A64: Tidy up register use in TaggedToI

src/a64/lithium-codegen-a64.cc

 // Copyright 2013 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 5350 matching lines @@
 
     virtual LInstruction* instr() { return instr_; }
    private:
     LTaggedToI* instr_;
   };
 
   Register input = ToRegister(instr->value());
   Register output = ToRegister(instr->result());
 
   if (instr->hydrogen()->value()->representation().IsSmi()) {
-    __ SmiUntag(input);
+    __ SmiUntag(output, input);
   } else {
     DeferredTaggedToI* deferred = new(zone()) DeferredTaggedToI(this, instr);
 
-    // TODO(jbramley): We can't use JumpIfNotSmi here because the tbz it uses
-    // doesn't always have enough range. Consider making a variant of it, or a
-    // TestIsSmi helper.
-    STATIC_ASSERT(kSmiTag == 0);
-    __ Tst(input, kSmiTagMask);
-    __ B(ne, deferred->entry());
-
+    __ JumpIfNotSmi(input, deferred->entry());
     __ SmiUntag(output, input);
     __ Bind(deferred->exit());
   }
 }
 
 
 void LCodeGen::DoThisFunction(LThisFunction* instr) {
   Register result = ToRegister(instr->result());
   __ Ldr(result, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
 }
@@ skipping 298 matching lines @@
   __ Bind(&out_of_object);
   __ Ldr(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
   // Index is equal to negated out of object property index plus 1.
   __ Sub(result, result, Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(result, FieldMemOperand(result,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ Bind(&done);
 }
 
 } }  // namespace v8::internal