[Turbofan]: Eliminate the check for -0 if it's not possible/observable.

src/compiler/representation-change.cc

Index: src/compiler/representation-change.cc
diff --git a/src/compiler/representation-change.cc b/src/compiler/representation-change.cc
index 945cb1825dda2eeebdb840eadd33f30838ec881e..ba744de7b8b72e9bfd921b8eff1be86b705b4f06 100644
--- a/src/compiler/representation-change.cc
+++ b/src/compiler/representation-change.cc
@@ -628,7 +628,10 @@ const Operator* RepresentationChanger::Int32OverflowOperatorFor(
     case IrOpcode::kSpeculativeNumberModulus:
       return simplified()->CheckedInt32Mod();
     case IrOpcode::kSpeculativeNumberMultiply:
-      return simplified()->CheckedInt32Mul();
+      // Shouldn't get here.
+      DCHECK(false);
+      return simplified()->CheckedInt32Mul(
+          CheckForMinusZeroMode::kCheckForMinusZero);

[Jarin, 2016/07/17 16:37:47]

Just remove this case.

[mvstanton, 2016/07/18 08:48:58]

Done.

     default:
       UNREACHABLE();
       return nullptr;