Eliminate redundant smi checks

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 569d2954d7ea8cffd8911123cfa53d421d550c89..6b07ee6e66045e50733a09091aecb69a93e7bf9a 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -1710,10 +1710,8 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
     } else {
       ASSERT(to.IsInteger32());
       LOperand* value = UseRegisterAtStart(instr->value());
-      bool needs_check = !instr->value()->type().IsSmi();
-      LInstruction* res = NULL;
-      if (!needs_check) {
-        res = DefineAsRegister(new(zone()) LSmiUntag(value, needs_check));
+      if (instr->value()->IsValueTaggedSmi()) {
+        res = DefineAsRegister(new(zone()) LSmiUntag(value, false));
       } else {
         LOperand* temp1 = TempRegister();
         LOperand* temp2 = instr->CanTruncateToInt32() ? TempRegister()