FYI, this change and the LLVM version have each broken my libcxx
builds. I cross compile from Linux x64 to Hexagon, and my host machine
doesn't have <atomic>. The LLVM change was particularly offensive
because I wasn't planning on building LLVM itself.
I have since worked around the issue by making my cmake invocation longer.
I'm not sure what you can do for the LLVM check, but if you can use the
libcxx headers directly for the <atomic> check, while still using all
the custom flags and tools that I pass on the command line, then I
should be able to remove the explicit setting of
"LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB" in the future.
On 2/16/2016 2:09 PM, Vasileios Kalintiris via cfe-commits wrote:
Hi Hans,
Or is this comment on PR26059 all that needs to be done for 3.8?
That's correct. I wrote that comment in order to clarify which bits we should
merge in 3.8.
The latest commit:
- [libcxx] r260961 - Issue a warning instead of fatal errors when checks for
libatomic fail."
makes sure that my changes don't break older configurations that used to work
previously, by emitting a warning message instead of a fatal error.
I had to turn the error to warning because there are cases where the host compiler doesn't
provide the <cstdint> and <atomic> headers when bootstrapping llvm.
The correct solution would be to use the headers provided from libc++ itself.
However, I wanted to take the safe route for the 3.8 branch and provide the
elegant solution on the trunk after having the proper discussion with the
libc++ devs.
Thanks,
Vasileios
________________________________________
From: hwennb...@google.com [hwennb...@google.com] on behalf of Hans Wennborg
[h...@chromium.org]
Sent: 16 February 2016 19:53
To: Vasileios Kalintiris
Cc: Eric Fiselier; Daniel Sanders; mclow.li...@gmail.com;
cfe-commits@lists.llvm.org
Subject: Re: [libcxx] r260235 - Introduce a cmake module to figure out whether
we need to link with libatomic.
Or is this comment on PR26059 all that needs to be done for 3.8?
"Bug 26369, which has been fixed with r260961, requires the following
commits to get merged on the release branch:
- [libcxx] r260515 - Re-commit "Introduce a cmake module to figure out
whether we need to link with libatomic."
- [libcxx] r260524 - Fix r260515 - Correct typos in CMake changes
- [libcxx] r260531 - Rename CheckLibcxxAtomic.cmake variable result
names so they don't clash with LLVM
- [libcxx] r260961 - Issue a warning instead of fatal errors when
checks for libatomic fail."
Thanks,
Hans
On Tue, Feb 16, 2016 at 11:47 AM, Hans Wennborg <h...@chromium.org> wrote:
Do I understand correctly that there are still issues here's that are not fixed?
(I'm trying to understand if there is something here to merge for 3.8,
but I'm having trouble following these commits.)
On Tue, Feb 16, 2016 at 6:44 AM, Vasileios Kalintiris
<vasileios.kalinti...@imgtec.com> wrote:
I changed the type of message from fatal_error to warning in r260961. While
the test for atomics works fine in most cases, it fails because we include
<cstdint> and <atomic>, and the user's host compiler might not provide them
during a bootstrap (see PR26631 and PR26622).
Does anyone have any idea how to tackle this problem? As suggested by the
bug reports, we could include the headers provided by libc++. However, I'm
not sure whether we are supposed to do that during configuration time.
- Vasileios
________________________________
From: Eric Fiselier [e...@efcs.ca]
Sent: 11 February 2016 16:08
To: Daniel Sanders
Cc: Vasileios Kalintiris; h...@chromium.org; mclow.li...@gmail.com;
cfe-commits@lists.llvm.org
Subject: Re: [libcxx] r260235 - Introduce a cmake module to figure out
whether we need to link with libatomic.
we need to rename HAVE_CXX_ATOMICS_WITH_LIB to something like
LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB.
Fixed in r260531.
I think we will eventually want to merge the following commits, assuming
they don't regress the build, especially with the -gcc-toolchain option.
- [libcxx] r260515 - Re-commit "Introduce a cmake module to figure out
whether we need to link with libatomic."
- [libcxx] r260524 - Fix r260515 - Correct typos in CMake changes
- [libcxx] r260531 - Rename CheckLibcxxAtomic.cmake variable result names so
they don't clash with LLVM
@Marshall Any objections?
On Thu, Feb 11, 2016 at 2:18 AM, Daniel Sanders via cfe-commits
<cfe-commits@lists.llvm.org> wrote:
Hi,
In my latests rc2+patches build I've also found that we need to rename
HAVE_CXX_ATOMICS_WITH_LIB to something like
LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB. It's currently re-using the result of
LLVM's check which doesn't include 64-bit atomics.
________________________________________
From: Vasileios Kalintiris
Sent: 09 February 2016 23:50
To: h...@chromium.org
Cc: cfe-commits@lists.llvm.org; Daniel Sanders; mclow.li...@gmail.com
Subject: RE: [libcxx] r260235 - Introduce a cmake module to figure out
whether we need to link with libatomic.
Hi Hans,
Please wait before merging this as it breaks LLVM bootstraps when using
the -gcc-toolchain option and the system's default gcc installation does not
provide libatomic. We have to check LIBCXX_GCC_TOOLCHAIN in our test. I'll
create a patch tomorrow and I'll let you know when it's okay to merge them.
In the meantime, I reverted it in r260323.
- Vasileios
________________________________________
From: Vasileios Kalintiris
Sent: 09 February 2016 18:56
To: h...@chromium.org
Cc: cfe-commits@lists.llvm.org; Daniel Sanders; mclow.li...@gmail.com
Subject: RE: [libcxx] r260235 - Introduce a cmake module to figure out
whether we need to link with libatomic.
Hi Hans,
Can we merge this on the 3.8 release branch? It fixes libcxx builds on
MIPS by linking with libatomic when needed. Also, all the x86_64 and ARM
buildbots for libcxx look good.
Thanks,
Vasileios
________________________________________
From: cfe-commits [cfe-commits-boun...@lists.llvm.org] on behalf of
Vasileios Kalintiris via cfe-commits [cfe-commits@lists.llvm.org]
Sent: 09 February 2016 17:00
To: cfe-commits@lists.llvm.org
Subject: [libcxx] r260235 - Introduce a cmake module to figure out whether
we need to link with libatomic.
Author: vkalintiris
Date: Tue Feb 9 11:00:38 2016
New Revision: 260235
URL: http://llvm.org/viewvc/llvm-project?rev=260235&view=rev
Log:
Introduce a cmake module to figure out whether we need to link with
libatomic.
Summary:
This fixes the tests under std/atomics for 32-bit MIPS CPUs where the
8-byte atomic operations call into the libatomic library.
Reviewers: dsanders, mclow.lists, EricWF, jroelofs, joerg
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D16613
Added:
libcxx/trunk/cmake/Modules/CheckLibcxxAtomic.cmake
Modified:
libcxx/trunk/cmake/config-ix.cmake
libcxx/trunk/lib/CMakeLists.txt
libcxx/trunk/test/CMakeLists.txt
libcxx/trunk/test/libcxx/test/target_info.py
libcxx/trunk/test/lit.site.cfg.in
Added: libcxx/trunk/cmake/Modules/CheckLibcxxAtomic.cmake
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/cmake/Modules/CheckLibcxxAtomic.cmake?rev=260235&view=auto
==============================================================================
--- libcxx/trunk/cmake/Modules/CheckLibcxxAtomic.cmake (added)
+++ libcxx/trunk/cmake/Modules/CheckLibcxxAtomic.cmake Tue Feb 9 11:00:38
2016
@@ -0,0 +1,38 @@
+INCLUDE(CheckCXXSourceCompiles)
+
+# Sometimes linking against libatomic is required for atomic ops, if
+# the platform doesn't support lock-free atomics.
+#
+# We could modify LLVM's CheckAtomic module and have it check for 64-bit
+# atomics instead. However, we would like to avoid careless uses of
64-bit
+# atomics inside LLVM over time on 32-bit platforms.
+
+function(check_cxx_atomics varname)
+ set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+ set(CMAKE_REQUIRED_FLAGS "-std=c++11")
+ check_cxx_source_compiles("
+#include <cstdint>
+#include <atomic>
+std::atomic<uintptr_t> x;
+std::atomic<uintmax_t> y;
+int main() {
+ return x + y;
+}
+" ${varname})
+ set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+endfunction(check_cxx_atomics)
+
+check_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB)
+# If not, check if the library exists, and atomics work with it.
+if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
+ check_library_exists(atomic __atomic_fetch_add_8 "" HAVE_LIBATOMIC)
+ if(HAVE_LIBATOMIC)
+ list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
+ check_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB)
+ if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
+ message(FATAL_ERROR "Host compiler must support std::atomic!")
+ endif()
+ else()
+ message(FATAL_ERROR "Host compiler appears to require libatomic, but
cannot find it.")
+ endif()
+endif()
Modified: libcxx/trunk/cmake/config-ix.cmake
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/cmake/config-ix.cmake?rev=260235&r1=260234&r2=260235&view=diff
==============================================================================
--- libcxx/trunk/cmake/config-ix.cmake (original)
+++ libcxx/trunk/cmake/config-ix.cmake Tue Feb 9 11:00:38 2016
@@ -1,5 +1,6 @@
include(CheckLibraryExists)
include(CheckCXXCompilerFlag)
+include(CheckLibcxxAtomic)
# Check compiler flags
@@ -17,3 +18,7 @@ check_library_exists(c fopen "" LIBCXX_H
check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)
check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXX_HAS_GCC_S_LIB)
+
+if (NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
+ set(LIBCXX_HAS_ATOMIC_LIB True)
+endif()
Modified: libcxx/trunk/lib/CMakeLists.txt
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/lib/CMakeLists.txt?rev=260235&r1=260234&r2=260235&view=diff
==============================================================================
--- libcxx/trunk/lib/CMakeLists.txt (original)
+++ libcxx/trunk/lib/CMakeLists.txt Tue Feb 9 11:00:38 2016
@@ -79,6 +79,7 @@ add_library_flags_if(LIBCXX_HAS_C_LIB c)
add_library_flags_if(LIBCXX_HAS_M_LIB m)
add_library_flags_if(LIBCXX_HAS_RT_LIB rt)
add_library_flags_if(LIBCXX_HAS_GCC_S_LIB gcc_s)
+add_library_flags_if(LIBCXX_HAS_ATOMIC_LIB atomic)
# Setup flags.
add_flags_if_supported(-fPIC)
Modified: libcxx/trunk/test/CMakeLists.txt
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/CMakeLists.txt?rev=260235&r1=260234&r2=260235&view=diff
==============================================================================
--- libcxx/trunk/test/CMakeLists.txt (original)
+++ libcxx/trunk/test/CMakeLists.txt Tue Feb 9 11:00:38 2016
@@ -15,6 +15,7 @@ pythonize_bool(LIBCXX_ENABLE_SHARED)
pythonize_bool(LIBCXX_BUILD_32_BITS)
pythonize_bool(LIBCXX_GENERATE_COVERAGE)
pythonize_bool(LIBCXXABI_USE_LLVM_UNWINDER)
+pythonize_bool(LIBCXX_HAS_ATOMIC_LIB)
# The tests shouldn't link to any ABI library when it has been linked
into
# libc++ statically or via a linker script.
Modified: libcxx/trunk/test/libcxx/test/target_info.py
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/libcxx/test/target_info.py?rev=260235&r1=260234&r2=260235&view=diff
==============================================================================
--- libcxx/trunk/test/libcxx/test/target_info.py (original)
+++ libcxx/trunk/test/libcxx/test/target_info.py Tue Feb 9 11:00:38 2016
@@ -172,6 +172,9 @@ class LinuxLocalTI(DefaultTargetInfo):
flags += ['-lunwind', '-ldl']
else:
flags += ['-lgcc_s', '-lgcc']
+ use_libatomic = self.full_config.get_lit_bool('use_libatomic',
False)
+ if use_libatomic:
+ flags += ['-latomic']
san = self.full_config.get_lit_conf('use_sanitizer', '').strip()
if san:
# The libraries and their order are taken from the
Modified: libcxx/trunk/test/lit.site.cfg.in
URL:
http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/lit.site.cfg.in?rev=260235&r1=260234&r2=260235&view=diff
==============================================================================
--- libcxx/trunk/test/lit.site.cfg.in (original)
+++ libcxx/trunk/test/lit.site.cfg.in Tue Feb 9 11:00:38 2016
@@ -20,6 +20,7 @@ config.generate_coverage = "@LIBC
config.target_info = "@LIBCXX_TARGET_INFO@"
config.executor = "@LIBCXX_EXECUTOR@"
config.llvm_unwinder = "@LIBCXXABI_USE_LLVM_UNWINDER@"
+config.use_libatomic = "@LIBCXX_HAS_ATOMIC_LIB@"
# Let the main config do the real work.
lit_config.load_config(config, "@LIBCXX_SOURCE_DIR@/test/lit.cfg")
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