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Jaroslav Sevcik 6a08d18de2 [turbofan] Better type and truncation for speculative additive ops. 
This helps with patterns such as

((a[i] + n) + m) | 0

where we know n and m are small integers, and a[i] is a holey smi
array where we have never read a hole so far.

In that case, we still perform the additions with overflow checks
since we currently only propagate/use the truncation if the operation
outcome is in the safe-integer range (without taking feedback into
account).  The problem here is that both 'n + a[i]' and '(n + a[i]) +
m' have type Union(Range(..., ...), NaN), even though the NaN will
never pass the Smi check on a[i].

This CL changes restricts the static type of 
SpeculativeSafeInteger(Add|Subtract) to the safe integer range. 
This is safe because we will always either truncate or use the feedback
(i.e., deopt if the inputs are not Signed32).  In either case, the 
result will always be in safe-integer range.

As a result, we will perform the second addition without
overflow check. Getting rid of the overflow check on the first
is done in a separate CL.

Bug: v8:5267,v8:6764
Change-Id: I27dba0fda832fc1f04477db6dd3495d5b4b2bd0b
Reviewed-on: https://chromium-review.googlesource.com/634903
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47763}
2017-09-01 10:27:22 +00:00
benchmarks Fix common misspellings 2017-08-02 09:35:28 +00:00
build_overrides Remove build_override for macOS min SDK and deployment target. 2017-07-14 18:24:44 +00:00
docs [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
gni add gn jumbo build support 2017-08-09 09:05:29 +00:00
gypfiles [gyp] Disable compiler warning 2017-08-29 11:52:47 +00:00
include Updated version to 6.3 2017-08-31 11:21:35 +00:00
infra [build] Add MB config for win64 asan bots 2017-08-16 14:01:31 +00:00
samples Pass Isolate pointer to String::Utf8Value/Value constructors 2017-08-28 18:17:08 +00:00
src [turbofan] Better type and truncation for speculative additive ops. 2017-09-01 10:27:22 +00:00
test [turbofan] Support inline allocation of mapped outer arguments. 2017-09-01 09:52:59 +00:00
testing Use GTEST_LANG_CXX11 in V8 2016-07-25 13:06:42 +00:00
third_party Remove myself from non-toplevel owners files 2017-06-28 10:00:48 +00:00
tools [promise] Reduce size of PromiseCapability by making it a struct 2017-08-31 04:20:16 +00:00
.clang-format [clang-format] Don't derive pointer alignment 2017-01-17 09:28:19 +00:00
.editorconfig Add .editorconfig 2017-07-28 13:39:24 +00:00
.gitignore add .vscode to .gitignore 2017-08-14 23:18:09 +00:00
.gn For building v8 using gn on aix_ppc64, linux_s390x and linux_ppc64(both LE and BE). 2017-05-12 01:35:09 +00:00
.ycm_extra_conf.py Use C++11 / gnu++11, not 0x 2016-03-22 15:24:43 +00:00
AUTHORS Pass Isolate pointer to String::Utf8Value/Value constructors 2017-08-28 18:17:08 +00:00
BUILD.gn [builtins] Port Proxy set trap to CSA 2017-09-01 09:23:47 +00:00
ChangeLog [Release] Update ChangeLog file 2016-02-17 21:29:09 +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
DEPS Update V8 DEPS. 2017-08-29 03:54:28 +00:00
LICENSE Updates to the license information of third party components. 2015-06-16 12:37:50 +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
Makefile [heap] Port concurrent marking flag to GYP. 2017-08-23 15:26:43 +00:00
Makefile.android [build] Fix d8-for-Android builds 2016-05-20 12:10:45 +00:00
OWNERS Add eholk and gdeepti to toplevel owners 2017-08-12 07:07:29 +00:00
PRESUBMIT.py [test] Automatically add a noi18n bot for changes affecting Intl 2017-06-06 13:01:14 +00:00
README.md [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
snapshot_toolchain.gni MIPS[64]: Add support for big endian build using GN 2017-06-02 15:02:18 +00:00
WATCHLISTS [V8Tracing] Add lpy@ and fmeawad@ into watchlist for tracing/. 2017-05-22 19:40:17 +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://github.com/v8/v8/wiki

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 on the V8 wiki.