6452b26a4b
Previously, V8's slice was implemented in a combination of C++ and a Javascript fallback. The disadvantage of this approach was that the fast-path required a call through the CEntryStub, which introduced considerable overhead for small arrays with fast elements kinds. Now the implementation primarily uses the CSA to generate both the full spec-complaint implementation as well as fast paths for argument objects and arrays with fast elements kinds. The CSA implementation uses a C++ implementation fallback in select situations where the the complexity of a CSA implementation would be too great and the CEntryStub overhead is not decisive (e.g. slices of dictionary elements arrays). Performance results on semi-random arrays with small number of elements (old vs. new): smi copy: 48.7 ms vs. 12 ms smi slice: 43.5 ms 14.8 ms object copy: 35.5 ms 7.7 ms object slice: 38.7 ms 8.8 ms dictionary slice: 2398.3 ms vs. 5.4 ms fast sloppy arguments slice: 9.6 ms vs. 7.2 ms slow sloppy arguments slice: 28.9 ms vs. 8.5 ms As a bonus, the new implementation is fully spec-compliant and fixes at least one existing bug. The design document for Array.prototype builtin rework can be found at https://goo.gl/wFHe2n Bug: v8:1956,v8:6601,v8:6710,v8:6978 Change-Id: Ia0155bedcf39b4577605ff754f416c2af938efb7 Reviewed-on: https://chromium-review.googlesource.com/574710 Commit-Queue: Daniel Clifford <danno@chromium.org> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org> Cr-Commit-Position: refs/heads/master@{#48853}
14 lines
385 B
JavaScript
14 lines
385 B
JavaScript
// Copyright 2017 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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var array = [];
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var proxy = new Proxy(new Proxy(array, {}), {});
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var Ctor = function() {};
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var result;
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array.constructor = function() {};
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array.constructor[Symbol.species] = Ctor;
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Array.prototype.slice.call(proxy);
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