ARM: Optimize Integer32ToSmi

Optimize register constraints and code generated for Integer32ToSmi Lithium
instruction.

TEST=none
BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/88383002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18084 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -2031,8 +2031,8 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
       LInstruction* result = val->CheckFlag(HInstruction::kUint32)
-          ? DefineSameAsFirst(new(zone()) LUint32ToSmi(value))
-          : DefineSameAsFirst(new(zone()) LInteger32ToSmi(value));
+          ? DefineAsRegister(new(zone()) LUint32ToSmi(value))
+          : DefineAsRegister(new(zone()) LInteger32ToSmi(value));
       if (val->HasRange() && val->range()->IsInSmiRange()) {
         return result;
       }

src/arm/lithium-codegen-arm.cc

@@ -4695,10 +4695,13 @@ void LCodeGen::DoInteger32ToDouble(LInteger32ToDouble* instr) {
 void LCodeGen::DoInteger32ToSmi(LInteger32ToSmi* instr) {
   LOperand* input = instr->value();
   LOperand* output = instr->result();
-  __ SmiTag(ToRegister(output), ToRegister(input), SetCC);
+  ASSERT(output->IsRegister());
   if (!instr->hydrogen()->value()->HasRange() ||
       !instr->hydrogen()->value()->range()->IsInSmiRange()) {
+    __ SmiTag(ToRegister(output), ToRegister(input), SetCC);
     DeoptimizeIf(vs, instr->environment());
+  } else {
+    __ SmiTag(ToRegister(output), ToRegister(input));
   }
 }