Eliminate overflow check after integer add and sub if result is truncated to int32.

src/hydrogen-instructions.h

 // Copyright 2012 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 627 matching lines @@
   int UseCount() const;
 
   // Mark this HValue as dead and to be removed from other HValues' use lists.
   void Kill();
 
   int flags() const { return flags_; }
   void SetFlag(Flag f) { flags_ |= (1 << f); }
   void ClearFlag(Flag f) { flags_ &= ~(1 << f); }
   bool CheckFlag(Flag f) const { return (flags_ & (1 << f)) != 0; }
 
+  // Returns true if the flag specified is set for all uses, false otherwise.
+  bool CheckUsesForFlag(Flag f);
+
   GVNFlagSet gvn_flags() const { return gvn_flags_; }
   void SetGVNFlag(GVNFlag f) { gvn_flags_.Add(f); }
   void ClearGVNFlag(GVNFlag f) { gvn_flags_.Remove(f); }
   bool CheckGVNFlag(GVNFlag f) const { return gvn_flags_.Contains(f); }
   void SetAllSideEffects() { gvn_flags_.Add(AllSideEffectsFlagSet()); }
   void ClearAllSideEffects() {
     gvn_flags_.Remove(AllSideEffectsFlagSet());
   }
   bool HasSideEffects() const {
     return gvn_flags_.ContainsAnyOf(AllSideEffectsFlagSet());
@@ skipping 159 matching lines @@
 
   bool IsLinked() const { return block() != NULL; }
   void Unlink();
   void InsertBefore(HInstruction* next);
   void InsertAfter(HInstruction* previous);
 
   int position() const { return position_; }
   bool has_position() const { return position_ != RelocInfo::kNoPosition; }
   void set_position(int position) { position_ = position; }
 
+  bool CanTruncateToInt32() const { return CheckFlag(kTruncatingToInt32); }
+
   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;
 
 #ifdef DEBUG
   virtual void Verify();
 #endif
 
   virtual bool IsCall() { return false; }
 
   DECLARE_ABSTRACT_INSTRUCTION(Instruction)
 
@@ skipping 277 matching lines @@
 class HUnaryOperation: public HTemplateInstruction<1> {
  public:
   explicit HUnaryOperation(HValue* value) {
     SetOperandAt(0, value);
   }
 
   static HUnaryOperation* cast(HValue* value) {
     return reinterpret_cast<HUnaryOperation*>(value);
   }
 
-  virtual bool CanTruncateToInt32() const {
-    return CheckFlag(kTruncatingToInt32);
-  }
-
   HValue* value() { return OperandAt(0); }
   virtual void PrintDataTo(StringStream* stream);
 };
 
 
 class HThrow: public HTemplateInstruction<2> {
  public:
   HThrow(HValue* context, HValue* value) {
     SetOperandAt(0, context);
     SetOperandAt(1, value);
@@ skipping 103 matching lines @@
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
 class HToInt32: public HUnaryOperation {
  public:
   explicit HToInt32(HValue* value)
       : HUnaryOperation(value) {
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
+    SetFlag(kTruncatingToInt32);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
-  virtual bool CanTruncateToInt32() const {
-    return true;
-  }
-
   virtual HValue* Canonicalize() {
     if (value()->representation().IsInteger32()) {
       return value();
     } else {
       return this;
     }
   }
 
   DECLARE_CONCRETE_INSTRUCTION(ToInt32)
 
@@ skipping 1876 matching lines @@
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
   static HInstruction* NewHAdd(Zone* zone,
                                HValue* context,
                                HValue* left,
                                HValue* right);
 
   virtual HType CalculateInferredType();
 
+  virtual HValue* Canonicalize();
+
   DECLARE_CONCRETE_INSTRUCTION(Add)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
   virtual Range* InferRange(Zone* zone);
 };
 
 
 class HSub: public HArithmeticBinaryOperation {
  public:
   HSub(HValue* context, HValue* left, HValue* right)
       : HArithmeticBinaryOperation(context, left, right) {
     SetFlag(kCanOverflow);
   }
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
+  virtual HValue* Canonicalize();
+
   static HInstruction* NewHSub(Zone* zone,
                               HValue* context,
                               HValue* left,
                               HValue* right);
 
   DECLARE_CONCRETE_INSTRUCTION(Sub)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
@@ skipping 65 matching lines @@
 class HDiv: public HArithmeticBinaryOperation {
  public:
   HDiv(HValue* context, HValue* left, HValue* right)
       : HArithmeticBinaryOperation(context, left, right) {
     SetFlag(kCanBeDivByZero);
     SetFlag(kCanOverflow);
   }
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
-
   static HInstruction* NewHDiv(Zone* zone,
                                HValue* context,
                                HValue* left,
                                HValue* right);
 
   DECLARE_CONCRETE_INSTRUCTION(Div)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
@@ skipping 1532 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(LoadFieldByIndex);
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_