Tweak register allocation for Math.round and do not use roundsd.

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index ff4c477bc7844d3919226e9873aef5eb892d687f..d66fa9c5b0e78152b23d36ed13417d9b530b00d1 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -132,6 +132,7 @@ class LCodeGen;
   V(MathFloorOfDiv)                             \
   V(MathMinMax)                                 \
   V(MathPowHalf)                                \
+  V(MathRound)                                  \
   V(ModI)                                       \
   V(MulI)                                       \
   V(NumberTagD)                                 \
@@ -700,6 +701,25 @@ class LMathPowHalf: public LTemplateInstruction<1, 2, 1> {
 };
 
 
+class LMathRound: public LTemplateInstruction<1, 2, 1> {
+ public:
+  LMathRound(LOperand* context, LOperand* value, LOperand* temp) {
+    inputs_[1] = context;
+    inputs_[0] = value;
+    temps_[0] = temp;
+  }
+
+  LOperand* context() { return inputs_[1]; }
+  LOperand* value() { return inputs_[0]; }
+  LOperand* temp() { return temps_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(MathRound, "math-round")
+  DECLARE_HYDROGEN_ACCESSOR(UnaryMathOperation)
+
+  virtual void PrintDataTo(StringStream* stream);
+};
+
+
 class LCmpObjectEqAndBranch: public LControlInstruction<2, 0> {
  public:
   LCmpObjectEqAndBranch(LOperand* left, LOperand* right) {