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Jakob Gruber fb5c7c879e Revert "[regalloc] Use an adaptive data structure for live sets" 
This reverts commit b3d748a282.

Reason for revert: Regressions, see https://crbug.com/1023423.

Original change's description:
> [regalloc] Use an adaptive data structure for live sets
> 
> Live sets represent sets of live virtual registers at block entry and
> exit points. They are usually sparsely populated; for example, a sample
> taken from Octane2 shows 80% of sampled live sets with a fill ratio of
> 10% or less.
> 
> Prior to this CL, live sets were implemented as a statically-sized bit
> vector. This is fine for low-ish virtual register counts, but becomes
> wasteful at higher numbers.
> 
> This CL attempts to address this issue through an adaptive
> implementation. Small live sets remain bit vectors, while larger sets
> switch to a PersistentMap-based implementation. PersistentMap has very
> memory-efficient add/remove/copy operations.
> 
> Of course, with adaptive data structures we enter the territory of
> parameter fiddling. In this case, two parameters are used:
> kMaxSmallSetSize controls when to switch implementations, and
> kMaxDeletionsBeforePrune controls when pruning (= managing the # of
> deleted entries in the map) sets in.
> 
> On the (degenerate) test case from the linked bug, the register
> allocation zone shrinks from 1008MB to 475MB. For more realistic cases
> I expect savings on the order of 10s of KB.
> 
> Bug: v8:9574
> Change-Id: Id903bbe23f030b418e8d887ef4839c8d65126c52
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1891693
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#64872}

TBR=jgruber@chromium.org,tebbi@chromium.org,thibaudm@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: v8:9574
Change-Id: I5d684198f9c4575a0c892076459cc2c20dce9aec
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1910944
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64912}
2019-11-12 12:24:02 +00:00
build_overrides Use relative paths to OWNERS files 2019-08-12 13:52:52 +00:00
custom_deps Use relative paths to OWNERS files 2019-08-12 13:52:52 +00:00
docs Add OWNERS for docs/ 2019-05-15 12:06:15 +00:00
gni [build] Move split_static_library.gni from Chromium repo 2019-11-04 15:45:54 +00:00
include [builtins] Allow 2Gb TypedArrays on 64-bit architectures 2019-11-11 21:42:56 +00:00
infra [build] Remove unused trace-pc-guard coverage from clusterfuzz builds 2019-11-12 10:41:22 +00:00
samples [cleanup] Drop some occurrences of Isolate::Current 2019-06-26 19:39:21 +00:00
src Revert "[regalloc] Use an adaptive data structure for live sets" 2019-11-12 12:24:02 +00:00
test [turbofan][64] Remove Smi Untagging extra nodes for 31 bit smis 2019-11-12 12:06:11 +00:00
testing Use relative paths to OWNERS files 2019-08-12 13:52:52 +00:00
third_party [DevTools] Roll inspector_protocol (v8) (file split) 2019-11-12 10:27:01 +00:00
tools [foozzie] Remove per-testcase random seed 2019-11-12 12:21:51 +00:00
.clang-format [clang-format] Don't derive pointer alignment 2017-01-17 09:28:19 +00:00
.clang-tidy [tool] Remove unfixed clang-tidy warnings to ease use. 2018-10-26 07:40:32 +00:00
.editorconfig Add .editorconfig 2017-07-28 13:39:24 +00:00
.flake8 Add .flake8 to allow for python style checking. 2019-07-19 21:44:03 +00:00
.git-blame-ignore-revs Add recent code rewrite to .git-blame-ignore-revs 2019-05-23 10:38:45 +00:00
.gitattributes .gitattributes: Mark minified emscripten js files as -diff 2018-09-19 16:27:10 +00:00
.gitignore Remove MIPS(64) builders from V8 infra 2019-09-16 11:20:11 +00:00
.gn [build] Dynamically decide if to use system xcode 2019-07-29 08:20:24 +00:00
.vpython [tools] Implement confidence-based number of runs 2019-05-09 09:42:28 +00:00
.ycm_extra_conf.py [ycm] Switch from gnu++11 to gnu++14 2017-11-27 07:48:21 +00:00
AUTHORS [builtins] Port Number.prototype.toString to Torque 2019-11-05 11:00:26 +00:00
BUILD.gn [build] Simplify snapshot target 2019-11-12 11:55:06 +00:00
ChangeLog [release] Merge ChangeLog back to master 2018-12-07 15:41:59 +00:00
CODE_OF_CONDUCT.md
codereview.settings Make Gerrit the default code review for V8 2017-06-30 17:37:37 +00:00
COMMON_OWNERS Rename clemensh to clemensb in OWNERS 2019-09-26 08:44:44 +00:00
DEPS Update V8 DEPS. 2019-11-12 03:49:11 +00:00
ENG_REVIEW_OWNERS Add eng review owners as escalation path 2019-05-15 19:12:10 +00:00
INFRA_OWNERS Clean up infra owners 2019-05-15 11:18:43 +00:00
INTL_OWNERS Add missing owners files 2019-05-31 07:21:01 +00:00
LICENSE [wasm] Draft version of C/C++ Wasm API 2019-04-17 16:00:26 +00:00
LICENSE.fdlibm Add LICENSE.fdlibm for all the fdlibm imported sources. 2016-06-09 07:17:03 +00:00
LICENSE.strongtalk
LICENSE.v8
LICENSE.valgrind
MIPS_OWNERS Move architecture dependent files 2019-05-28 14:02:15 +00:00
OWNERS Add syg@chromium.org as DEPS owner for test262 rolls 2019-09-17 19:29:11 +00:00
PPC_OWNERS Move architecture dependent files 2019-05-28 14:02:15 +00:00
PRESUBMIT.py Re-check all files on a DEPS change 2019-09-30 09:23:36 +00:00
README.md [docs] Change links from old wiki to v8.dev 2019-03-07 12:13:30 +00:00
S390_OWNERS Move architecture dependent files 2019-05-28 14:02:15 +00:00
WATCHLISTS Remove 'profiler' category from WATCHLISTS 2019-10-21 08:23:59 +00:00

README.md

V8 JavaScript Engine

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://v8.dev/docs

Getting the Code

Checkout depot tools, and run

    fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

    git pull origin
    gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*

Contributing

Please follow the instructions mentioned at v8.dev/docs/contribute.