57 lines
1.8 KiB
CMake
57 lines
1.8 KiB
CMake
# Original issue:
|
||
# * https://gitlab.kitware.com/cmake/cmake/-/issues/23021#note_1098733
|
||
#
|
||
# For reference:
|
||
# * https://gcc.gnu.org/wiki/Atomic/GCCMM
|
||
#
|
||
# riscv64 specific:
|
||
# * https://lists.debian.org/debian-riscv/2022/01/msg00009.html
|
||
#
|
||
# ATOMICS_FOUND - system has c++ atomics
|
||
# ATOMICS_LIBRARIES - libraries needed to use c++ atomics
|
||
# ATOMICS_LIBRARY_FLAGS - flags required to link with c++ atomics library
|
||
|
||
include(CheckCXXSourceCompiles)
|
||
|
||
# RISC-V only has 32-bit and 64-bit atomic instructions. GCC is supposed
|
||
# to convert smaller atomics to those larger ones via masking and
|
||
# shifting like LLVM, but it’s a known bug that it does not. This means
|
||
# anything that wants to use atomics on 1-byte or 2-byte types needs
|
||
# -latomic, but not 4-byte or 8-byte (though it does no harm).
|
||
set(atomic_code
|
||
"
|
||
#include <atomic>
|
||
#include <cstdint>
|
||
std::atomic<uint8_t> n8 (0); // riscv64
|
||
std::atomic<uint64_t> n64 (0); // armel, mipsel, powerpc
|
||
int main() {
|
||
++n8;
|
||
++n64;
|
||
return 0;
|
||
}")
|
||
|
||
check_cxx_source_compiles("${atomic_code}" ATOMICS_LOCK_FREE_INSTRUCTIONS)
|
||
|
||
if (ATOMICS_LOCK_FREE_INSTRUCTIONS)
|
||
set(ATOMICS_FOUND TRUE)
|
||
set(ATOMICS_LIBRARIES)
|
||
set(ATOMICS_LIBRARY_FLAGS)
|
||
else()
|
||
set(CMAKE_REQUIRED_LIBRARIES "-latomic")
|
||
check_cxx_source_compiles("${atomic_code}" ATOMICS_IN_LIBRARY)
|
||
set(CMAKE_REQUIRED_LIBRARIES)
|
||
if (ATOMICS_IN_LIBRARY)
|
||
set(ATOMICS_LIBRARY atomic)
|
||
include(FindPackageHandleStandardArgs)
|
||
find_package_handle_standard_args(Atomics DEFAULT_MSG ATOMICS_LIBRARY)
|
||
set(ATOMICS_LIBRARIES ${ATOMICS_LIBRARY})
|
||
set(ATOMICS_LIBRARY_FLAGS "-latomic")
|
||
unset(ATOMICS_LIBRARY)
|
||
else()
|
||
if (Atomics_FIND_REQUIRED)
|
||
message(FATAL_ERROR "Neither lock free instructions nor -latomic found.")
|
||
endif()
|
||
endif()
|
||
endif()
|
||
unset(atomic_code)
|