`CheckAtomic.cmake` was skipping the test of whether atomics work in MSVC
without an atomics library (they do), but not setting the value of
`HAVE_CXX_ATOMICS_WITHOUT_LIB`. That caused build issues when trying to land
D69869. I fixed that issue in f128f442a3, by adding an `elseif(MSVC)`, as
was being done below in the 64-bit atomics check. That minimal fix did work,
but it kept various inconsistencies between the original atomics check and
the 64-bit one. This patch now makes the checks follow the same structure,
cleaning them up.
Differential Revision: https://reviews.llvm.org/D74767
The check for 'HAVE_CXX_ATOMICS_WITHOUT_LIB' may create false
positives in RISC-V. This is reproducible when compiling LLVM natively
using GCC on a rv64gc (rv64imafdgc) host. Due to the 'A' (atomic)
extension, g++ replaces calls to libatomic operations on the
std::atomic<int> type with the native hardware instructions. As a
result, the compilation succeeds and the build system thinks it
doesn't need to pass '-latomic'.
Improve the reliability of the 'HAVE_CXX_ATOMICS_WITHOUT_LIB' test in
two steps:
1. Force a pre-increment on x (++x), which should force a call to a
libatomic function;
2. Because step 1 would resolve the increment to 'amoadd.w.aq' under
the 'A' extension, force the same operation on sub-word types, for
which there is no hardware support.
Reviewers: jfb, hintonda, smeenai, mgorny, JDevlieghere, jyknight
Reviewed By: jfb
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D68964
We were skipping the libatomic requirement check for MSVC, but not setting
the corresponding variable, HAVE_CXX_ATOMICS_WITHOUT_LIB. D69869 seems to
have to failed to build on ARM MSVC because of that, and was reverted. This
should probably fix the issue. The plan is to check the result of the build
bots and then submit a more thoroughly refactored version for review.
Summary:
Always respect existing CMAKE_REQUIRED_FLAGS when adding
additional ones. This is important when cross compiling where
--sysroot and -target were already added.
In particular, this is needed when cross compiling from Darwin to
Linux, since --sysroot is required to find headers and libraries.
Cmake has a similar bug in check_include_file[_cxx] where
CMAKE_REQUIRED_LIBRARIES isn't passed, which causes
try_compile to fail.
(please see https://gitlab.kitware.com/cmake/cmake/merge_requests/1620)
Reviewers: compnerd, silvas, beanz, brad.king
Reviewed By: compnerd
Subscribers: mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D41568
llvm-svn: 321434
The header include was required to work around PR19898, as noted in that
comment. That PR has since been marked resolved fixed, and the
configuration check passes without the header inclusion both when
compiling on Windows with cl and when cross-compiling on Linux using
clang-cl.
I noticed this because the inclusion was cased incorrectly (Intrin.h
instead of intrin.h), which when cross-compiling on a case sensitive
file system would cause the intrin.h from the Windows SDK to be included
(which LLVM can't handle) instead of the one from clang's resource
directory, making the check fail. This is the same issue as r309980.
Correcting the case of the inclusion makes the check pass when cross
compiling, but it seems better to get rid of the inclusion entirely,
since it appears to be unnecessary now.
Differential Revision: https://reviews.llvm.org/D40910
llvm-svn: 319917
Patch by Nitesh Jain.
Summary: On some target like MIPS32 we need to explicitly link atomic library for 64 bit atomic operations. This module then can be used in LLDB (http://reviews.llvm.org/D20464) or Libcxx (http://reviews.llvm.org/D16613) for explicitly link to atomic library.
Reviewers: chandlerc, beanz
Differential: reviews.llvm.org/D20896
llvm-svn: 273534
The cmake check for whether libatomic could be used had been
unconditionally setting the result to false. Which was somewhat
fortunate, because the prerequisite check for whether it was *needed*
was always claiming it was, even if it was not.
However, this made platforms where libatomic is actually necessary
fail to link.
Differential Revision: http://reviews.llvm.org/D10453
llvm-svn: 239819
It is possible for the atomic routines to be provided by the compiler without
requiring any additional libraries. Check if that is the case before checking
for a library.
Patch by Matt Glazar!
llvm-svn: 230452
Luís Marques