Port string keyed load IC improvements (r4444) to x64.

test/mjsunit/string-index.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 177 matching lines @@
 
 var keys = [0, '1', 2, 3.0, -1, 10];
 var str = 'abcd', arr = ['a', 'b', 'c', 'd', undefined, undefined];
 for (var i = 0; i < 300; ++i) {
   var index = Math.floor(i / 50);
   var key = keys[index];
   var expected = arr[index];
   var actual = str[key];
   assertEquals(expected, actual);
 }
+
+// Test heap number case.
+var keys = [0, Math.floor(2) * 0.5];
+var str = 'ab', arr = ['a', 'b'];
+for (var i = 0; i < 100; ++i) {
+  var index = Math.floor(i / 50);
+  var key = keys[index];
+  var expected = arr[index];
+  var actual = str[key];
+  assertEquals(expected, actual);
+}
+
+// Test out of range case.
+var keys = [0, -1];
+var str = 'ab', arr = ['a', undefined];
+for (var i = 0; i < 100; ++i) {
+  var index = Math.floor(i / 50);
+  var key = keys[index];
+  var expected = arr[index];
+  var actual = str[key];
+  assertEquals(expected, actual);
+}
+
+var keys = [0, 10];
+var str = 'ab', arr = ['a', undefined];
+for (var i = 0; i < 100; ++i) {
+  var index = Math.floor(i / 50);
+  var key = keys[index];
+  var expected = arr[index];
+  var actual = str[key];
+  assertEquals(expected, actual);
+}