Consistently assume that arithmetic operations can overflow unless one can prove the opposite.

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 4396 matching lines @@
         HConstant::cast(right())->HasInteger32Value()) {
       int32_t value = HConstant::cast(right())->Integer32Value();
       return value != 0 && (IsPowerOf2(value) || IsPowerOf2(-value));
     }
 
     return false;
   }
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
+  virtual HValue* Canonicalize();
+
   DECLARE_CONCRETE_INSTRUCTION(Mod)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
   virtual Range* InferRange(Zone* zone);
 
  private:
   HMod(HValue* context, HValue* left, HValue* right)
       : HArithmeticBinaryOperation(context, left, right) {
     SetFlag(kCanBeDivByZero);
+    SetFlag(kCanOverflow);
   }
 };
 
 
 class HDiv: public HArithmeticBinaryOperation {
  public:
   static HInstruction* New(Zone* zone,
                            HValue* context,
                            HValue* left,
                            HValue* right);
 
   bool HasPowerOf2Divisor() {
     if (right()->IsConstant() &&
         HConstant::cast(right())->HasInteger32Value()) {
       int32_t value = HConstant::cast(right())->Integer32Value();
       return value != 0 && (IsPowerOf2(value) || IsPowerOf2(-value));
     }
 
     return false;
   }
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
+  virtual HValue* Canonicalize();
+
   DECLARE_CONCRETE_INSTRUCTION(Div)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
   virtual Range* InferRange(Zone* zone);
 
  private:
   HDiv(HValue* context, HValue* left, HValue* right)
       : HArithmeticBinaryOperation(context, left, right) {
@@ skipping 2006 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_