llvm/cmake/modules/CheckAtomic.cmake
Evgeniy Stepanov 6354451c6a Add CMake check for libatomic.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217666 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-12 11:08:59 +00:00

35 lines
901 B
CMake

# atomic builtins are required for threading support.
INCLUDE(CheckCXXSourceCompiles)
check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
if (HAVE_LIBATOMIC)
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
endif()
CHECK_CXX_SOURCE_COMPILES("
#ifdef _MSC_VER
#include <windows.h>
#endif
int main() {
#ifdef _MSC_VER
volatile LONG val = 1;
MemoryBarrier();
InterlockedCompareExchange(&val, 0, 1);
InterlockedIncrement(&val);
InterlockedDecrement(&val);
#else
volatile unsigned long val = 1;
__sync_synchronize();
__sync_val_compare_and_swap(&val, 1, 0);
__sync_add_and_fetch(&val, 1);
__sync_sub_and_fetch(&val, 1);
#endif
return 0;
}
" LLVM_HAS_ATOMICS)
if( NOT LLVM_HAS_ATOMICS )
message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
endif()