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

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 81059ec80f0ea7ca76827a7cc2d954e195e6971d..c8f99a11a64144fa38adb77b470a960c4619b047 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -3165,6 +3165,28 @@ void Assembler::cvtlsi2ss(XMMRegister dst, Register src) {
 }
 
 
+void Assembler::cvtqsi2ss(XMMRegister dst, const Operand& src) {
+  DCHECK(!IsEnabled(AVX));
+  EnsureSpace ensure_space(this);
+  emit(0xF3);
+  emit_rex_64(dst, src);
+  emit(0x0F);
+  emit(0x2A);
+  emit_sse_operand(dst, src);
+}
+
+
+void Assembler::cvtqsi2ss(XMMRegister dst, Register src) {
+  DCHECK(!IsEnabled(AVX));
+  EnsureSpace ensure_space(this);
+  emit(0xF3);
+  emit_rex_64(dst, src);
+  emit(0x0F);
+  emit(0x2A);
+  emit_sse_operand(dst, src);
+}
+
+
 void Assembler::cvtqsi2sd(XMMRegister dst, const Operand& src) {
   DCHECK(!IsEnabled(AVX));
   EnsureSpace ensure_space(this);