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

src/ia32/macro-assembler-ia32.h

Index: src/ia32/macro-assembler-ia32.h
diff --git a/src/ia32/macro-assembler-ia32.h b/src/ia32/macro-assembler-ia32.h
index 68df2556a7ef7acf4b4c96aa776cdad37a5f6f57..a5018b8ad946ff7a1d4c81981b5570a270662ed5 100644
--- a/src/ia32/macro-assembler-ia32.h
+++ b/src/ia32/macro-assembler-ia32.h
@@ -343,6 +343,8 @@ class MacroAssembler: public Assembler {
   // xorps to clear the dst register before cvtsi2sd to solve this issue.
   void Cvtsi2sd(XMMRegister dst, Register src) { Cvtsi2sd(dst, Operand(src)); }
   void Cvtsi2sd(XMMRegister dst, const Operand& src);
+  void Cvtsi2ss(XMMRegister dst, Register src) { Cvtsi2ss(dst, Operand(src)); }
+  void Cvtsi2ss(XMMRegister dst, const Operand& src);
 
   // Support for constant splitting.
   bool IsUnsafeImmediate(const Immediate& x);