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# ==============================================================================
# LLVM Release License
# ==============================================================================
# University of Illinois/NCSA Open Source License
#
# Copyright (c) 2003-2018 University of Illinois at Urbana-Champaign. All rights
# reserved.
#
# Developed by:
#
# LLVM Team
#
# University of Illinois at Urbana-Champaign
#
# http://llvm.org
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# with the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# * Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimers.
#
# * Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimers in the documentation
# and/or other materials provided with the distribution.
#
# * Neither the names of the LLVM Team, University of Illinois at
# Urbana-Champaign, nor the names of its contributors may be used to endorse
# or promote products derived from this Software without specific prior
# written permission.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH
# THE SOFTWARE.
include(CheckCXXSourceCompiles)
include(CheckLibraryExists)
# 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<long long> x;
int main() {
return std::atomic_is_lock_free(&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);
return std::atomic_is_lock_free(&x);
}
"
${varname})
set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
endfunction(check_working_cxx_atomics64)
function(check_working_cxx_atomics_2args varname)
set(OLD_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
check_cxx_source_compiles(
"
int main() {
__atomic_load(nullptr, 0);
return 0;
}
"
${varname})
set(CMAKE_REQUIRED_LIBRARIES ${OLD_CMAKE_REQUIRED_LIBRARIES})
endfunction(check_working_cxx_atomics_2args)
function(check_working_cxx_atomics64_2args varname)
set(OLD_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
check_cxx_source_compiles(
"
int main() {
__atomic_load_8(nullptr, 0);
return 0;
}
"
${varname})
set(CMAKE_REQUIRED_LIBRARIES ${OLD_CMAKE_REQUIRED_LIBRARIES})
endfunction(check_working_cxx_atomics64_2args)
# First check if atomics work without the library.
check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB)
set(ATOMIC_LIBRARY "")
# 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(NOT HAVE_LIBATOMIC)
check_working_cxx_atomics_2args(HAVE_LIBATOMIC_2ARGS)
endif()
if(HAVE_LIBATOMIC OR HAVE_LIBATOMIC_2ARGS)
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
set(ATOMIC_LIBRARY "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()
# 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(NOT HAVE_CXX_LIBATOMICS64)
check_working_cxx_atomics64_2args(HAVE_CXX_LIBATOMICS64_2ARGS)
endif()
if(HAVE_CXX_LIBATOMICS64 OR HAVE_CXX_LIBATOMICS64_2ARGS)
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
set(ATOMIC_LIBRARY "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()
endif()
endif()
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