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It is possible for the atomic routines to be provided by the compiler without requiring any additional libraries. Check if that is the case before checking for a library. Patch by Matt Glazar! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230452 91177308-0d34-0410-b5e6-96231b3b80d8
39 lines
1.0 KiB
CMake
39 lines
1.0 KiB
CMake
# atomic builtins are required for threading support.
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INCLUDE(CheckCXXSourceCompiles)
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check_function_exists(__atomic_fetch_add_4 HAVE___ATOMIC_FETCH_ADD_4)
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if( NOT HAVE___ATOMIC_FETCH_ADD_4 )
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check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
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set(HAVE_LIBATOMIC False)
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if( HAVE_LIBATOMIC )
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list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
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endif()
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endif()
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CHECK_CXX_SOURCE_COMPILES("
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#ifdef _MSC_VER
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#include <windows.h>
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#endif
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int main() {
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#ifdef _MSC_VER
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volatile LONG val = 1;
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MemoryBarrier();
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InterlockedCompareExchange(&val, 0, 1);
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InterlockedIncrement(&val);
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InterlockedDecrement(&val);
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#else
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volatile unsigned long val = 1;
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__sync_synchronize();
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__sync_val_compare_and_swap(&val, 1, 0);
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__sync_add_and_fetch(&val, 1);
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__sync_sub_and_fetch(&val, 1);
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#endif
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return 0;
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}
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" LLVM_HAS_ATOMICS)
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if( NOT LLVM_HAS_ATOMICS )
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message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
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endif()
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