diff options
Diffstat (limited to 'third_party/highway/cmake/FindAtomics.cmake')
| -rw-r--r-- | third_party/highway/cmake/FindAtomics.cmake | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/third_party/highway/cmake/FindAtomics.cmake b/third_party/highway/cmake/FindAtomics.cmake new file mode 100644 index 0000000000..e866b73fac --- /dev/null +++ b/third_party/highway/cmake/FindAtomics.cmake @@ -0,0 +1,56 @@ +# 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 + +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; + }") + +# https://gitlab.kitware.com/cmake/cmake/-/issues/24063 +set(CMAKE_CXX_STANDARD 11) +check_cxx_source_compiles("${atomic_code}" ATOMICS_LOCK_FREE_INSTRUCTIONS) + +if(ATOMICS_LOCK_FREE_INSTRUCTIONS) + set(ATOMICS_FOUND TRUE) + set(ATOMICS_LIBRARIES) +else() + set(CMAKE_REQUIRED_LIBRARIES "-latomic") + check_cxx_source_compiles("${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}) + unset(ATOMICS_LIBRARY) + else() + if(Atomics_FIND_REQUIRED) + message(FATAL_ERROR "Neither lock free instructions nor -latomic found.") + endif() + endif() +endif() +unset(atomic_code) +unset(CMAKE_CXX_STANDARD) |