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

src/compiler/arm64/instruction-selector-arm64.cc

Index: src/compiler/arm64/instruction-selector-arm64.cc
diff --git a/src/compiler/arm64/instruction-selector-arm64.cc b/src/compiler/arm64/instruction-selector-arm64.cc
index 169c8e988dcbc8e7c146b6b0e7e5adc829d694e7..b228f81be9a80e85cad1a925e89c45d2def172f2 100644
--- a/src/compiler/arm64/instruction-selector-arm64.cc
+++ b/src/compiler/arm64/instruction-selector-arm64.cc
@@ -1291,6 +1291,11 @@ void InstructionSelector::VisitTruncateInt64ToInt32(Node* node) {
 }
 
 
+void InstructionSelector::VisitRoundInt64ToFloat32(Node* node) {
+  VisitRR(this, kArm64Int64ToFloat32, node);
+}
+
+
 void InstructionSelector::VisitRoundInt64ToFloat64(Node* node) {
   VisitRR(this, kArm64Int64ToFloat64, node);
 }