diff --git a/cmake/CheckAtomic.cmake b/cmake/CheckAtomic.cmake index b6be817d7d19977fea21a54fe4f32b58ef06abe9..aa118fe61439208def49541aee8f358b4354acec 100644 --- a/cmake/CheckAtomic.cmake +++ b/cmake/CheckAtomic.cmake @@ -49,10 +49,15 @@ elseif(LLVM_COMPILER_IS_GCC_COMPATIBLE OR CMAKE_CXX_COMPILER_ID MATCHES "XL") 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) - 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!") + 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() @@ -65,14 +70,32 @@ elseif(LLVM_COMPILER_IS_GCC_COMPATIBLE OR CMAKE_CXX_COMPILER_ID MATCHES "XL") 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) - 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!") + 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() +# Set variable LLVM_ATOMIC_LIB specifying flags for linking against libatomic. +if(HAVE_CXX_ATOMICS_WITH_LIB OR HAVE_CXX_ATOMICS64_WITH_LIB) + # Use options --push-state, --as-needed and --pop-state if linker is known to support them. + # Use single option -Wl of compiler driver to avoid incorrect re-ordering of options by CMake. + if(LLVM_LINKER_IS_GNULD OR LLVM_LINKER_IS_GOLD OR LLVM_LINKER_IS_LLD OR LLVM_LINKER_IS_MOLD) + set(LLVM_ATOMIC_LIB "-Wl,--push-state,--as-needed,-latomic,--pop-state") + else() + set(LLVM_ATOMIC_LIB "-latomic") + endif() +else() + set(LLVM_ATOMIC_LIB) +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.