src/v8/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);

// Test the same on boilerplate objects for object literals that contain
// both non-constant properties and non-constant elements.

function g(x, y) {
  var o = { foo:x, 0:y };
  return o.foo + o[0];
}

// Test data property and element on prototype.
Object.prototype[0] = 23;
Object.prototype.foo = 42;
assertSame(3, g(1, 2));
assertSame(5, g(2, 3));
%OptimizeFunctionOnNextCall(g);
assertSame(7, g(3, 4));
%DeoptimizeFunction(g);

// Test accessor property and element on prototype.
Object.prototype.__defineGetter__(0, function() { throw Error(); });
Object.prototype.__defineGetter__('foo', function() { throw Error(); });
assertSame(3, g(1, 2));
assertSame(5, g(2, 3));
%OptimizeFunctionOnNextCall(g);
assertSame(7, g(3, 4));
%DeoptimizeFunction(g);