DummyUse if Representation::Tagged()+Type::Smi() to Representation::Smi()

src/x64/lithium-x64.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 1818 matching lines @@
   // building a stack frame.
   if (from.IsTagged()) {
     if (to.IsDouble()) {
       info()->MarkAsDeferredCalling();
       LOperand* value = UseRegister(instr->value());
       LNumberUntagD* res = new(zone()) LNumberUntagD(value);
       return AssignEnvironment(DefineAsRegister(res));
     } else if (to.IsSmi()) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
+      if (val->type().IsSmi()) {
+        return DefineSameAsFirst(new(zone()) LDummyUse(value));
+      }
       return AssignEnvironment(
           DefineSameAsFirst(new(zone()) LCheckSmiAndReturn(value)));
     } else {
       ASSERT(to.IsInteger32());
       LOperand* value = UseRegister(instr->value());
       if (instr->value()->type().IsSmi()) {
         LInstruction* result =
             DefineSameAsFirst(new(zone()) LSmiUntag(value, false));
         if (instr->value()->IsLoadKeyed()) {
           HLoadKeyed* load_keyed = HLoadKeyed::cast(instr->value());
@@ skipping 734 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64