Reviewers: Michael Starzinger, Hannes Payer,
Message:
Almost no more write barriers in pretenured GeneratePayloadTree... :-)
Description:
Eliminate further write barriers for old space allocations.
Storing a map or an immortal immovable object to old space
allocations requires no write barriers if the object is the
new space dominator.
Please review this at https://codereview.chromium.org/271103002/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+11, -0 lines):
M src/hydrogen-instructions.h
Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index
85d1e7549fa38aa6a051ab0f0feaa970878674ec..b6620a0e0b3922d34745c2d15c58a4f23c0290d4
100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -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()) {
--
--
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