Add more tests to mul-exhaustive for constant left/right parameters.

test/mjsunit/smi-negative-zero.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
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@@ skipping 91 matching lines @@
 
 // This tests against a singleton -0.0 object being overwritten.gc
 x = 0;
 z = 3044;
 
 function foo(x) {
   var y = -x + z;
   return -x;
 }
 
-assertEquals(0, foo(x));
-assertEquals(0, foo(x));
+assertEquals(-0, foo(x));
+assertEquals(-0, foo(x));