[arm] Recognize SXTB, SXTH, UXTB and UXTH.

test/mjsunit/asm/zero-extend.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 stdlib = this;
+var buffer = new ArrayBuffer(64 * 1024);
+var foreign = {}
+
+
+var zext8 = (function Module(stdlib, foreign, heap) {
+  "use asm";
+  function zext8(i) {
+    i = i|0;
+    return i & 0xff;
+  }
+  return { zext8: zext8 };
+})(stdlib, foreign, buffer).zext8;
+
+assertEquals(0, zext8(0));
+assertEquals(0, zext8(0x100));
+assertEquals(0xff, zext8(-1));
+assertEquals(0xff, zext8(0xff));
+
+
+var zext16 = (function Module(stdlib, foreign, heap) {
+  "use asm";
+  function zext16(i) {
+    i = i|0;
+    return i & 0xffff;
+  }
+  return { zext16: zext16 };
+})(stdlib, foreign, buffer).zext16;
+
+assertEquals(0, zext16(0));
+assertEquals(0, zext16(0x10000));
+assertEquals(0xffff, zext16(-1));
+assertEquals(0xffff, zext16(0xffff));