08db4d7652
Until now keyed accesses to properties with string or symbol keys were only optimized properly while the IC was monomorphic and would go megamorphic as soon as there's another receiver map, even if the name was still the same (i.e. the same symbol or internalized string). This was a weird performance-cliff, that'll hurt modern code especially because for symbols you can only access them via keyed loads and stores. This CL fixes the state machine inside the ICs to properly transition to POLYMORPHIC state (and stay there) as long as the new name matches the previously recorded name. The FeedbackVector and TurboFan were already able to deal with this and didn't need any updates. On the micro-benchmark from the tracking bug we go from testStringMonomorphic: 429 ms. testSymbolMonomorphic: 431 ms. testStringPolymorphic: 429 ms. testSymbolPolymorphic: 5621 ms. to testStringMonomorphic: 429 ms. testSymbolMonomorphic: 429 ms. testStringPolymorphic: 429 ms. testSymbolPolymorphic: 430 ms. effectively eliminating the overhead for symbols completely, and yielding a 13.5x performance boost. This also seems to yield a 1% improvement on the ARES6 ML benchmark, because it eliminates the KEYED_LOAD_ICs for the Symbol.species lookups. Bug: v8:6367, v8:6278, v8:6344 Change-Id: I879fe56387b4c56203c1ad8ef8cafb6cc4c32897 Reviewed-on: https://chromium-review.googlesource.com/695108 Reviewed-by: Michael Stanton <mvstanton@chromium.org> Commit-Queue: Benedikt Meurer <bmeurer@chromium.org> Cr-Commit-Position: refs/heads/master@{#48261}
49 lines
1.1 KiB
JavaScript
49 lines
1.1 KiB
JavaScript
// Copyright 2015 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Flags: --allow-natives-syntax
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(function() {
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const symbol = Symbol('symbol');
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const OBJS = [
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{[symbol]: 0, a: 1},
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{[symbol]: 1, b: 2},
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{[symbol]: 2, c: 3},
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{[symbol]: 3, d: 4}
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];
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function foo(o) { return o[symbol]; }
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for (let i = 0; i < OBJS.length; ++i) {
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assertEquals(i, foo(OBJS[i]));
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assertEquals(i, foo(OBJS[i]));
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}
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%OptimizeFunctionOnNextCall(foo);
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for (let i = 0; i < OBJS.length; ++i) {
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assertEquals(i, foo(OBJS[i]));
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assertEquals(i, foo(OBJS[i]));
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}
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})();
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(function() {
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const symbol = Symbol('symbol');
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const OBJS = [
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{[symbol]: 0, a: 1},
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{[symbol]: 1, b: 2},
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{[symbol]: 2, c: 3},
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{[symbol]: 3, d: 4}
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];
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function foo(o) { o[symbol] = o; }
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for (let i = 0; i < OBJS.length; ++i) {
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foo(OBJS[i]);
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foo(OBJS[i]);
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}
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%OptimizeFunctionOnNextCall(foo);
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for (let i = 0; i < OBJS.length; ++i) {
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foo(OBJS[i]);
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foo(OBJS[i]);
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}
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for (const o of OBJS) {
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assertEquals(o, o[symbol]);
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}
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})();
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