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[turbofan] Fix lowering of Function.prototype accesses.

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This fixes a corner case where the "instance prototype" diverges from
the "non-instance prototype" that we store on the initial map of a
constructor function.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-703610
BUG=chromium:703610

Change-Id: I30a19ae621e10b512215ffb191ce00d030941440
Reviewed-on: https://chromium-review.googlesource.com/458396
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44008}
This commit is contained in:
Michael Starzinger 2017-03-22 10:09:21 +01:00 committed by Commit Bot
parent a6e6160e48
commit 37b9d653c2
2 changed files with 17 additions and 1 deletions
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2
src/compiler/js-native-context-specialization.cc
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@ -846,7 +846,7 @@ Reduction JSNativeContextSpecialization::ReduceJSLoadNamed(Node* node) {
// continue unless deoptimization is enabled.
Handle<Map> initial_map(function->initial_map(), isolate());
dependencies()->AssumeInitialMapCantChange(initial_map);
Handle<Object> prototype(initial_map->prototype(), isolate());
Handle<Object> prototype(function->prototype(), isolate());
Node* value = jsgraph()->Constant(prototype);
ReplaceWithValue(node, value);
return Replace(value);

16
test/mjsunit/regress/regress-crbug-703610.js Normal file
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@ -0,0 +1,16 @@
// Copyright 2017 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
function fun() {};
fun.prototype = 42;
new fun();
function f() {
return fun.prototype;
}
assertEquals(42, f());
assertEquals(42, f());
%OptimizeFunctionOnNextCall(f);
assertEquals(42, f());