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Further improve old space allocation write barrier elimination.

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Stores to old space allocations require no write barriers if the
object is the new space dominator and the value is not in new space.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/290173003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21360 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
bmeurer@chromium.org 2014-05-19 09:48:35 +00:00
parent 9de1ec5a78
commit 890dc24758
1 changed files with 14 additions and 13 deletions
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27
src/hydrogen-instructions.h
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@ -5702,7 +5702,7 @@ inline bool StoringValueNeedsWriteBarrier(HValue* value) {
inline bool ReceiverObjectNeedsWriteBarrier(HValue* object,
HValue* value,
HValue* new_space_dominator) {
HValue* dominator) {
while (object->IsInnerAllocatedObject()) {
object = HInnerAllocatedObject::cast(object)->base_object();
}
@ -5714,26 +5714,27 @@ inline bool ReceiverObjectNeedsWriteBarrier(HValue* object,
// Stores to external references require no write barriers
return false;
}
if (object != new_space_dominator) return true;
if (object->IsAllocate()) {
// Stores to new space allocations require no write barriers if the object
// is the new space dominator.
// We definitely need a write barrier unless the object is the allocation
// dominator.
if (object == dominator && object->IsAllocate()) {
// Stores to new space allocations require no write barriers.
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())) {
// Stores to old space allocations require no write barriers if the value is
// a constant provably not in new space.
if (value->IsConstant() && HConstant::cast(value)->NotInNewSpace()) {
return false;
}
// Likewise we don't need a write barrier if we store a value that
// originates from the same allocation (via allocation folding).
// Stores to old space allocations require no write barriers if the value is
// an old space allocation.
while (value->IsInnerAllocatedObject()) {
value = HInnerAllocatedObject::cast(value)->base_object();
}
return object != value;
if (value->IsAllocate() &&
!HAllocate::cast(value)->IsNewSpaceAllocation()) {
return false;
}
}
return true;
}