[ia32] Fix invalid DCHECK on cmpw with immediate.

test/mjsunit/regress/regress-6063.js

Index: test/mjsunit/regress/regress-6063.js
diff --git a/test/mjsunit/regress/regress-6063.js b/test/mjsunit/regress/regress-6063.js
new file mode 100644
index 0000000000000000000000000000000000000000..4a0d16824a5c544762c896b18a8eb426bf5617be
--- /dev/null
+++ b/test/mjsunit/regress/regress-6063.js
@@ -0,0 +1,17 @@
+// Copyright 2017 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.
+
+// Flags: --allow-natives-syntax
+
+var U16 = new Uint16Array(2);
+U16[0] = 0xffff;
+
+function foo(a, i) {
+  return U16[0] === 0xffff;
+}
+
+assertTrue(foo());
+assertTrue(foo());
+%OptimizeFunctionOnNextCall(foo);
+assertTrue(foo());