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6487c3b012
When libcxx is built in tree for a host which requires libatomic, LLVM's configuration steps will determine it is required and add it to CMAKE_REQUIRED_LIBRARIES. When libcxx is later configured, it tests if it has C++ atomics without libatomic. The test erroneously passes as libatomic is already part of the set of required libraries. In turn, a number of the atomic tests will fail as they require libatomic but the test suite is configured not to use libatomic. Address this by always dropping libatomic from the set of required libraries before determining if LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB is true, then restoring the set of required libraries. Reviewers: EricWF Differential Revision: https://reviews.llvm.org/D43509 llvm-svn: 329167
55 lines
2.3 KiB
CMake
55 lines
2.3 KiB
CMake
INCLUDE(CheckCXXSourceCompiles)
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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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#
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# We could modify LLVM's CheckAtomic module and have it check for 64-bit
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# atomics instead. However, we would like to avoid careless uses of 64-bit
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# atomics inside LLVM over time on 32-bit platforms.
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function(check_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} -nodefaultlibs -std=c++11 -nostdinc++ -isystem ${LIBCXX_SOURCE_DIR}/include")
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if (${LIBCXX_GCC_TOOLCHAIN})
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set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --gcc-toolchain=${LIBCXX_GCC_TOOLCHAIN}")
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endif()
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if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
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set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
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endif()
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if (CMAKE_C_FLAGS MATCHES -fsanitize-coverage OR CMAKE_CXX_FLAGS MATCHES -fsanitize-coverage)
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set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize-coverage=edge,trace-cmp,indirect-calls,8bit-counters")
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endif()
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check_cxx_source_compiles("
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#include <cstdint>
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#include <atomic>
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std::atomic<uintptr_t> x;
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std::atomic<uintmax_t> y;
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int main() {
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return x + y;
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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_cxx_atomics)
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# Perform the check for 64bit atomics without libatomic. It may have been
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# added to the required libraries during in the configuration of LLVM, which
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# would cause the check for CXX atomics without libatomic to incorrectly pass.
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set(OLD_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
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list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "atomic")
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check_cxx_atomics(LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB)
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set(CMAKE_REQUIRED_LIBRARIES ${OLD_CMAKE_REQUIRED_LIBRARIES})
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check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
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# If not, check if the library exists, and atomics work with it.
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if(NOT LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB)
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if(LIBCXX_HAS_ATOMIC_LIB)
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list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
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check_cxx_atomics(LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB)
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if (NOT LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB)
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message(WARNING "Host compiler must support std::atomic!")
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endif()
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else()
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message(WARNING "Host compiler appears to require libatomic, but cannot find it.")
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endif()
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endif()
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