Inline Math.fround in optimized code.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 7bc61c8d6493132fffad41a40b28bb081113a198..d552b31807ec3be5b164da1ce7fcd6bf158da68d 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3812,6 +3812,14 @@ void LCodeGen::DoMathRound(LMathRound* instr) {
 }
 
 
+void LCodeGen::DoMathFround(LMathFround* instr) {
+  XMMRegister input_reg = ToDoubleRegister(instr->value());
+  XMMRegister output_reg = ToDoubleRegister(instr->result());
+  __ cvtsd2ss(output_reg, input_reg);
+  __ cvtss2sd(output_reg, output_reg);
+}
+
+
 void LCodeGen::DoMathSqrt(LMathSqrt* instr) {
   XMMRegister output = ToDoubleRegister(instr->result());
   if (instr->value()->IsDoubleRegister()) {