Mark maps as unstable if their instances potentially transition away.

test/mjsunit/regress/regress-omit-checks.js

 // Copyright 2013 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
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --allow-natives-syntax
 
-function ar() {
-  var r = undefined;
-  var f = 1;
-  while (f--) {
-    r = (typeof r === 'undefined') ? 0.1 : r;
-  };
-  return (r - r);
+var a = {x:1};
+var a_deprecate = {x:1};
+a_deprecate.x = 1.5;
+function create() {
+  return {__proto__:a, y:1};
+}
+var b1 = create();
+var b2 = create();
+var b3 = create();
+var b4 = create();
+
+function set(b) {
+  b.x = 5;
+  b.z = 10;
 }
 
-assertEquals(0, ar());
-assertEquals(0, ar());
-%OptimizeFunctionOnNextCall(ar);
-assertEquals(0, ar());
-
-function ar2() {
-  var r = undefined;
-  var f = 1;
-  while (f--) {
-    r = r === undefined ? 0.1 : r;
-  };
-  return (r - r);
-}
-
-assertEquals(0, ar2());
-assertEquals(0, ar2());
-%OptimizeFunctionOnNextCall(ar2);
-assertEquals(0, ar2());
+set(b1);
+set(b2);
+%OptimizeFunctionOnNextCall(set);
+set(b3);
+var called = false;
+a.x = 1.5;
+Object.defineProperty(a, "z", {set:function(v) { called = true; }});
+set(b4);
+assertTrue(called);
+assertEquals(undefined, b4.z);