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

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index 5c021270b83682f64180b44c38f59e853c61d990..09315ccafc59717f7abf60e29b39d3d542b3a7b3 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -2107,6 +2107,11 @@ Type* Typer::Visitor::TypeTruncateInt64ToInt32(Node* node) {
 }
 
 
+Type* Typer::Visitor::TypeRoundInt64ToFloat32(Node* node) {
+  return Type::Intersect(Type::PlainNumber(), Type::UntaggedFloat32(), zone());
+}
+
+
 Type* Typer::Visitor::TypeRoundInt64ToFloat64(Node* node) {
   return Type::Intersect(Type::PlainNumber(), Type::UntaggedFloat64(), zone());
 }