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e5a2c5a162
The header include was required to work around PR19898, as noted in that comment. That PR has since been marked resolved fixed, and the configuration check passes without the header inclusion both when compiling on Windows with cl and when cross-compiling on Linux using clang-cl. I noticed this because the inclusion was cased incorrectly (Intrin.h instead of intrin.h), which when cross-compiling on a case sensitive file system would cause the intrin.h from the Windows SDK to be included (which LLVM can't handle) instead of the one from clang's resource directory, making the check fail. This is the same issue as r309980. Correcting the case of the inclusion makes the check pass when cross compiling, but it seems better to get rid of the inclusion entirely, since it appears to be unnecessary now. Differential Revision: https://reviews.llvm.org/D40910 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319917 91177308-0d34-0410-b5e6-96231b3b80d8
107 lines
3.3 KiB
CMake
107 lines
3.3 KiB
CMake
# atomic builtins are required for threading support.
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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 "-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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return 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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uint64_t i = x.load(std::memory_order_relaxed);
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return 0;
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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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## TODO: This define is only used for the legacy atomic operations in
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## llvm's Atomic.h, which should be replaced. Other code simply
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## assumes C++11 <atomic> works.
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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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