[x64] Rearrange code for OOB integer loads.

test/mjsunit/compiler/regress-445858.js

 // 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.
 
-var foo = (function Module(stdlib, foreign, heap) {
+var foo = (function module(stdlib, foreign, heap) {
   "use asm";
-  var MEM16 = new stdlib.Int16Array(heap);
+  var MEM = new stdlib.Int8Array(heap);
   function foo(i) {
     i = i|0;
-    i = MEM16[i + 2147483650 >> 1]|0;
-    return i;
+    i[0] = i;
+    return MEM[i + 1 >> 0]|0;
   }
   return { foo: foo };
 })(this, {}, new ArrayBuffer(64 * 1024)).foo;
-
-foo(0);
+foo(-1);