Fix fast array literals to ignore prototype chain.

test/mjsunit/regress/regress-123512.js

+// Copyright 2012 the V8 project authors. All rights reserved.
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+
+// Flags: --allow-natives-syntax
+
+// Test that boilerplate objects for array literals with non-constant
+// elements (which will contain the hole at non-constant positions) will
+// not cause prototype chain lookups when generating optimized code.
+
+function f(x) {
+  return [x][0];
+}
+
+// Test data element on prototype.
+Object.prototype[0] = 23;
+assertSame(1, f(1));
+assertSame(2, f(2));
+%OptimizeFunctionOnNextCall(f);
+assertSame(3, f(3));
+%DeoptimizeFunction(f);
+
+// Test accessor element on prototype.
+Object.prototype.__defineGetter__(0, function() { throw Error(); });
+assertSame(4, f(4));
+assertSame(5, f(5));
+%OptimizeFunctionOnNextCall(f);
+assertSame(6, f(6));
+%DeoptimizeFunction(f);

[Erik Corry, 2012/04/17 10:35:37]

Can we test the same for object literals as we do for Array literals?

[Michael Starzinger, 2012/04/17 10:59:52]

Done (for both properties and elements on object literals).