Eliminate redundant smi checks

src/arm/lithium-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1692 matching lines @@
   Representation from = instr->from();
   Representation to = instr->to();
   if (from.IsTagged()) {
     if (to.IsDouble()) {
       LOperand* value = UseRegister(instr->value());
       LNumberUntagD* res = new(zone()) LNumberUntagD(value);
       return AssignEnvironment(DefineAsRegister(res));
     } 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()
                                                       : NULL;
         LOperand* temp3 = instr->CanTruncateToInt32() ? FixedTemp(d11)
                                                       : NULL;
         res = DefineSameAsFirst(new(zone()) LTaggedToI(value,
                                                        temp1,
                                                        temp2,
                                                        temp3));
@@ skipping 668 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseRegister(instr->index());
   return DefineAsRegister(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal