MIPS: Optimize NumberTagU

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 1a99bb9096943d4027c4dda091abcf0932fb30eb..4b161d6b83742ed8e62c4a832407352d9693d83b 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1940,7 +1940,7 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
       LOperand* value = UseRegisterAtStart(val);
       if (val->CheckFlag(HInstruction::kUint32)) {
         LNumberTagU* result = new(zone()) LNumberTagU(value);
-        return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
+        return AssignEnvironment(AssignPointerMap(DefineAsRegister(result)));
       } else if (val->HasRange() && val->range()->IsInSmiRange()) {
         return DefineAsRegister(new(zone()) LSmiTag(value));
       } else {