[turbofan] Correctify lowering of Uint8ClampedArray buffer access.

test/mjsunit/compiler/regress-444508.js

Index: test/mjsunit/compiler/regress-444508.js
diff --git a/test/mjsunit/compiler/regress-444508.js b/test/mjsunit/compiler/regress-444508.js
new file mode 100644
index 0000000000000000000000000000000000000000..e7d51ae831fd0c20dcbac1e825ac3740bcb7e953
--- /dev/null
+++ b/test/mjsunit/compiler/regress-444508.js
@@ -0,0 +1,11 @@
+// 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.
+
+(function Module(stdlib, foreign, heap) {
+  "use asm";
+  // This is not valid asm.js, but should nevertheless work.
+  var MEM = new Uint8ClampedArray(heap);
+  function foo(i) { MEM[0] = 1; }
+  return {foo: foo};
+})(this, {}, new ArrayBuffer(64 * 1024)).foo();