diff options
Diffstat (limited to 'cmake/Modules/CheckLibcxxAtomic.cmake')
| -rw-r--r-- | cmake/Modules/CheckLibcxxAtomic.cmake | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/cmake/Modules/CheckLibcxxAtomic.cmake b/cmake/Modules/CheckLibcxxAtomic.cmake new file mode 100644 index 000000000000..4ff343236fea --- /dev/null +++ b/cmake/Modules/CheckLibcxxAtomic.cmake @@ -0,0 +1,41 @@ +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 -nostdinc++ -isystem ${LIBCXX_SOURCE_DIR}/include") + if (${LIBCXX_GCC_TOOLCHAIN}) + set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --gcc-toolchain=${LIBCXX_GCC_TOOLCHAIN}") + endif() + 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(LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB) +check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB) +# If not, check if the library exists, and atomics work with it. +if(NOT LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB) + if(LIBCXX_HAS_ATOMIC_LIB) + list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic") + check_cxx_atomics(LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB) + if (NOT LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB) + message(WARNING "Host compiler must support std::atomic!") + endif() + else() + message(WARNING "Host compiler appears to require libatomic, but cannot find it.") + endif() +endif() |