From 4fd78904be3edda9e9c0e3b8e591125308649e1b Mon Sep 17 00:00:00 2001
From: "plind44@gmail.com"
 <plind44@gmail.com@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Mon, 26 May 2014 14:40:55 +0000
Subject: [PATCH] MIPS: Skip write barriers in the fast case when setting up
 local context.

Port r21481 (5973b48)

Original commit message:
The FastNewContextStub always allocates in new space, so we don't
need to update the write barrier when copying the parameters to
the newly allocated context.

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/302633002

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21500 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/mips/full-codegen-mips.cc    | 14 ++++++++++++--
 src/mips/lithium-codegen-mips.cc | 14 ++++++++++++--
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index 5a47a7ce46..7310eee88a 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -219,6 +219,7 @@ void FullCodeGenerator::Generate() {
   if (heap_slots > 0) {
     Comment cmnt(masm_, "[ Allocate context");
     // Argument to NewContext is the function, which is still in a1.
+    bool need_write_barrier = true;
     if (FLAG_harmony_scoping && info->scope()->is_global_scope()) {
       __ push(a1);
       __ Push(info->scope()->GetScopeInfo());
@@ -226,6 +227,8 @@ 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(a1);
       __ CallRuntime(Runtime::kHiddenNewFunctionContext, 1);
@@ -249,8 +252,15 @@ void FullCodeGenerator::Generate() {
         __ sw(a0, target);
 
         // Update the write barrier.
-        __ RecordWriteContextSlot(
-            cp, target.offset(), a0, a3, kRAHasBeenSaved, kDontSaveFPRegs);
+        if (need_write_barrier) {
+          __ RecordWriteContextSlot(
+              cp, target.offset(), a0, a3, kRAHasBeenSaved, kDontSaveFPRegs);
+        } else if (FLAG_debug_code) {
+          Label done;
+          __ JumpIfInNewSpace(cp, a0, &done);
+          __ Abort(kExpectedNewSpaceObject);
+          __ bind(&done);
+        }
       }
     }
   }
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index fd30b1a8ff..f1deb38705 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -198,10 +198,13 @@ bool LCodeGen::GeneratePrologue() {
   int heap_slots = info()->num_heap_slots() - Context::MIN_CONTEXT_SLOTS;
   if (heap_slots > 0) {
     Comment(";;; Allocate local context");
+    bool need_write_barrier = true;
     // Argument to NewContext is the function, which is in a1.
     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(a1);
       __ CallRuntime(Runtime::kHiddenNewFunctionContext, 1);
@@ -224,8 +227,15 @@ bool LCodeGen::GeneratePrologue() {
         MemOperand target = ContextOperand(cp, var->index());
         __ sw(a0, target);
         // Update the write barrier. This clobbers a3 and a0.
-        __ RecordWriteContextSlot(
-            cp, target.offset(), a0, a3, GetRAState(), kSaveFPRegs);
+        if (need_write_barrier) {
+          __ RecordWriteContextSlot(
+              cp, target.offset(), a0, a3, GetRAState(), kSaveFPRegs);
+        } else if (FLAG_debug_code) {
+          Label done;
+          __ JumpIfInNewSpace(cp, a0, &done);
+          __ Abort(kExpectedNewSpaceObject);
+          __ bind(&done);
+        }
       }
     }
     Comment(";;; End allocate local context");