Change the handling of stack check on backward branches

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 3a621823e5a407f444f594a8066da9cf668895a6..f83fdc24c7438c7b415b7bd712aed480cbfd97d7 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1425,44 +1425,17 @@ void LCodeGen::DoBranch(LBranch* instr) {
 }
 
 
-void LCodeGen::EmitGoto(int block, LDeferredCode* deferred_stack_check) {
+void LCodeGen::EmitGoto(int block) {
   block = chunk_->LookupDestination(block);
   int next_block = GetNextEmittedBlock(current_block_);
   if (block != next_block) {
-    // Perform stack overflow check if this goto needs it before jumping.
-    if (deferred_stack_check != NULL) {
-      __ CompareRoot(rsp, Heap::kStackLimitRootIndex);
-      __ j(above_equal, chunk_->GetAssemblyLabel(block));
-      __ jmp(deferred_stack_check->entry());
-      deferred_stack_check->SetExit(chunk_->GetAssemblyLabel(block));
-    } else {
-      __ jmp(chunk_->GetAssemblyLabel(block));
-    }
+    __ jmp(chunk_->GetAssemblyLabel(block));
   }
 }
 
 
-void LCodeGen::DoDeferredStackCheck(LGoto* instr) {
-  PushSafepointRegistersScope scope(this);
-  CallRuntimeFromDeferred(Runtime::kStackGuard, 0, instr);
-}
-
-
 void LCodeGen::DoGoto(LGoto* instr) {
-  class DeferredStackCheck: public LDeferredCode {
-   public:
-    DeferredStackCheck(LCodeGen* codegen, LGoto* instr)
-        : LDeferredCode(codegen), instr_(instr) { }
-    virtual void Generate() { codegen()->DoDeferredStackCheck(instr_); }
-   private:
-    LGoto* instr_;
-  };
-
-  DeferredStackCheck* deferred = NULL;
-  if (instr->include_stack_check()) {
-    deferred = new DeferredStackCheck(this, instr);
-  }
-  EmitGoto(instr->block_id(), deferred);
+  EmitGoto(instr->block_id());
 }
 
 
@@ -4290,15 +4263,40 @@ void LCodeGen::DoIn(LIn* instr) {
 }
 
 
+void LCodeGen::DoDeferredStackCheck(LStackCheck* instr) {
+  PushSafepointRegistersScope scope(this);
+  CallRuntimeFromDeferred(Runtime::kStackGuard, 0, instr);
+}
+
+
 void LCodeGen::DoStackCheck(LStackCheck* instr) {
-  // Perform stack overflow check.
-  Label done;
-  __ CompareRoot(rsp, Heap::kStackLimitRootIndex);
-  __ j(above_equal, &done, Label::kNear);
+  class DeferredStackCheck: public LDeferredCode {
+   public:
+    DeferredStackCheck(LCodeGen* codegen, LStackCheck* instr)
+        : LDeferredCode(codegen), instr_(instr) { }
+    virtual void Generate() { codegen()->DoDeferredStackCheck(instr_); }
+   private:
+    LStackCheck* instr_;
+  };
 
-  StackCheckStub stub;
-  CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
-  __ bind(&done);
+  if (instr->hydrogen()->is_function_entry()) {
+    // Perform stack overflow check.
+    Label done;
+    __ CompareRoot(rsp, Heap::kStackLimitRootIndex);
+    __ j(above_equal, &done, Label::kNear);
+    StackCheckStub stub;
+    CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
+    __ bind(&done);
+  } else {
+    ASSERT(instr->hydrogen()->is_backwards_branch());
+    // Perform stack overflow check if this goto needs it before jumping.
+    DeferredStackCheck* deferred_stack_check =
+        new DeferredStackCheck(this, instr);
+    __ CompareRoot(rsp, Heap::kStackLimitRootIndex);
+    __ j(below, deferred_stack_check->entry());
+    __ bind(instr->done_label());
+    deferred_stack_check->SetExit(instr->done_label());
+  }
 }