Commit Graph

108 Commits

Author SHA1 Message Date
Petr Hosek 96d8c6b571 [CMake] Remove {LIBCXX,LIBCXXABI,LIBUNWIND}_INSTALL_PREFIX
These variables were introduced during early work on the runtimes build
but were obsoleted by {LIBCXX,LIBCXXABI,LIBUNWIND}_INSTALL_LIBRARY_DIR.

Differential Revision: https://reviews.llvm.org/D99697
2021-04-01 10:13:07 -07:00
Petr Hosek 1687f2bbe2 [libcxxabi] Use cxx-headers target to consume libcxx headers
Rather than including libc++ include dir, use the cxx-headers target.

Differential Revision: https://reviews.llvm.org/D98367
2021-03-26 13:27:51 -07:00
Petr Hosek 74ed5124ba Revert "[libcxxabi] Use cxx-headers target to consume libcxx headers"
This reverts commit 72728e1280
which broke libcxxabi tests under the runtimes build.
2021-03-25 01:50:11 -07:00
jasonliu 158026301b [libc++][AIX] Initial patch to unblock the libc++ build on AIX
This path would unblock the build of libc++ library on AIX:
1. Add _AIX guard for _LIBCPP_HAS_THREAD_API_PTHREAD
2. Use uselocale to actually take the locale setting
   into account.
3. extract_mtime and extract_atime mod needed for AIX. As stat
   structure on AIX uses internal structure st_timespec to store
   time for binary compatibility reason. So we need to convert it
   back to timespec here.
4. Do not build cxa_thread_atexit.cpp for libcxxabi on AIX.

Differential Revision: https://reviews.llvm.org/D97558
2021-03-24 22:13:20 +00:00
Petr Hosek 72728e1280 [libcxxabi] Use cxx-headers target to consume libcxx headers
Rather than including libc++ include dir, use the cxx-headers target.

Differential Revision: https://reviews.llvm.org/D98367
2021-03-23 12:25:30 -07:00
Markus Böck 6359049c35 [CMake][runtimes] Add file level dependency to merge_archives commands
Both libc++ and libc++abi have options of merging with another archive. In the case of libc++abi, libunwind can be merged into it and in the case of libc++, libc++abi can be merged into it.

This is realized using add_custom_command with POST_BUILD and the usage of the CMake generator expression TARGET_LINKER_FILE in the arguments. For such generator expressions CMake doc states: "This target-level dependency does NOT add a file-level dependency that would cause the custom command to re-run whenever the executable is recompiled" [1]

This patch adds a DEPENDS argument to both add_custom_command invocations so that the archives also have a file-level dependency on the target they are merging with. That way, changes in say, libunwind source code, will be updated in the libc++abi and/or libc++ static libraries as well.

[1] https://cmake.org/cmake/help/v3.20/command/add_custom_command.html

Differential Revision: https://reviews.llvm.org/D98129
2021-03-18 18:51:10 +01:00
Nico Weber 72b18a86e1 [libcxxabi] Fewer assumptions about path from libcxx to libcxxabi
This is useful for projects that pull in libcxx and libcxxabi and build
them using out-of-tree build files, but don't make them sibling
directories (or don't call the sibling directories libcxx and libcxxabi
for some reason).

Fixes PR49313.

Differential Revision: https://reviews.llvm.org/D97379
2021-02-26 09:10:18 -05:00
Patrick Oppenlander 26a0aeba61 [libc++abi] Add builtins to dynamic library link
Otherwise libc++abi.so fails to link on arm with undefined references to
some __aeabi_ builtins.

Differential Revision: https://reviews.llvm.org/D96574
2021-02-17 17:05:59 -05:00
Zbigniew Sarbinowski 5f9be2c3e3 [SystemZ][ZOS] Prefer -nostdlib++ as opposed to -nodefaultlibs when building c++ libraries
Let's use -nostdlib++ rather than -nodefaultlibs when building libc++/libc++abi/libunwind libraries. The default is -nostdlib++ if supported by a build compiler like it is the case with clang, otherwise -nodefaultlibs is used as before.

This change is needed to avoid additional changes at the link step and not to increase the maintenance costs. If clang with -nodefaultlibs is used all the libraries which are removed but required would have to be manually added in. This set of libraries are unique and will send out.

The propose change will allow to make the link step simple for other platforms as well.

Reviewed By: #libc, #libc_abi, ldionne

Differential Revision: https://reviews.llvm.org/D95875
2021-02-16 18:42:14 +00:00
Marek Kurdej 3b625060fc [libc++] [libc++abi] Use C++20 standard.
This change is needed to use char8_t when building libc++.
Using the same standard in libc++abi for coherence.

See https://reviews.llvm.org/D91517.

Reviewed By: ldionne, #libc, #libc_abi

Differential Revision: https://reviews.llvm.org/D91691
2020-11-22 15:57:25 +01:00
Louis Dionne 8d51969bd4 [runtimes] Avoid overwriting the rpath unconditionally
When building the runtimes, it's very important not to add rpaths unless
the user explicitly asks for them (the standard way being CMAKE_INSTALL_RPATH),
or to change the install name dir unless the user requests it (via
CMAKE_INSTALL_NAME_DIR).

llvm_setup_rpath() would override the install_name_dir of the runtimes
even if CMAKE_INSTALL_NAME_DIR was specified to something, which is wrong
and in fact even "dangerous" for the runtimes.

This issue was discovered when trying to build libc++ and libc++abi as
system libraries for Apple, where we set the install name dir to /usr/lib
explicitly. llvm_setup_rpath() would cause libc++ to have the wrong install
name dir, and for basically everything on the system to fail to load.
This was discovered just now because we previously used something closer
to a standalone build, where llvm_setup_rpath() wouldn't exist, and hence
not be used.

This is a revert of the following commits:

  libunwind: 3a667b9bd8
  libc++abi: 4877063e19
  libc++: 88434fe05f

Those added llvm_setup_rpath() for consistency, so it seems reasonable
to revert.

Differential Revision: https://reviews.llvm.org/D91099
2020-11-09 16:56:03 -05:00
Louis Dionne 1b2fa6e46e [libc++/libc++abi] Use Python3_EXECUTABLE consistently to run utilities 2020-11-02 11:07:31 -05:00
Louis Dionne 2f8dd2687f [libc++] Refactor the run-buildbot script to make it more modular, and run the benchmarks
As a fly-by fix, unbreak the benchmarks on Apple platforms.

Differential Revision: https://reviews.llvm.org/D90043
2020-10-23 15:11:41 -04:00
Louis Dionne 48e4b0fd3a [runtimes] Revert the libc++ __config_site change
This is a massive revert of the following commits (from most revent to oldest):

	2b9b7b5775.
	529ac33197
	28270234f1
	69c2087283
	b5aa67446e
	5d796645d6

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.
2020-10-23 09:41:48 -04:00
Louis Dionne 5d796645d6 [take 2] [libc++] Include <__config_site> from <__config>
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.

This commit was originally applied in 1e46d1aa3 and reverted in eb60c487
because it broke the libc++abi and libunwind test suites. This has now
been fixed.

Differential Revision: https://reviews.llvm.org/D89041
2020-10-21 10:40:33 -04:00
Louis Dionne eb60c48744 [libc++] Revert "Include <__config_site> from <__config>"
This temporarily reverts commit 1e46d1aa until I find a solution to fix
the libc++abi and libunwind test suites with that change.
2020-10-21 09:18:29 -04:00
Louis Dionne 1e46d1aa3f [libc++] Include <__config_site> from <__config>
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/D89041
2020-10-21 08:46:57 -04:00
Louis Dionne 9b40ee8eb0 [libc++] Define new/delete in libc++abi only by default
Previously, we would define new/delete in both libc++ and libc++abi.
Not only does this cause code bloat, but also it's technically an ODR
violation since we don't know which operator will be selected. Furthermore,
since those are weak definitions, we should strive to have as few of them
as possible (to improve load times).

My preferred choice would have been to put the operators in libc++ only
by default, however that would create a circular dependency between
libc++ and libc++abi, which GNU linkers don't handle.

Folks who want to ship new/delete in libc++ instead of libc++abi are
free to do so by turning on LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS at
CMake configure time.

On Apple platforms, this shouldn't be an ABI break because we re-export
the new/delete symbols from libc++abi. This change actually makes libc++
behave closer to the system libc++ shipped on Apple platforms.

On other platforms, this is an ABI break for people linking against libc++
but not libc++abi. However, vendors have been consulted in D68269 and no
objection was raised. Furthermore, the definitions can be controlled to
appear in libc++ instead with the CMake option.

Differential Revision: https://reviews.llvm.org/D68269
2020-10-19 11:35:01 -04:00
Louis Dionne d5a6da84a3 [libc++/abi] Revert "[libc++] Move the weak symbols list to libc++abi"
This reverts commit c7d4aa711a. I am still investigating the issue,
but it looks like that commit has an interaction with ld64 that causes
new/delete weak re-exports not to work properly anymore. This is weird
because this commit did not touch the exports of new/delete -- I am
still investigating.
2020-10-05 11:42:13 -04:00
Louis Dionne c7d4aa711a [libc++] Move the weak symbols list to libc++abi
Those symbols are exported from libc++abi in the first place, so it
makes more sense to have them there.
2020-10-02 09:22:23 -04:00
Louis Dionne 8654a0f8bb [libc++] Don't re-export new/delete from libc++abi when they are defined in libc++
This is a temporary workaround until the new/delete situation is made
better (i.e. we don't include new/delete in both libc++ and libc++abi
by default).
2020-10-01 13:31:55 -04:00
Louis Dionne 4f13b99929 [libc++] Simplify how we re-export symbols from libc++abi
Instead of managing two copies of the symbol lists, reuse the same list
in libc++abi and libc++.

Differential Revision: https://reviews.llvm.org/D88623
2020-10-01 08:30:27 -04:00
Louis Dionne aae2ff645b [libc++abi] Also build the static archive with C++17
The dylib and the static archive should really be built using the same
Standard, it was just an oversight.
2020-07-23 12:40:19 -04:00
Louis Dionne e3650dc979 [libc++abi] Build the dylib with C++17, like for libc++ 2020-07-23 11:35:41 -04:00
Nico Weber 1afd889d0b [gn build] Make sync_source_lists_from_cmake handle one-line sources lines
sync_source_lists_from_cmake now also looks for source files in
`sources += [ "foo.cc" ]` lines, which allows us to remove most
`# Make `gn format` not collapse this` comments.

(sync_source_lists_from_cmake doesn't look for `foo_headers += [...]`
still, so the comment is still needed in two places for that.)

No intentional behavior change.
2020-07-17 11:53:42 -04:00
Louis Dionne 9c795481e2 [libc++abi] Remove empty source file cxa_unexpected.cpp 2020-06-30 11:18:26 -04:00
Louis Dionne 6f6c8a2d96 [libc++abi] Make sure we link in CrashReporterClient.a when it's present
When building the system libc++abi for Apple, we use CrashReporterClient
to provide better crash logs when calling abort(). This is exemplified by
the fact that we test for the presence of <CrashReporterClient.h> in
abort_message.cpp.

However, we must link against CrashReporterClient.a in order to get that
functionality, otherwise we get a linking error.
2020-06-02 12:23:53 -04:00
Louis Dionne e5291c4ae3 [libc++/abi] Provide an option to turn on forgiving dynamic_cast when building libc++abi
Instead of the ad-hoc #define _LIBCXX_DYNAMIC_FALLBACK, provide an option
to enable the setting when building libc++abi. Also use the occasion to
rename the option to something slightly more descriptive.

Note that in the future, it would be great to simply remove this option
altogether. However, in the meantime, it seems better to have it be an
official option than something ad-hoc.
2020-04-22 16:24:26 -04:00
Louis Dionne ecf313c01d [libc++] Fix the no-exceptions build of libc++ on Apple
We previously tried re-exporting symbols that didn't exist when
exceptions were disabled. Note that building libc++abi without
exceptions still doesn't work when linking against the default-provided
libSystem.dylib, because it transitively depends on libobjc.dylib,
and that requires __gxx_personality_v0. But building libc++abi
with exceptions and libc++ without exceptions does work.
2020-04-20 10:45:14 -04:00
Louis Dionne e9271a494f Remove legacy CMake targets for libcxx and libcxxabi
We've been meaning to remove those targets for a while, and the fix is
simple enough cause they're all just aliases to other targets.

This is a re-application of f383fb40b1, wich was reverted in 04d48111b
because the build bots had not been updated yet. The build bot configurations
have now been updated not to use the deprecated targets, and I verified
that they were using the non-deprecated targets, so we should be good
unless I missed a bot.

Differential Revision: https://reviews.llvm.org/D76104
2020-03-30 09:45:21 -04:00
Louis Dionne 04d48111bf Revert "Remove legacy CMake targets for libcxx and libcxxabi"
This reverts commit f383fb40b. It looks like several of our build bots
are still using the legacy target names, so we'll change those before
we commit this change again.
2020-03-23 11:03:00 -04:00
Louis Dionne f383fb40b1 Remove legacy CMake targets for libcxx and libcxxabi
We've been meaning to remove those targets for a while, and the fix is
simple enough cause they're all just aliases to other targets.

There's no doubt this commit will break some CI systems, however the
fix is trivial.

Differential Revision: https://reviews.llvm.org/D76104
2020-03-23 10:51:23 -04:00
Shoaib Meenai 076da521f3 [libcxx] Link against android_support when needed
libc++ on Android needs to be linked against libandroid_support on API
levels less than 21 to provide needed functions that aren't in the libc
on those platforms (e.g. posix_memalign for libcxxabi). libc++ from the
NDK is a linker script that pulls in libandroid_support, but for
building libc++ itself, we need to explicitly add libandroid_support as
a dependency. Moreover, libc++ headers reference the functions provided
by libandroid_support, so it needs to be added as a public dependency.

Differential Revision: https://reviews.llvm.org/D73516
2020-01-28 14:36:24 -08:00
Kazuaki Ishizaki dac7cda3a8 [libcxxabi] NFC: Fix trivial typos in comments
Reviewers: EricWF, mclow.lists, Jim

Reviewed By: Jim

Subscribers: mgorny, christof, ldionne, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D72151
2020-01-22 11:36:31 +08:00
Louis Dionne be52ff9506 [libc++abi] Introduce a LIBCXXABI_LIBRARY_VERSION option
That option controls the 'VERSION' attribute of the libc++abi shared
library, which in turn controls the name of the actual dylib being
produced.

llvm-svn: 373949
2019-10-07 19:22:04 +00:00
Louis Dionne d03068c3e1 [libc++abi] Do not define -Dcxxabi_shared_EXPORTS when building libc++abi
CMake sets adds that definition automatically, but we don't need
or use it.

llvm-svn: 373940
2019-10-07 18:55:15 +00:00
Louis Dionne f385a38140 [libc++abi] Remove redundant link flags on Apple platforms
These flags are already set when we create the cxxabi_shared target
using the SOVERSION and VERSION target properties, and the install_name
was already being overriden to '@rpath/libc++abi.1.dylib' by CMake
because no 'CMAKE_INSTALL_NAME_DIR' option was specified. So this is
effectively a removal of dead code with no intended functionality change.

The only think we're losing here is that we used to link against
libSystem.B.dylib instead of libSystem.dylib when building libc++abi
for macOS 10.6 -- however, I strongly suspect nobody's building
libc++abi from source for that target anymore.

llvm-svn: 373934
2019-10-07 18:12:10 +00:00
Louis Dionne ce452b1ca9 [libc++abi] Link against libSystem on Apple platforms
On Apple platforms, libSystem is an umbrella for all other system
libraries, and libpthread (and friends) are actually just symlinks
to libSystem.

llvm-svn: 373770
2019-10-04 18:32:46 +00:00
Adhemerval Zanella 6023cf2234 [libcxxabi] Fix arm build failer with libgcc
Both arm32 armv7/armv8 bots which do not use compiler-rt are failing
to a linking issue:

[100%] Built target cxxabi_static
CMakeFiles/cxxabi_shared.dir/cxa_demangle.cpp.o: In function `(anonymous namespace)::itanium_demangle::OutputStream::writeUnsigned(unsigned long long, bool)':
/home/buildslave/buildslave/libcxx-libcxxabi-libunwind-armv7-linux-noexceptions/llvm/projects/libcxxabi/src/demangle/Utility.h:55: undefined reference to `__aeabi_uldivmod'
/home/buildslave/buildslave/libcxx-libcxxabi-libunwind-armv7-linux-noexceptions/llvm/projects/libcxxabi/src/demangle/Utility.h:56: undefined reference to `__aeabi_uldivmod'
clang-6.0: error: linker command failed with exit code 1 (use -v to see invocation)

It seems after r371273 OutputStream is used more extensively and
is pulling OutputStream::writeUnsigned (which thus requires unsigned
integer module).

The straightfoward fix is to explicit link against libgcc if
compiler-rt is not used.

llvm-svn: 372921
2019-09-25 21:46:24 +00:00
Louis Dionne 0a06eb911b [libc++] Take 2: Integrate the PSTL into libc++
Summary:
This commit allows specifying LIBCXX_ENABLE_PARALLEL_ALGORITHMS when
configuring libc++ in CMake. When that option is enabled, libc++ will
assume that the PSTL can be found somewhere on the CMake module path,
and it will provide the C++17 parallel algorithms based on the PSTL
(that is assumed to be available).

The commit also adds support for running the PSTL tests as part of
the libc++ test suite.

The first attempt to commit this failed because it exposed a bug in the
tests for modules. Now that this has been fixed, it should be safe to
commit this.

Reviewers: EricWF

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits, mclow.lists, EricWF

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60480

llvm-svn: 367903
2019-08-05 18:29:14 +00:00
Louis Dionne a3c83b7511 Revert "[libc++] Integrate the PSTL into libc++"
This reverts r366593, which caused unforeseen breakage on the build bots.
I'm reverting until the problems have been figured out and fixed.

llvm-svn: 366603
2019-07-19 18:52:46 +00:00
Louis Dionne 910323e667 [libc++] Integrate the PSTL into libc++
Summary:
This commit allows specifying LIBCXX_ENABLE_PARALLEL_ALGORITHMS when
configuring libc++ in CMake. When that option is enabled, libc++ will
assume that the PSTL can be found somewhere on the CMake module path,
and it will provide the C++17 parallel algorithms based on the PSTL
(that is assumed to be available).

The commit also adds support for running the PSTL tests as part of
the libc++ test suite.

Reviewers: rodgert, EricWF

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits, mclow.lists, EricWF

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60480

llvm-svn: 366593
2019-07-19 17:02:42 +00:00
Louis Dionne 223df5b540 [libcxxabi] Use an explicit list to export symbols from the dylib
Reviewers: EricWF

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D63345

llvm-svn: 364586
2019-06-27 20:17:22 +00:00
Petr Hosek 737de4d363 [libcxx] Use libtool when merging archives on Apple platforms
ar doesn't produce the correct results when used for linking static
archives on Apple platforms, so instead use libtool -static which is
the official way to build static archives on those platforms.

Differential Revision: https://reviews.llvm.org/D62770

llvm-svn: 362311
2019-06-02 01:14:31 +00:00
Petr Hosek 81f433b48c [runtimes] Move libunwind, libc++abi and libc++ to lib/$target/c++ and include/c++
This change is a consequence of the discussion in "RFC: Place libs in
Clang-dedicated directories", specifically the suggestion that
libunwind, libc++abi and libc++ shouldn't be using Clang resource
directory. Tools like clangd make this assumption, but this is
currently not true for the LLVM_ENABLE_PER_TARGET_RUNTIME_DIR build.
This change addresses that by moving the output of these libraries to
lib/$target/c++ and include/c++ directories, leaving resource directory
only for compiler-rt runtimes and Clang builtin headers.

Differential Revision: https://reviews.llvm.org/D59168

llvm-svn: 361432
2019-05-22 21:08:33 +00:00
Nico Weber 7399ad3193 minor cmake formatting style fix
llvm-svn: 360142
2019-05-07 13:14:14 +00:00
Petr Hosek 6971a166d9 [libcxxabi] Don't use -fvisibility-global-new-delete-hidden when not defining them
When builing the hermetic static library, the compiler switch
-fvisibility-global-new-delete-hidden is necessary to get the new and
delete operator definitions made correctly. However, when those
definitions are not included in the library, then this switch does harm.
With lld (though not all linkers) setting STV_HIDDEN on SHN_UNDEF
symbols makes it an error to leave them undefined or defined via dynamic
linking that should generate PLTs for -shared linking (lld makes this a
hard error even without -z defs). Though leaving the symbols undefined
would usually work in practice if the linker were to allow it (and the
user didn't pass -z defs), this actually indicates a real problem that
could bite some target configurations more subtly at runtime. For
example, x86-32 ELF -fpic code generation uses hidden visibility on
declarations in the caller's scope as a signal that the call will never
be resolved to a PLT entry and so doesn't have to meet the special ABI
requirements for PLT calls (setting %ebx). Since these functions might
actually be resolved to PLT entries at link time (we don't know what the
user is linking in when the hermetic library doesn't provide all the
symbols itself), it's not safe for the compiler to treat their
declarations at call sites as having hidden visibility.

Differential Revision: https://reviews.llvm.org/D61572

llvm-svn: 360004
2019-05-06 01:25:31 +00:00
Petr Hosek 4fe63c70c7 [gn] Support for building libcxxabi
This change introduces support for building libcxxabi. The library
build should be complete, but not all CMake options have been
replicated in GN. We also don't support tests yet.

We only support two stage build at the moment.

Differential Revision: https://reviews.llvm.org/D60372

llvm-svn: 359805
2019-05-02 17:29:39 +00:00
Petr Hosek 4252555753 [libc++abi] Do not share an object library to create the static/shared libraries
This change is similar to r356150, with the same motivation. The
only difference is that the method used to merge libunwind.a and
libc++abi.a had to be changed to use the same approach as libc++
since we no longer produce object libraries that could be linked
together as we did before. We reuse the libc++ script for merging
archives to avoid duplication between the two projects.

Differential Revision: https://reviews.llvm.org/D60173

llvm-svn: 357635
2019-04-03 20:59:28 +00:00
Sam Clegg 31d7394dc7 [libc++abi] Add LIBCXXABI_ENABLE_PIC cmake option
This is on by default, since on many platforms and configurations
libc++abi.a gets statically linked into shared libraries and/or
PIE executables.

This change is a followup to https://reviews.llvm.org/D60005 which
allows us to default to PIC code, but disable this if needed (for
example on WebAssembly where PIC code its currently compatible with
static linking).

Differential Revision: https://reviews.llvm.org/D60049

llvm-svn: 357551
2019-04-03 00:34:12 +00:00