commit | f597eec152eb5c5b788c73eaa689553000f5fa36 | [log] [tgz] |
---|---|---|
author | Benedikt Meurer <bmeurer@chromium.org> | Wed Nov 01 20:41:22 2017 |
committer | Commit Bot <commit-bot@chromium.org> | Thu Nov 02 06:39:34 2017 |
tree | dd129475acf7f77f27717abd5e1997ec42a3c8f3 | |
parent | c9168fc5deaead5235468e55d117df0fa2fb69b4 [diff] |
[builtins] Support two byte strings in StringEqual builtin. This CL adds support for two byte string comparisons to the StringEqual builtin, which so far was bailing out to the generic %StringEqual runtime function whenever any two-byte string was involved. This made comparisons that involved two-byte strings, either comparing them to one-byte strings or comparing two two-byte strings, up to 3x slower than if only one-byte strings were involved. With this change, all direct string (SeqString or ExternalString) equality checks are roughly on par now, and the weird performance cliff is gone. On the micro-benchmark from the bug we go from stringEqualBothOneByteSeqString: 162 ms. stringEqualTwoByteAndOneByteSeqString: 446 ms. stringEqualOneByteAndTwoByteSeqString: 438 ms. stringEqualBothTwoByteSeqString: 472 ms. to stringEqualBothOneByteSeqString: 151 ms. stringEqualTwoByteAndOneByteSeqString: 158 ms. stringEqualOneByteAndTwoByteSeqString: 166 ms. stringEqualBothTwoByteSeqString: 160 ms. which is the desired result. On the esprima test of the web-tooling-benchmark we seem to improve by 1-2%, which corresponds to the savings of going to the runtime for many StringEqual comparisons. Drive-by-cleanup: Introduce LoadAndUntagStringLength helper into the CSA with proper typing to avoid the unnecessary shifts on 64-bit platforms when keeping the length tagged initially in StringEqual. Bug: v8:4913, v8:6365, v8:6371, v8:6936, v8:7022 Change-Id: I566f4b80e217513775ffbd35e0480154abf59b27 Reviewed-on: https://chromium-review.googlesource.com/749223 Reviewed-by: Yang Guo <yangguo@chromium.org> Commit-Queue: Benedikt Meurer <bmeurer@chromium.org> Cr-Commit-Position: refs/heads/master@{#49067}
V8 is Google's open source JavaScript engine.
V8 implements ECMAScript as specified in ECMA-262.
V8 is written in C++ and is used in Google Chrome, the open source browser from Google.
V8 can run standalone, or can be embedded into any C++ application.
V8 Project page: https://github.com/v8/v8/wiki
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