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

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 2e360c5d18521f56717c5bc18db858ee13609605..a290628d8f65dd168c66475197ec3466f4f413f7 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -4414,6 +4414,8 @@ class HMod: public HArithmeticBinaryOperation {
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
+  virtual HValue* Canonicalize();
+
   DECLARE_CONCRETE_INSTRUCTION(Mod)
 
  protected:
@@ -4425,6 +4427,7 @@ class HMod: public HArithmeticBinaryOperation {
   HMod(HValue* context, HValue* left, HValue* right)
       : HArithmeticBinaryOperation(context, left, right) {
     SetFlag(kCanBeDivByZero);
+    SetFlag(kCanOverflow);
   }
 };
 
@@ -4448,6 +4451,8 @@ class HDiv: public HArithmeticBinaryOperation {
 
   virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
 
+  virtual HValue* Canonicalize();
+
   DECLARE_CONCRETE_INSTRUCTION(Div)
 
  protected: