Correctly retain argument value when deopting from Math.round on x64.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 625b4f4ce5f57c7f450c9176aa6c322369e0eada..aad9597f1148c9396da9220feb0da202873ef123 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1133,8 +1133,9 @@ LInstruction* LChunkBuilder::DoMathFloor(HUnaryMathOperation* instr) {
 
 
 LInstruction* LChunkBuilder::DoMathRound(HUnaryMathOperation* instr) {
-  LOperand* input = UseRegisterAtStart(instr->value());
-  LMathRound* result = new(zone()) LMathRound(input);
+  LOperand* input = UseRegister(instr->value());
+  LOperand* temp = FixedTemp(xmm4);
+  LMathRound* result = new(zone()) LMathRound(input, temp);
   return AssignEnvironment(DefineAsRegister(result));
 }