81 lines
2.5 KiB
CMake
81 lines
2.5 KiB
CMake
INCLUDE(CheckCXXSourceCompiles)
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INCLUDE(CheckLibraryExists)
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# Sometimes linking against libatomic is required for atomic ops, if
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# the platform doesn't support lock-free atomics.
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function(check_working_cxx_atomics varname)
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set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
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set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
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CHECK_CXX_SOURCE_COMPILES("
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#include <atomic>
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std::atomic<int> x;
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int main()
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{
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return std::atomic_is_lock_free(&x);
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}
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" ${varname})
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set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
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endfunction(check_working_cxx_atomics)
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function(check_working_cxx_atomics64 varname)
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set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
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set(CMAKE_REQUIRED_FLAGS "-std=c++11 ${CMAKE_REQUIRED_FLAGS}")
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CHECK_CXX_SOURCE_COMPILES("
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#include <atomic>
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#include <cstdint>
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std::atomic<uint64_t> x (0);
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int main()
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{
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uint64_t i = x.load(std::memory_order_relaxed);
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return std::atomic_is_lock_free(&x);
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}
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" ${varname})
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set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
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endfunction(check_working_cxx_atomics64)
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# This isn't necessary on MSVC, so avoid command-line switch annoyance
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# by only running on GCC-like hosts.
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if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
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# First check if atomics work without the library.
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check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB)
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# If not, check if the library exists, and atomics work with it.
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if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
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check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
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if( HAVE_LIBATOMIC )
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list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
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check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB)
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if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
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message(FATAL_ERROR "Host compiler must support std::atomic!")
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endif()
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else()
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message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
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endif()
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endif()
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endif()
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# Check for 64 bit atomic operations.
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if(MSVC)
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set(HAVE_CXX_ATOMICS64_WITHOUT_LIB True)
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else()
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check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITHOUT_LIB)
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endif()
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# If not, check if the library exists, and atomics work with it.
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if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
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check_library_exists(atomic __atomic_load_8 "" HAVE_CXX_LIBATOMICS64)
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if(HAVE_CXX_LIBATOMICS64)
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list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
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check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITH_LIB)
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if (NOT HAVE_CXX_ATOMICS64_WITH_LIB)
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message(FATAL_ERROR "Host compiler must support std::atomic!")
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endif()
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else()
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message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
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endif()
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endif()
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