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jarin f0e41175fd [turbofan] Bidirectional representation inference. 
This changes representation inference to be bidirectional:
1. truncations are propagated from uses to definitions.
2. output types are propagated from definitions to uses.
(and nodes are revisited until fixpoint.)

At the moment, (2) is used only superficially; the idea here is to
use the output type propagation to propagate types from type feedback.

For the output types to be usable, we need to keep track of the type
of the JavaScript value rather than the truncated value. Otherwise,
representation inference could not rely on the ranges indicated
by the values.

For example, for "var b = (a|0) + (a|0); return (b/16) >>> 0",
the type of b cannot be int32; otherwise the division "b/16"
would believe that it is fine to do an integer division on
the truncated value, which would give a wrong result for
2^31 <= a < 2^32.

The change makes representation inference a bit more expensive
(the phase is about 20% slower), but since this is only small part
of the overall compiler time, the overall effect is negligible.
If the running time becomes a problem, we could optimize this by
remembering when the nodes are stable (ie., no further changes to
type/truncations) and/or explicit subscriptions for changes.

BUG=v8:4583
R=bmeurer@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1490763003

Cr-Commit-Position: refs/heads/master@{#33112}
2016-01-05 11:56:39 +00:00
benchmarks Revert "Refactoring: Make gtest testsuite the default." 2014-09-02 09:17:26 +00:00
build [test] Add ignition test set. 2016-01-04 17:26:42 +00:00
docs [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
include [proxies] Expose proxies in the API 2015-12-22 16:37:24 +00:00
infra Revert of [CQ] Temporarily switch off pure swarming bots. (patchset #1 id:1 of https://codereview.chromium.org/1502143005/ ) 2015-12-09 07:43:41 +00:00
samples Disable soon to be deprecated APIs per default for v8 2015-12-09 10:35:04 +00:00
src [turbofan] Bidirectional representation inference. 2016-01-05 11:56:39 +00:00
test [Interpreter] Adds support for wide variant of load/store lookup slots. 2016-01-05 11:36:48 +00:00
testing Converted V8 CQ config to proto-format 2015-05-28 15:02:53 +00:00
third_party/binutils Update binutils version. 2015-08-07 08:09:49 +00:00
tools Add a --harmony-species flag, defining @@species on constructors 2016-01-04 19:39:59 +00:00
.clang-format Change clang-format config to allow for two empty lines between functions 2013-12-03 10:39:21 +00:00
.gitignore Update DEPS entry for tracing to point at correct location 2015-12-16 12:17:06 +00:00
.ycm_extra_conf.py [ycm] The YouCompleteMe configuration is not VIM specific. 2015-02-12 07:21:13 +00:00
AUTHORS Add Isolate::DiscardThreadSpecificMetadata method to embedder API. 2015-12-16 15:49:49 +00:00
BUILD.gn Add a --harmony-species flag, defining @@species on constructors 2016-01-04 19:39:59 +00:00
ChangeLog Update change log to match roll branch. 2015-05-18 15:03:50 +00:00
codereview.settings Use v8-reviews@ for review mail, so v8-dev@ is free for dev discussions 2015-09-09 08:14:11 +00:00
DEPS Update V8 DEPS. 2015-12-31 08:34:30 +00:00
LICENSE Updates to the license information of third party components. 2015-06-16 12:37:50 +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 Revert of Remove wasm compile time option and enable wasm behind a runtime flag. (patchset #54 id:1050001 of https://codereview.chromium.org/1516753007/ ) 2015-12-17 17:59:00 +00:00
Makefile.android Reland [android] Migrate more configs to gyp. 2015-06-26 12:04:09 +00:00
Makefile.nacl Use the pnacl-clang toolchain for (P)NaCL builds 2014-10-06 08:10:50 +00:00
OWNERS Update OWNERS file. 2015-07-16 11:37:51 +00:00
PRESUBMIT.py [CQ] Add new triggered win trybots to CQ. 2015-12-03 15:01:06 +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 Map arm64 and mips64el -> x64 for mksnapshot 2015-12-16 15:17:37 +00:00
WATCHLISTS [Release] CC hpayer@ and ulan@ to every heap change 2015-12-02 12:49:50 +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.