ARM64: do not optimize away shift if its result is used as both left and right

test/mjsunit/regress/regress-491049.js

Index: test/mjsunit/regress/regress-491049.js
diff --git a/test/mjsunit/regress/regress-filter-contexts.js b/test/mjsunit/regress/regress-491049.js
similarity index 66%
copy from test/mjsunit/regress/regress-filter-contexts.js
copy to test/mjsunit/regress/regress-491049.js
index d2abe0032548428324afd6675a7031bf53a5e56e..c010b0911dcd5f700406a5950d05e16055979857 100644
--- a/test/mjsunit/regress/regress-filter-contexts.js
+++ b/test/mjsunit/regress/regress-491049.js
@@ -2,13 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+function f(a) {
+  return (a >>> 12) + (a >>> 2);
+}
 
-function f() { return f.x; }
-f.__proto__ = null;
-f.prototype = "";
-
-f();
 f();
+
 %OptimizeFunctionOnNextCall(f);
+
 f();