[turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

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

 // Copyright 2014 the V8 project authors. All rights reserved. Use of this
 // source code is governed by a BSD-style license that can be found in the
 // LICENSE file.
 
 // TODO(jochen): Remove this after the setting is turned on globally.
 #define V8_IMMINENT_DEPRECATION_WARNINGS
 
 #include <cmath>
 #include <functional>
 #include <limits>
@@ skipping 5468 matching lines @@
       &output, kMachInt64,
       m.BitcastFloat64ToInt64(m.LoadFromPointer(&input, kMachFloat64)));
   m.Return(m.Int32Constant(11));
   FOR_FLOAT64_INPUTS(i) {
     input = *i;
     CHECK_EQ(11, m.Call());
     double expected = bit_cast<int64_t>(input);
     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
 
 
 TEST(RunBitcastFloat32ToInt32) {
   float input = 32.25;
   RawMachineAssemblerTester<int32_t> m;
   m.Return(m.BitcastFloat32ToInt32(m.LoadFromPointer(&input, kMachFloat32)));
   FOR_FLOAT32_INPUTS(i) {
     input = *i;
     int32_t expected = bit_cast<int32_t>(input);
@@ skipping 61 matching lines @@
       c->CalleeSavedRegisters(),                         // callee saved
       c->CalleeSavedFPRegisters(),                       // callee saved FP
       CallDescriptor::kNoFlags,                          // flags
       "c-call-as-code");
   Node* call = r.AddNode(r.common()->Call(desc), phi);
   r.Return(call);
 
   CHECK_EQ(33, r.Call(1));
   CHECK_EQ(44, r.Call(0));
 }