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Unified Diff: src/x64/full-codegen-x64.cc

Issue 297203002: Skip write barriers in the fast case when setting up local context. (Closed) Base URL: git@github.com:v8/v8.git@master
Patch Set: Created 6 years, 7 months ago
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Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 76225da08271ce1b3d3dcde16ecf6170fa95cb0e..97c9c5cdebc0ef9b35bd9293a7f49ec090491a11 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -199,6 +199,7 @@ void FullCodeGenerator::Generate() {
int heap_slots = info->scope()->num_heap_slots() - Context::MIN_CONTEXT_SLOTS;
if (heap_slots > 0) {
Comment cmnt(masm_, "[ Allocate context");
+ bool need_write_barrier = true;
// Argument to NewContext is the function, which is still in rdi.
if (FLAG_harmony_scoping && info->scope()->is_global_scope()) {
__ Push(rdi);
@@ -207,6 +208,8 @@ void FullCodeGenerator::Generate() {
} else if (heap_slots <= FastNewContextStub::kMaximumSlots) {
FastNewContextStub stub(isolate(), heap_slots);
__ CallStub(&stub);
+ // Result of FastNewContextStub is always in new space.
+ need_write_barrier = false;
} else {
__ Push(rdi);
__ CallRuntime(Runtime::kHiddenNewFunctionContext, 1);
@@ -230,8 +233,15 @@ void FullCodeGenerator::Generate() {
int context_offset = Context::SlotOffset(var->index());
__ movp(Operand(rsi, context_offset), rax);
// Update the write barrier. This clobbers rax and rbx.
- __ RecordWriteContextSlot(
- rsi, context_offset, rax, rbx, kDontSaveFPRegs);
+ if (need_write_barrier) {
+ __ RecordWriteContextSlot(
+ rsi, context_offset, rax, rbx, kDontSaveFPRegs);
+ } else if (FLAG_debug_code) {
+ Label done;
+ __ JumpIfInNewSpace(rsi, rax, &done, Label::kNear);
+ __ Abort(kExpectedNewSpaceObject);
+ __ bind(&done);
+ }
}
}
}
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