Implemented the RoundInt64ToFloat32 TurboFan operator for x64, arm64, and mips64.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index b63a3d9954ef8743e22611cd60aa12c60cda5d68..81f8199dc567ed357d2f46ecd9deefa2deca14a8 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -817,6 +817,10 @@ class MacroAssembler: public Assembler {
   // xorpd to clear the dst register before cvtsi2sd to solve this issue.
   void Cvtlsi2sd(XMMRegister dst, Register src);
   void Cvtlsi2sd(XMMRegister dst, const Operand& src);
+
+  void Cvtqsi2ss(XMMRegister dst, Register src);
+  void Cvtqsi2ss(XMMRegister dst, const Operand& src);
+
   void Cvtqsi2sd(XMMRegister dst, Register src);
   void Cvtqsi2sd(XMMRegister dst, const Operand& src);