Set kTruncatingToSmi for HChange only when To rep is Smi

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/218613002

Patch from Weiliang Lin <weiliang.lin@intel.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20385 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.cc

@@ -1561,6 +1561,7 @@ void HChange::PrintDataTo(StringStream* stream) {
   HUnaryOperation::PrintDataTo(stream);
   stream->Add(" %s to %s", from().Mnemonic(), to().Mnemonic());
 
+  if (CanTruncateToSmi()) stream->Add(" truncating-smi");
   if (CanTruncateToInt32()) stream->Add(" truncating-int32");
   if (CheckFlag(kBailoutOnMinusZero)) stream->Add(" -0?");
   if (CheckFlag(kAllowUndefinedAsNaN)) stream->Add(" allow-undefined-as-nan");

src/hydrogen-instructions.h

@@ -1263,6 +1263,7 @@ class HInstruction : public HValue {
     position_.set_operand_position(index, pos);
   }
 
+  bool CanTruncateToSmi() const { return CheckFlag(kTruncatingToSmi); }
   bool CanTruncateToInt32() const { return CheckFlag(kTruncatingToInt32); }
 
   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;
@@ -1733,7 +1734,7 @@ class HChange V8_FINAL : public HUnaryOperation {
     set_representation(to);
     SetFlag(kUseGVN);
     SetFlag(kCanOverflow);
-    if (is_truncating_to_smi) {
+    if (is_truncating_to_smi && to.IsSmi()) {
       SetFlag(kTruncatingToSmi);
       SetFlag(kTruncatingToInt32);
     }