MIPS: Optimize Integer32ToSmi.

src/mips/lithium-codegen-mips.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 4615 matching lines @@
   }
   __ cvt_d_w(ToDoubleRegister(output), single_scratch);
 }
 
 
 void LCodeGen::DoInteger32ToSmi(LInteger32ToSmi* instr) {
   LOperand* input = instr->value();
   LOperand* output = instr->result();
   Register scratch = scratch0();
 
-  __ SmiTagCheckOverflow(ToRegister(output), ToRegister(input), scratch);
+  ASSERT(output->IsRegister());
   if (!instr->hydrogen()->value()->HasRange() ||
       !instr->hydrogen()->value()->range()->IsInSmiRange()) {
+    __ SmiTagCheckOverflow(ToRegister(output), ToRegister(input), scratch);
     DeoptimizeIf(lt, instr->environment(), scratch, Operand(zero_reg));
+  } else {
+    __ SmiTag(ToRegister(output), ToRegister(input));
   }
 }
 
 
 void LCodeGen::DoUint32ToDouble(LUint32ToDouble* instr) {
   LOperand* input = instr->value();
   LOperand* output = instr->result();
 
   FPURegister dbl_scratch = double_scratch0();
   __ mtc1(ToRegister(input), dbl_scratch);
@@ skipping 1217 matching lines @@
   __ Subu(scratch, result, scratch);
   __ lw(result, FieldMemOperand(scratch,
                                 FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal