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

src/compiler/mips64/instruction-selector-mips64.cc

Index: src/compiler/mips64/instruction-selector-mips64.cc
diff --git a/src/compiler/mips64/instruction-selector-mips64.cc b/src/compiler/mips64/instruction-selector-mips64.cc
index b0841790621b02f81e2588ea6aecbad831ffcbc4..5ecd3217c3300f942557e9cde4fb9bb009a65af9 100644
--- a/src/compiler/mips64/instruction-selector-mips64.cc
+++ b/src/compiler/mips64/instruction-selector-mips64.cc
@@ -592,6 +592,11 @@ void InstructionSelector::VisitTruncateFloat64ToInt32(Node* node) {
 }
 
 
+void InstructionSelector::VisitRoundInt64ToFloat32(Node* node) {
+  VisitRR(this, kMips64CvtSL, node);
+}
+
+
 void InstructionSelector::VisitRoundInt64ToFloat64(Node* node) {
   VisitRR(this, kMips64CvtDL, node);
 }