This introduces a new {base::SharedMutex}, which mimics
{std::shared_mutex}, available in C++17.
It is being used for synchronizing the WebAssembly background compile
tasks. This removes a lot of unnecessary contention, leading to
synchronization of background tasks that should be able to run in
parallel ideally.
Locally, this reduces Liftoff compilation time by more than 20 percent.

R=mstarzinger@chromium.org, mlippautz@chromium.org

Bug: chromium:924956
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel
Change-Id: I8c522faf385149bfe2cf00d777a7942c537f9cd2
Reviewed-on: https://chromium-review.googlesource.com/c/1477731
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59729}

New code should use nullptr instead of NULL.

This patch updates existing use of NULL to nullptr where applicable,
making the code base more consistent.

BUG=v8:6928,v8:6921

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng;master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I4687f5b96fcfd88b41fa970a2b937b4f6538777c
Reviewed-on: https://chromium-review.googlesource.com/718338
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48557}

SRWLOCK is a faster and lightweight alternative of CRITICAL_SECTION for
non-recursive use case.

Bug: chromium:592752
Change-Id: Ie97cd9cee2d50a95f316b41c30e953f586b06c99
Reviewed-on: https://chromium-review.googlesource.com/520828Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Loo Rong Jie <loorongjie@gmail.com>
Cr-Commit-Position: refs/heads/master@{#45658}

Default to the chromium-internal build config (instead of the more
permissive no_chromium_code config).

BUG=v8:5878

Review-Url: https://codereview.chromium.org/2758563002
Cr-Commit-Position: refs/heads/master@{#43909}

This enables linter checking for "readability/namespace" violations
during presubmit and instead marks the few known exceptions that we
allow explicitly.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1371083003

Cr-Commit-Position: refs/heads/master@{#31019}

This way we don't clash with the ASSERT* macros
defined by GoogleTest, and we are one step closer
to being able to replace our homegrown base/ with
base/ from Chrome.

R=jochen@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/430503007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22812 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

Also split v8-core independent methods from checks.h to base/logging.h and
merge v8checks with the rest of checks.

The CPU::FlushICache method is moved to CpuFeatures::FlushICache

RoundUp and related methods are moved to base/macros.h

Remove all layering violations from src/libplatform

BUG=none
R=jkummerow@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/358363002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22092 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

- this avoids using relative include paths which are forbidden by the style guide
- makes the code more readable since it's clear which header is meant
- allows for starting to use checkdeps

BUG=none
R=jkummerow@chromium.org, danno@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/304153016

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21625 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/259183002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@21035 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

Some libraries (e.g. Dinkumware) perform strict checks on whether
the symbols defined in classic C library headers (e.g. <stdio.h>),
or in C++-style C library headers (e.g. <cmath>) are used correctly
(respectively, in the global namespace, or in namespace std).

BUG=
R=danno@chromium.org

Review URL: https://codereview.chromium.org/121303005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18578 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/23604054

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16669 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

Original descriptions were:
- "Refactor and cleanup VirtualMemory."
- "Fix typo."
- "Deuglify V8_INLINE and V8_NOINLINE."
- "Don't align size on allocation granularity for unaligned ReserveRegion calls."

Reasons for the revert are:
- Our mjsunit test suite slower by a factor of 5(!) in release mode.
- Flaky cctest/test-alloc/CodeRange on all architectures and platforms.
- Tankage of Sunspider by about 6% overall (unverified).

TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23970004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16662 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/23494047

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16641 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

Condition variables are synchronization primitives that can be used
to block one or more threads while waiting for condition to become
true.

Right now we have only semaphores, mutexes and atomic operations for
synchronization, which results in quite complex solutions where an
implementation using condition variables and mutexes would be straight
forward.

There's also a performance benefit to condition variables and mutexes
vs semaphores, especially on Windows, where semaphores are kernel
objects, while mutexes are implemented as fast critical sections,
it CAN be beneficial performance-wise to use condition variables
instead of semaphores.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/23548007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16492 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

Drop the previous Mutex and ScopedLock classes from platform files.

Add new Mutex, RecursiveMutex and LockGuard classes, which are
designed after their C++11 counterparts, so that at some point
we can simply drop our custom code and switch to the C++11
classes. We distinguish regular and recursive mutexes, as the
latter don't work well with condition variables, which will be
introduced by a followup CL.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/23625003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16416 ce2b1a6d-e550-0410-aec6-3dcde31c8c00