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Eliminate further write barriers for old space allocations.

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Storing a map or an immortal immovable object to old space
allocations requires no write barriers if the object is the
new space dominator.

R=hpayer@chromium.org, mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/271103002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21216 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
bmeurer@chromium.org 2014-05-09 12:06:48 +00:00
parent c3b5f70414
commit e8547d3ffe
1 changed files with 11 additions and 0 deletions
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11
src/hydrogen-instructions.h
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@ -3545,6 +3545,10 @@ class HConstant V8_FINAL : public HTemplateInstruction<0> {
return instance_type_ == CELL_TYPE || instance_type_ == PROPERTY_CELL_TYPE;
}
bool IsMap() const {
return instance_type_ == MAP_TYPE;
}
virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
return Representation::None();
}
@ -5708,6 +5712,13 @@ inline bool ReceiverObjectNeedsWriteBarrier(HValue* object,
if (HAllocate::cast(object)->IsNewSpaceAllocation()) {
return false;
}
// Storing a map or an immortal immovable object requires no write barriers
// if the object is the new space dominator.
if (value->IsConstant() &&
(HConstant::cast(value)->IsMap() ||
HConstant::cast(value)->ImmortalImmovable())) {
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()) {