[turbofan] Add proper conversion operators for int32<->int64.

test/compiler-unittests/x64/instruction-selector-x64-unittest.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.
+
+#include "test/compiler-unittests/instruction-selector-unittest.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// -----------------------------------------------------------------------------
+// Conversions.
+
+
+TEST_F(InstructionSelectorTest, ChangeInt32ToInt64WithParameter) {
+  StreamBuilder m(this, kMachInt64, kMachInt32);
+  m.Return(m.ChangeInt32ToInt64(m.Parameter(0)));
+  Stream s = m.Build();
+  ASSERT_EQ(1U, s.size());
+  EXPECT_EQ(kX64Movsxlq, s[0]->arch_opcode());
+}
+
+
+TEST_F(InstructionSelectorTest, ChangeUint32ToUint64WithParameter) {
+  StreamBuilder m(this, kMachUint64, kMachUint32);
+  m.Return(m.ChangeUint32ToUint64(m.Parameter(0)));
+  Stream s = m.Build();
+  ASSERT_EQ(1U, s.size());
+  EXPECT_EQ(kX64Movl, s[0]->arch_opcode());
+}
+
+
+TEST_F(InstructionSelectorTest, TruncateInt64ToInt32WithParameter) {
+  StreamBuilder m(this, kMachInt32, kMachInt64);
+  m.Return(m.TruncateInt64ToInt32(m.Parameter(0)));
+  Stream s = m.Build();
+  ASSERT_EQ(1U, s.size());
+  EXPECT_EQ(kX64Movl, s[0]->arch_opcode());
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8