[turbofan] Implement rounding of floats on x64 and ia32 without sse4.1.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 5222bc9c718164d84857c6fa613fc5de4e7e52fe..529a9ad425baf58362e966b9956130218529a6e1 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -581,6 +581,12 @@ void MacroAssembler::DebugBreak() {
 }
 
 
+void MacroAssembler::Cvtsi2ss(XMMRegister dst, const Operand& src) {
+  xorps(dst, dst);
+  cvtsi2ss(dst, src);
+}
+
+
 void MacroAssembler::Cvtsi2sd(XMMRegister dst, const Operand& src) {
   xorps(dst, dst);
   cvtsi2sd(dst, src);