cmake/modules/CheckAtomic.cmake

   1 # atomic builtins are required for threading support.
   2
   3 INCLUDE(CheckCXXSourceCompiles)
   4
   5 CHECK_CXX_SOURCE_COMPILES("
   6 #ifdef _MSC_VER
   7 #include <windows.h>
   8 #endif
   9 int main() {
  10 #ifdef _MSC_VER
  11         volatile LONG val = 1;
  12         MemoryBarrier();
  13         InterlockedCompareExchange(&val, 0, 1);
  14         InterlockedIncrement(&val);
  15         InterlockedDecrement(&val);
  16 #else
  17         volatile unsigned long val = 1;
  18         __sync_synchronize();
  19         __sync_val_compare_and_swap(&val, 1, 0);
  20         __sync_add_and_fetch(&val, 1);
  21         __sync_sub_and_fetch(&val, 1);
  22 #endif
  23         return 0;
  24       }
  25 " LLVM_HAS_ATOMICS)
  26
  27 if( NOT LLVM_HAS_ATOMICS )
  28   message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
  29 endif()