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[LLVM][MIPS] Introduce 64 bit atomic check in CheckAtomic.cmake 

Patch by Nitesh Jain.

Summary: On some target like MIPS32 we need to explicitly link atomic library for 64 bit atomic operations. This module then can be used in LLDB (http://reviews.llvm.org/D20464) or Libcxx (http://reviews.llvm.org/D16613) for explicitly link to atomic library.

Reviewers: chandlerc, beanz
Differential: reviews.llvm.org/D20896
llvm-svn: 273534
This commit is contained in:
Sagar Thakur 2016-06-23 06:39:35 +00:00
parent 79f53ca0b5
commit 9e1de09905
1 changed files with 37 additions and 0 deletions
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37
llvm/cmake/modules/CheckAtomic.cmake
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@ -18,6 +18,22 @@ int main() {
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)
@ -38,6 +54,27 @@ if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
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.