On x64 use 32bit idiv when possible instead of 64bit one.

runtime/vm/assembler_x64_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/os.h"
 #include "vm/unit_test.h"
@@ skipping 497 matching lines @@
   __ ret();
 }
 
 
 ASSEMBLER_TEST_RUN(MoveExtend, test) {
   typedef int (*MoveExtend)();
   EXPECT_EQ(0xff - 1 + 0xffff, reinterpret_cast<MoveExtend>(test->entry())());
 }
 
 
+ASSEMBLER_TEST_GENERATE(MoveExtend32, assembler) {
+  __ movq(RDX, Immediate(0xffffffff));
+  __ movsxl(RDX, RDX);
+  __ movq(RAX, Immediate(0x7fffffff));
+  __ movsxl(RAX, RAX);
+  __ addq(RAX, RDX);
+  __ ret();
+}
+
+
+ASSEMBLER_TEST_RUN(MoveExtend32, test) {
+  typedef intptr_t (*MoveExtend)();
+  EXPECT_EQ(0x7ffffffe, reinterpret_cast<MoveExtend>(test->entry())());
+}
+
+
 ASSEMBLER_TEST_GENERATE(MoveExtendMemory, assembler) {
   __ movq(RDX, Immediate(0x123456781234ffff));
 
   __ pushq(RDX);
   __ movzxb(RAX, Address(RSP, 0));  // RAX = 0xff
   __ movsxw(R8, Address(RSP, 0));   // R8 = -1
   __ movzxw(RCX, Address(RSP, 0));  // RCX = 0xffff
   __ addq(RSP, Immediate(kWordSize));
 
   __ addq(R8, RCX);
@@ skipping 1725 matching lines @@
   EXPECT_EQ(0, res);
   res = reinterpret_cast<ExtractSignBits>(test->entry())(-1.0);
   EXPECT_EQ(1, res);
   res = reinterpret_cast<ExtractSignBits>(test->entry())(-0.0);
   EXPECT_EQ(1, res);
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64