeurer@chromium.org 2013-12-04 06:06:57 +00:00
parent 1d6710c933
commit 86fa1cfceb
1 changed files with 20 additions and 8 deletions
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28
src/hydrogen-instructions.h
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@ -5652,11 +5652,10 @@ inline bool StoringValueNeedsWriteBarrier(HValue* value) {
inline bool ReceiverObjectNeedsWriteBarrier(HValue* object,
HValue* value,
HValue* new_space_dominator) {
if (object->IsInnerAllocatedObject()) {
return ReceiverObjectNeedsWriteBarrier(
HInnerAllocatedObject::cast(object)->base_object(),
new_space_dominator);
while (object->IsInnerAllocatedObject()) {
object = HInnerAllocatedObject::cast(object)->base_object();
}
if (object->IsConstant() && HConstant::cast(object)->IsCell()) {
return false;
@ -5668,7 +5667,17 @@ inline bool ReceiverObjectNeedsWriteBarrier(HValue* object,
}
if (object != new_space_dominator) return true;
if (object->IsAllocate()) {
return !HAllocate::cast(object)->IsNewSpaceAllocation();
// Stores to new space allocations require no write barriers if the object
// is the new space dominator.
if (HAllocate::cast(object)->IsNewSpaceAllocation()) {
return false;
}
// Likewise we don't need a write barrier if we store a value that
// originates from the same allocation (via allocation folding).
while (value->IsInnerAllocatedObject()) {
value = HInnerAllocatedObject::cast(value)->base_object();
}
return object != value;
}
return true;
}
@ -6589,12 +6598,14 @@ class HStoreNamedField V8_FINAL : public HTemplateInstruction<3> {
if (field_representation().IsInteger32()) return false;
if (field_representation().IsExternal()) return false;
return StoringValueNeedsWriteBarrier(value()) &&
ReceiverObjectNeedsWriteBarrier(object(), new_space_dominator());
ReceiverObjectNeedsWriteBarrier(object(), value(),
new_space_dominator());
}
bool NeedsWriteBarrierForMap() {
if (IsSkipWriteBarrier()) return false;
return ReceiverObjectNeedsWriteBarrier(object(), new_space_dominator());
return ReceiverObjectNeedsWriteBarrier(object(), transition(),
new_space_dominator());
}
Representation field_representation() const {
@ -6756,7 +6767,8 @@ class HStoreKeyed V8_FINAL
return false;
} else {
return StoringValueNeedsWriteBarrier(value()) &&
ReceiverObjectNeedsWriteBarrier(elements(), new_space_dominator());
ReceiverObjectNeedsWriteBarrier(elements(), value(),
new_space_dominator());
}
}