Change the handling of stack check on backward branches

src/hydrogen-instructions.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 877 matching lines @@
     values_[index] = value;
   }
 
  private:
   ZoneList<HValue*> values_;
 };
 
 
 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_;
 };
 
 
 class HUnaryControlInstruction: public HTemplateControlInstruction<2, 1> {
  public:
   HUnaryControlInstruction(HValue* value,
                            HBasicBlock* true_target,
                            HBasicBlock* false_target) {
     SetOperandAt(0, value);
     SetSuccessorAt(0, true_target);
@@ skipping 324 matching lines @@
   }
   int ast_id_;
   int pop_count_;
   ZoneList<HValue*> values_;
   ZoneList<int> assigned_indexes_;
 };
 
 
 class HStackCheck: public HTemplateInstruction<0> {
  public:
-  HStackCheck() { }
+  enum Type {
+    kFunctionEntry,
+    kBackwardsBranch
+  };
+
+  explicit HStackCheck(Type type) : type_(type) { }
 
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::None();
   }
 
+  void Eliminate() {
+    // The stack check eliminator might try to eliminate the same stack
+    // check instruction multiple times.
+    if (IsLinked()) {
+      DeleteFromGraph();
+    }
+  }
+
+  bool is_function_entry() { return type_ == kFunctionEntry; }
+  bool is_backwards_branch() { return type_ == kBackwardsBranch; }
+
   DECLARE_CONCRETE_INSTRUCTION(StackCheck)
+
+ private:
+  Type type_;
 };
 
 
 class HEnterInlined: public HTemplateInstruction<0> {
  public:
   HEnterInlined(Handle<JSFunction> closure,
                 FunctionLiteral* function,
                 CallKind call_kind)
       : closure_(closure),
         function_(function),
@@ skipping 2827 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(In)
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_