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# atomic builtins are required for threading support.
INCLUDE(CheckCXXSourceCompiles)
check_function_exists(__atomic_fetch_add_4 HAVE___ATOMIC_FETCH_ADD_4)
if( NOT HAVE___ATOMIC_FETCH_ADD_4 )
check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
set(HAVE_LIBATOMIC False)
if( HAVE_LIBATOMIC )
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
endif()
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()
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