The implementation makes use of the freedom added by LWG 3410. We have
two variants of this algorithm:
* a fast path for random access iterators: This fast path computes the
maximum number of loop iterations up-front and does not compare the
iterators against their limits on every loop iteration.
* A basic implementation for all other iterators: This implementation
compares the iterators against their limits in every loop iteration.
However, it still takes advantage of the freedom added by LWG 3410 to
avoid unnecessary additional iterator comparisons, as originally
specified by P1614R2.
https://godbolt.org/z/7xbMEen5e shows the benefit of the fast path:
The hot loop generated of `lexicographical_compare_three_way3` is
more tight than for `lexicographical_compare_three_way1`. The added
benchmark illustrates how this leads to a 30% - 50% performance
improvement on integer vectors.
Implements part of P1614R2 "The Mothership has Landed"
Fixes LWG 3410 and LWG 3350
Differential Revision: https://reviews.llvm.org/D131395
This has multiple benefits:
- The optimizations are also performed for the `ranges::` versions of the algorithms
- Code duplication is reduced
- it is simpler to add this optimization for other segmented iterators,
like `ranges::join_view::iterator`
- Algorithm code is removed from `<deque>`
Reviewed By: ldionne, huixie90, #libc
Spies: mstorsjo, sstefan1, EricWF, libcxx-commits, mgorny
Differential Revision: https://reviews.llvm.org/D132505
Bumping down is significantly faster than bumping up. This is ABI breaking, but the ABI of `pmr::monotonic_buffer_resource` was only stabilized in this release cycle, so we can still change it.
For a more detailed explanation why bumping down is better, see https://fitzgeraldnick.com/2019/11/01/always-bump-downwards.html.
Reviewed By: ldionne, #libc
Spies: libcxx-commits
Differential Revision: https://reviews.llvm.org/D141435
In particular remove the ability to expel incomplete features from the
library at configure-time, since this can now be done through the
_LIBCPP_ENABLE_EXPERIMENTAL macro.
Also, never provide symbols related to incomplete features inside the
dylib, instead provide them in c++experimental.a (this changes the
symbols list, but not for any configuration that should have shipped).
Differential Revision: https://reviews.llvm.org/D128928
This is a preparation to look at possible performance improvements.
Reviewed By: #libc, ldionne
Differential Revision: https://reviews.llvm.org/D129421
The optimization level used when building the benchmarks should
match the optimization level of the current build. Otherwise, we
can end up mixing an -O3 or -O0 optimized dylib with benchmarks
built with -O2, which is really misleading.
Differential Revision: https://reviews.llvm.org/D127987
Standalone builds have been deprecated and then removed for a while now.
Trying to use standalone builds leads to a fatal CMake error, so this
code is all dead. Remove it to clean things up.
Differential Revision: https://reviews.llvm.org/D125561
This reverts commit b2fbd45d2395f1f6ef39db72b7156724fc101e40. D114922
fixed the reason of the 2nd revert.
This patch also re-applies 39e9f5d3685f3cfca0df072928ad96d973704dff.
Differential Revision: https://reviews.llvm.org/D112012
This reverts commit e7568b68da8a216dc22cdc1c6d8903c94096c846 and relands
c6f7b720ecfa6db40c648eb05e319f8a817110e9.
The culprit was: missed that libc also had a dependency on one of the
copies of `google-benchmark`
Also opportunistically fixed indentation from prev. change.
Differential Revision: https://reviews.llvm.org/D112012
under third-party
This change:
- moves the libcxx copy of `google/benchmark` to
`third-party/benchmkark`
- points the 2 uses of the library (libcxx and llvm/utils) to this copy
We picked the licxx copy because it is the most up to date.
Differential Revision: https://reviews.llvm.org/D112012
We are trying to remove duplication of third-party code in
https://reviews.llvm.org/D112012, which will move the Google
Benchmark code outside of the `libcxx/` directory. That breaks
running the benchmarks in the Standalone build. Since we have
deprecated the Standalone build anyway, this patch just removes
support for the benchmark in Standalone mode until we remove that
mode entirely.
Differential Revision: https://reviews.llvm.org/D113503
The CMake dependencies don't properly list the libc++ headers. When a
libc++ header is modified the affected benchmarks aren't rebuild. This
makes testing benchmarks tricky and may cause accidentally not using the
latest modifications during testing. This change causes CMake to
determine the proper dependencies.
This shouldn't affect the CI build.
Reviewed By: #libc, ldionne
Differential Revision: https://reviews.llvm.org/D113419
This enforces libcxx and its benchmarks are compiled by a C++20 capable
compiler. Based on review comments in D103413.
Differential Revision: https://reviews.llvm.org/D110338
This is a re-application of da0592e4c8df which was reverted in
1454018dc1d9 because it was incompatible with older CMakes.
Instead, disable the benchmarks when CMake is too old to
support those idioms.
Differential Revision: https://reviews.llvm.org/D110285
When using the per-target runtime build, it may be desirable to have
different __config_site headers for each target where all targets cannot
share a single configuration.
The layout used for libc++ headers after this change is:
```
include/
c++/
v1/
<libc++ headers except for __config_site>
<target1>/
c++/
v1/
__config_site
<target2>/
c++/
v1/
__config_site
<other targets>
```
This is the most optimal layout since it avoids duplication, the only
headers that's per-target is __config_site, all other headers are
shared across targets. This also means that we no need two
-isystem flags: one for the target-agnostic headers and one for
the target specific headers.
Differential Revision: https://reviews.llvm.org/D89013
Prior to this patch, we would generate a fancy <__config> header by
concatenating <__config_site> and <__config>. This complexifies the
build system and also increases the difference between what's tested
and what's actually installed.
This patch removes that complexity and instead simply installs <__config_site>
alongside the libc++ headers. <__config_site> is then included by <__config>,
which is much simpler. Doing this also opens the door to having different
<__config_site> headers depending on the target, which was impossible before.
It does change the workflow for testing header-only changes to libc++.
Previously, we would run `lit` against the headers in libcxx/include.
After this patch, we run it against a fake installation root of the
headers (containing a proper <__config_site> header). This makes use
closer to testing what we actually install, which is good, however it
does mean that we have to update that root before testing header changes.
Thus, we now need to run `ninja check-cxx-deps` before running `lit` by
hand.
Differential Revision: https://reviews.llvm.org/D97572
Some work-in-progress patches for the format header contain benchmarks.
The format header requires C++20 to build. This is a preparation to make
it easy to add these benchmarks.
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D96057
This is a massive revert of the following commits (from most revent to oldest):
2b9b7b5775a1d8fcd7aa5abaa8fc0bc303434f1a.
529ac33197f6408952ae995075ac5e2dc5287e81
28270234f1478047e35879f4ba8838b47edfcc14
69c2087283cf7b17ca75f69daebf4ffc158b754a
b5aa67446e01bd277727b05710a42e69ac41e74b
5d796645d6c8cadeb003715c33e231a8ba05b6de
After checking-in the __config_site change, a lot of things started breaking
due to widespread reliance on various aspects of libc++'s build, notably the
fact that we can include the headers from the source tree, but also reliance
on various "internal" CMake variables used by the runtimes build and compiler-rt.
These were unintended consequences of the change, and after two days, we
still haven't restored all the bots to being green. Instead, now that I
understand what specific areas this will blow up in, I should be able to
chop up the patch into smaller ones that are easier to digest.
See https://reviews.llvm.org/D89041 for more details on this adventure.
The benchmarks expect to be built in C++17 or newer, but this
isn't always how CMake configures the C++ dialect. Instead
we need to explicitly set the CXX_STANDARD target property.
Before this patch, the __config_site header was only generated when at
least one __config_site macro needed to be defined. This lead to two
different code paths in how libc++ is configured, depending on whether
a __config_site header was generated or not. After this patch, the
__config_site is always generated, but it can be empty in case there
are no macros to define in it.
More context on why this change is important
--------------------------------------------
In addition to being confusing, this double-code-path situation lead to
broken code being checked in undetected in 2405bd689815, which introduced
the LIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT CMake setting. Specifically,
the _LIBCPP_HAS_MERGED_TYPEINFO_NAMES_DEFAULT <__config_site> macro was
supposed NOT to be defined unless LIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT
was specified explicitly on the CMake command line. Instead, what happened
is that it was defined to 0 if it wasn't specified explicitly and a
<__config_site> header was generated. And defining that macro to 0 had
the important effect of using the non-unique RTTI comparison implementation,
which changes the ABI.
This change in behavior wasn't noticed because the <__config_site> header
is not generated by default. However, the Apple configuration does cause
a <__config_site> header to be generated, which lead to the wrong RTTI
implementation being used, and to https://llvm.org/PR45549. We came close
to an ABI break in the dylib, but were saved due to a downstream-only
change that overrode the decision of the <__config_site> for the purpose
of RTTI comparisons in libc++abi. This is an incredible luck that we should
not rely on ever again.
While the problem itself was fixed with 2464d8135e2a by setting
LIBCXX_HAS_MERGED_TYPEINFO_NAMES_DEFAULT explicitly in the Apple
CMake cache and then in d0fcdcd28f95 by making the setting less
brittle, the point still is that we should have had a single code
path from the beginning. Unlike most normal libraries, the macros
that configure libc++ are really complex, there's a lot of them and
they control important properties of the C++ runtime. There must be
a single code path for that, and it must be simple and robust.
Differential Revision: https://reviews.llvm.org/D80927
The benchmarks are intended to be build with C++17 but the
CMAKE_CXX_STANDARD in the LLVM forces the build to use C++14 by default.
This fixes the issue by setting the CXX_STANDARD property of the benchmark
targets.
The CMake documentation is not clear whether this will use the C++1z
fallback for older compilers. So this may break the benchmarks if somebody
uses the benchmarks with pre C++17 compilers with the C++1z fallback.
Differential Revision: https://reviews.llvm.org/D75955
It turns out that r374056 broke _some_ build bots again, specifically
the ones using sanitizers. Instead of trying to link the right system
libraries to the benchmarks bit-by-bit, let's just link exactly the
system libraries that libc++ itself needs.
llvm-svn: 374079
Since the benchmarks build with -nostdlib, they need to manually link
against some system libraries that are used by the benchmarks and the
GoogleBenchmark library itself.
Previously, we'd rely on the fact that these libraries were linked
through the PUBLIC dependencies of cxx_shared/cxx_static. However,
if we were to make these dependencies PRIVATE (as they should be
because they are implementation details of libc++), the benchmarks
would fail to link. This commit remediates that.
llvm-svn: 374053
It's better style to use PRIVATE when linking libraries to executables,
and it doesn't make a difference since executables don't need to propagate
their link-time dependencies anyway.
llvm-svn: 374050
This allows propagating the include automatically to targets that
depend on one of the libc++ targets such as the benchmarks. Note
that the GoogleBenchmark build itself still needs to manually specify
the -include, since I don't know of any way to have an external project
link against one of the libc++ targets (which would propagate the -include
automatically).
llvm-svn: 373631
Summary:
Instead of populating the global LIBCXX_LIBRARIES, we use the link-time
dependency management built into CMake to propagate link flags. This
leads to a cleaner and easier-to-follow build.
Reviewers: phosek, smeenai, EricWF
Subscribers: mgorny, christof, jkorous, dexonsmith, jfb, mstorsjo, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D60969
llvm-svn: 359571
Summary:
This patch treats <filesystem> as a first-class citizen of the dylib,
like all other sub-libraries (e.g. <chrono>). As such, it also removes
all special handling for installing the filesystem library separately
or disabling part of the test suite from the lit command line.
Unlike the previous attempt (r356500), this doesn't remove all the
filesystem tests.
Reviewers: mclow.lists, EricWF, serge-sans-paille
Subscribers: mgorny, christof, jkorous, dexonsmith, jfb, jdoerfert, libcxx-commits
Differential Revision: https://reviews.llvm.org/D59152
llvm-svn: 356518
When I applied r356500 (https://reviews.llvm.org/D59152), I somehow
deleted all of filesystem's tests. I will revert r356500 and re-apply
it properly.
llvm-svn: 356505
Summary:
This patch treats <filesystem> as a first-class citizen of the dylib,
like all other sub-libraries (e.g. <chrono>). As such, it also removes
all special handling for installing the filesystem library separately
or disabling part of the test suite from the lit command line.
Reviewers: mclow.lists, EricWF, serge-sans-paille
Subscribers: mgorny, christof, jkorous, dexonsmith, jfb, jdoerfert, libcxx-commits
Differential Revision: https://reviews.llvm.org/D59152
llvm-svn: 356500
When linking library dependencies, we shouldn't need to export linked
libraries to dependents. We should be explicit about this in
target_link_libraries, otherwise other targets that depend on these such
as sanitizers get repeated (and possibly even conflicting) dependencies.
Differential Revision: https://reviews.llvm.org/D57456
llvm-svn: 352688
