cmake/modules/CheckAtomic.cmake

   1 # atomic builtins are required for threading support.
   2
   3 INCLUDE(CheckCXXSourceCompiles)
   4
   5 check_function_exists(__atomic_fetch_add_4 HAVE___ATOMIC_FETCH_ADD_4)
   6 if( NOT HAVE___ATOMIC_FETCH_ADD_4 )
   7   check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
   8   set(HAVE_LIBATOMIC False)
   9   if( HAVE_LIBATOMIC )
  10     list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
  11   endif()
  12 endif()
  13
  14 CHECK_CXX_SOURCE_COMPILES("
  15 #ifdef _MSC_VER
  16 #include <Intrin.h> /* Workaround for PR19898. */
  17 #include <windows.h>
  18 #endif
  19 int main() {
  20 #ifdef _MSC_VER
  21         volatile LONG val = 1;
  22         MemoryBarrier();
  23         InterlockedCompareExchange(&val, 0, 1);
  24         InterlockedIncrement(&val);
  25         InterlockedDecrement(&val);
  26 #else
  27         volatile unsigned long val = 1;
  28         __sync_synchronize();
  29         __sync_val_compare_and_swap(&val, 1, 0);
  30         __sync_add_and_fetch(&val, 1);
  31         __sync_sub_and_fetch(&val, 1);
  32 #endif
  33         return 0;
  34       }
  35 " LLVM_HAS_ATOMICS)
  36
  37 if( NOT LLVM_HAS_ATOMICS )
  38   message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
  39 endif()