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Merge pull request #5436

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yangfl (1):
      chore(cmake): check for libatomic support
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sudden6 2018-11-19 13:26:37 +01:00
commit 6ca901f936
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2 changed files with 108 additions and 0 deletions
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2
CMakeLists.txt
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@ -80,6 +80,8 @@ if (UNIX AND NOT APPLE)
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,-z,relro") set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,-z,relro")
endif() endif()
include(CheckAtomic)
# Use ccache when available to speed up builds. # Use ccache when available to speed up builds.
if (USE_CCACHE) if (USE_CCACHE)

106
cmake/CheckAtomic.cmake Normal file
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@ -0,0 +1,106 @@
# atomic builtins are required for threading support.
INCLUDE(CheckCXXSourceCompiles)
# Sometimes linking against libatomic is required for atomic ops, if
# the platform doesn't support lock-free atomics.
function(check_working_cxx_atomics varname)
set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
set(CMAKE_REQUIRED_FLAGS "-std=c++11")
CHECK_CXX_SOURCE_COMPILES("
#include <atomic>
std::atomic<int> x;
int main() {
return x;
}
" ${varname})
set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
endfunction(check_working_cxx_atomics)
function(check_working_cxx_atomics64 varname)
set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
set(CMAKE_REQUIRED_FLAGS "-std=c++11 ${CMAKE_REQUIRED_FLAGS}")
CHECK_CXX_SOURCE_COMPILES("
#include <atomic>
#include <cstdint>
std::atomic<uint64_t> x (0);
int main() {
uint64_t i = x.load(std::memory_order_relaxed);
return 0;
}
" ${varname})
set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
endfunction(check_working_cxx_atomics64)
# This isn't necessary on MSVC, so avoid command-line switch annoyance
# by only running on GCC-like hosts.
if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
# First check if atomics work without the library.
check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB)
# If not, check if the library exists, and atomics work with it.
if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
if( HAVE_LIBATOMIC )
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB)
if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
message(FATAL_ERROR "Host compiler must support std::atomic!")
endif()
else()
message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
endif()
endif()
endif()
# Check for 64 bit atomic operations.
if(MSVC)
set(HAVE_CXX_ATOMICS64_WITHOUT_LIB True)
else()
check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITHOUT_LIB)
endif()
# If not, check if the library exists, and atomics work with it.
if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
check_library_exists(atomic __atomic_load_8 "" HAVE_CXX_LIBATOMICS64)
if(HAVE_CXX_LIBATOMICS64)
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITH_LIB)
if (NOT HAVE_CXX_ATOMICS64_WITH_LIB)
message(FATAL_ERROR "Host compiler must support std::atomic!")
endif()
else()
message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
endif()
endif()
## TODO: This define is only used for the legacy atomic operations in
## llvm's Atomic.h, which should be replaced. Other code simply
## assumes C++11 <atomic> works.
CHECK_CXX_SOURCE_COMPILES("
#ifdef _MSC_VER
#include <Intrin.h> /* Workaround for PR19898. */
#include <windows.h>
#endif
int main() {
#ifdef _MSC_VER
volatile LONG val = 1;
MemoryBarrier();
InterlockedCompareExchange(&val, 0, 1);
InterlockedIncrement(&val);
InterlockedDecrement(&val);
#else
volatile unsigned long val = 1;
__sync_synchronize();
__sync_val_compare_and_swap(&val, 1, 0);
__sync_add_and_fetch(&val, 1);
__sync_sub_and_fetch(&val, 1);
#endif
return 0;
}
" LLVM_HAS_ATOMICS)
if( NOT LLVM_HAS_ATOMICS )
message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
endif()