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Fix atomic for architectures without support for lock-free atomics (e.g. armv6l)

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Artur Sinila 2021-06-29 22:41:25 +03:00
parent 076f815cec
commit 345069028b
WARNING! Although there is a key with this ID in the database it does not verify this commit! This commit is SUSPICIOUS.
GPG key ID: CCC2023706A0FA7E
2 changed files with 100 additions and 0 deletions
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3
CMakeLists.txt
View file

@ -203,6 +203,9 @@ else()
endif()
endif()
include("cmake/atomic.cmake")
list(APPEND mi_libraries ${CMAKE_REQUIRED_LIBRARIES})
# -----------------------------------------------------------------------------
# Install and output names
# -----------------------------------------------------------------------------

97
cmake/atomic.cmake Normal file
View file

@ -0,0 +1,97 @@
# Based on:
# https://github.com/llvm/llvm-project/blob/d4dcb55c7050fd908af2378fa551078d859d994f/llvm/cmake/modules/DetermineGCCCompatible.cmake
# https://github.com/llvm/llvm-project/blob/d4dcb55c7050fd908af2378fa551078d859d994f/llvm/cmake/modules/CheckAtomic.cmake
INCLUDE(CheckCXXSourceCompiles)
INCLUDE(CheckLibraryExists)
# Determine if the compiler has GCC-compatible command-line syntax.
if(CMAKE_COMPILER_IS_GNUCXX)
set(COMPILER_IS_GCC_COMPATIBLE ON)
elseif( MSVC )
set(COMPILER_IS_GCC_COMPATIBLE OFF)
elseif( "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" )
set(COMPILER_IS_GCC_COMPATIBLE ON)
elseif( "${CMAKE_CXX_COMPILER_ID}" MATCHES "Intel" )
set(COMPILER_IS_GCC_COMPATIBLE ON)
endif()
# 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 ${CMAKE_REQUIRED_FLAGS})
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
CHECK_CXX_SOURCE_COMPILES("
#include <atomic>
std::atomic<int> x;
std::atomic<short> y;
std::atomic<char> z;
int main() {
++z;
++y;
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);
(void)i;
return 0;
}
" ${varname})
set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
endfunction(check_working_cxx_atomics64)
# Check for (non-64-bit) atomic operations.
if(MSVC)
set(HAVE_CXX_ATOMICS_WITHOUT_LIB True)
elseif(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)
elseif(COMPILER_IS_GCC_COMPATIBLE)
# First check if atomics work without the library.
check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITHOUT_LIB)
# 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 64-bit std::atomic!")
endif()
else()
message(FATAL_ERROR "Host compiler appears to require libatomic for 64-bit operations, but cannot find it.")
endif()
endif()
endif()