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deps/v8/test/mjsunit/keyed-load-hole-to-undefined.js

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+// Copyright 2015 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 --turbofan --no-always-turbofan
+
+// is specified because the test corrupts the "pristine"
+// array prototype chain by storing an element, and this is tracked
+// per-isolate. A subsequent stress run would send the load generic,
+// and no more deoptimizations of foo would occur.
+
+function foo(a, i) { return a[i]; }
+
+%PrepareFunctionForOptimization(foo);
+var a = ['one', , 'three'];
+foo(a, 0);
+foo(a, 0);
+foo(a, 0);
+%OptimizeFunctionOnNextCall(foo);
+assertEquals(undefined, foo(a, 1));
+assertOptimized(foo);
+
+// Whereas if we disrupt the prototype chain...
+Array.prototype[1] = 'cow';
+assertUnoptimized(foo);
+assertEquals('cow', foo(a, 1));