[turbofan] Add the RoundInt32ToFloat32 operator 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 11a3582cbb5d07e022ad09ae40cb08e3595abccb..76f5654c52d572d0a4d67d88768e50721533ec72 100644
--- a/test/cctest/compiler/test-run-machops.cc
+++ b/test/cctest/compiler/test-run-machops.cc
@@ -6001,6 +6001,13 @@ TEST(RunBitcastFloat32ToInt32) {
 }
 
 
+TEST(RunRoundInt32ToFloat32) {
+  BufferedRawMachineAssemblerTester<float> m(MachineType::Int32());
+  m.Return(m.RoundInt32ToFloat32(m.Parameter(0)));
+  FOR_INT32_INPUTS(i) { CHECK_EQ(static_cast<float>(*i), m.Call(*i)); }
+}
+
+
 TEST(RunBitcastInt32ToFloat32) {
   int32_t input = 1;
   float output = 0.0;