[turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

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 368f5e3687000db43c51966bf6817aa3a4214815..7cff4cef9e9bf8bb4bafd7df0a049185e3006f46 100644
--- a/test/cctest/compiler/test-run-machops.cc
+++ b/test/cctest/compiler/test-run-machops.cc
@@ -5486,6 +5486,15 @@ TEST(RunBitcastFloat64ToInt64) {
     CHECK_EQ(expected, output);
   }
 }
+
+
+TEST(RunChangeInt64ToFloat64) {
+  BufferedRawMachineAssemblerTester<double> m(kMachInt64);
+  m.Return(m.ChangeInt64ToFloat64(m.Parameter(0)));
+  FOR_INT64_INPUTS(i) { CHECK_EQ(static_cast<double>(*i), m.Call(*i)); }
+}
+
+
 #endif