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Mu Tao 76bc9a86e1 [mips][Liftoff] Improve initialization for many locals 
Port a8cdda9947

Original Commit Message:

    WebAssembly locals are specified to be zero on function entry. Liftoff
    implements this by just storing the constant 0 in the virtual stack for
    integer types, and using one floating point register initialized to
    zero for all floating point types.
    For big counts of locals this leads to problems (manifesting as huge
    blocks of code being generated) once we hit a merge point: All those
    constants (for int) and all duplicate register uses (for floats) need to
    be fixed up, by using separate registers for the locals or spilling to
    the stack if no more registers are available. All this spilling
    generates a lot of code, and can even happen multiple times within a
    function.

    This CL optimizes for such cases by spilling all locals to the stack
    initially. All merges within the function body get much smaller then.
    The spilled values rarely have to be loaded anyway, because the initial
    zero value is usually overwritten before the first use.

    To optimize the code size for initializing big numbers of locals on the
    stack, this CL also introduces the platform-specific
    {FillStackSlotsWithZero} method which uses a loop for bigger local
    counts.

    This often saves dozens of kilobytes for very big functions, and shows
    an overall code size reduction of 4-5 percent for big modules.

R=xwafish@gmail.com

Change-Id: Id65b6d36beadcba0d3f3726bb6559bb316cb212e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1862830
Auto-Submit: Mu Tao <pamilty@gmail.com>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Mu Tao <pamilty@gmail.com>
Cr-Commit-Position: refs/heads/master@{#64315}
2019-10-16 13:03:25 +00:00
benchmarks Use relative paths to OWNERS files 2019-08-12 13:52:52 +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 Reland "Unconditionally enable snapshot builds and remove 'v8_use_snapshot'" 2019-10-16 06:01:05 +00:00
include Reland "[runtime] Move Context::native_context to the map" 2019-10-16 12:32:03 +00:00
infra Reland "Unconditionally enable snapshot builds and remove 'v8_use_snapshot'" 2019-10-16 06:01:05 +00:00
samples [cleanup] Drop some occurrences of Isolate::Current 2019-06-26 19:39:21 +00:00
src [mips][Liftoff] Improve initialization for many locals 2019-10-16 13:03:25 +00:00
test Reland "[runtime] Move Context::native_context to the map" 2019-10-16 12:32:03 +00:00
testing Use relative paths to OWNERS files 2019-08-12 13:52:52 +00:00
third_party [DevTools] Roll inspector protocol (v8) 2019-10-11 21:22:31 +00:00
tools Reland "[runtime] Move Context::native_context to the map" 2019-10-16 12:32:03 +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 [log] report code relocation through CodeEventHandler 2019-09-24 10:50:05 +00:00
BUILD.gn Reland "Unconditionally enable snapshot builds and remove 'v8_use_snapshot'" 2019-10-16 06:01:05 +00:00
ChangeLog [release] Merge ChangeLog back to master 2018-12-07 15:41:59 +00:00
CODE_OF_CONDUCT.md Explicitly state that the Chromium Code of Conduct also applies to V8 2016-03-02 09:51:24 +00:00
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. 2019-10-16 03:33:44 +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 Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.v8 Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.valgrind Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
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 Move remaining files in src/ 2019-05-24 18:24:36 +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.