Hydrogen object literals: always initialize in-object properties

test/mjsunit/regress/regress-crbug-500497.js

+// 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.
+
+// New space must be at max capacity to trigger pretenuring decision.
+// Flags: --allow-natives-syntax --verify-heap --max-semi-space-size=1
+
+var global = [];  // Used to keep some objects alive.
+
+function Ctor() {
+  var result = {a: {}, b: {}, c: {}, d: {}, e: {}, f: {}, g: {}};
+  return result;
+}
+
+for (var i = 0; i < 120; i++) {
+  // Make the "a" property long-lived, while everything else is short-lived.
+  global.push(Ctor().a);
+  (function FillNewSpace() { new Array(10000); })();
+}
+
+// The bad situation is only triggered if Ctor wasn't optimized too early.
+assertUnoptimized(Ctor);
+// Optimized code for Ctor will pretenure the "a" property, so it will have
+// three allocations:
+// #1 Allocate the "result" object in new-space.
+// #2 Allocate the object stored in the "a" property in old-space.
+// #3 Allocate the objects for the "b" through "g" properties in new-space.
+%OptimizeFunctionOnNextCall(Ctor);
+for (var i = 0; i < 10000; i++) {
+  // At least one of these calls will run out of new space. The bug is
+  // triggered when it is allocation #3 that triggers GC.
+  Ctor();
+}