Change the handling of stack check on backward branches

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index f2ca730b404d6c62585b7de1905cec0d4e4a79e5..c655e8f09cd3798d948949240ea1bc9de2ded7df 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -895,24 +895,15 @@ class HDeoptimize: public HControlInstruction {
 
 class HGoto: public HTemplateControlInstruction<1, 0> {
  public:
-  explicit HGoto(HBasicBlock* target)
-      : include_stack_check_(false) {
+  explicit HGoto(HBasicBlock* target) {
         SetSuccessorAt(0, target);
       }
 
-  void set_include_stack_check(bool include_stack_check) {
-    include_stack_check_ = include_stack_check;
-  }
-  bool include_stack_check() const { return include_stack_check_; }
-
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::None();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(Goto)
-
- private:
-  bool include_stack_check_;
 };
 
 
@@ -1257,13 +1248,31 @@ class HSimulate: public HInstruction {
 
 class HStackCheck: public HTemplateInstruction<0> {
  public:
-  HStackCheck() { }
+  enum Type {
+    kFunctionEntry,
+    kBackwardsBranch
+  };
+
+  explicit HStackCheck(Type type) : type_(type), eliminated_(false) { }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::None();
   }
 
+  bool is_function_entry() { return type_ == kFunctionEntry; }
+  bool is_backwards_branch() { return type_ == kBackwardsBranch; }
+
+  void set_eliminated(bool eliminated) {
+    ASSERT(is_backwards_branch());
+    eliminated_ = eliminated;
+  }
+  bool is_eliminated() const { return eliminated_; }
+
   DECLARE_CONCRETE_INSTRUCTION(StackCheck)
+
+ private:
+  Type type_;
+  bool eliminated_;
 };