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

test/cctest/compiler/test-run-machops.cc

Index: test/cctest/compiler/test-run-machops.cc
diff --git a/test/cctest/compiler/test-run-machops.cc b/test/cctest/compiler/test-run-machops.cc
index b7c978a747d76e8c6639b502e31f64a5164be84d..34231726137cd1159b5063d3a8ea5a8406bee11f 100644
--- a/test/cctest/compiler/test-run-machops.cc
+++ b/test/cctest/compiler/test-run-machops.cc
@@ -5348,6 +5348,13 @@ TEST(RunBitcastFloat64ToInt64) {
 }
 
 
+TEST(RunRoundInt64ToFloat32) {
+  BufferedRawMachineAssemblerTester<float> m(kMachInt64);
+  m.Return(m.RoundInt64ToFloat32(m.Parameter(0)));
+  FOR_INT64_INPUTS(i) { CHECK_EQ(static_cast<float>(*i), m.Call(*i)); }
+}
+
+
 TEST(RunRoundInt64ToFloat64) {
   BufferedRawMachineAssemblerTester<double> m(kMachInt64);
   m.Return(m.RoundInt64ToFloat64(m.Parameter(0)));