Differential D16184 Diff 49506 cmake/modules/CheckAtomic.cmake

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cmake/modules/CheckAtomic.cmake

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		1		# ==============================================================================
		2		# LLVM Release License
		3		# ==============================================================================
		4		# University of Illinois/NCSA
		5		# Open Source License
		6		#
		7		# Copyright (c) 2003-2018 University of Illinois at Urbana-Champaign.
		8		# All rights reserved.
		9		#
		10		# Developed by:
		11		#
		12		# LLVM Team
		13		#
		14		# University of Illinois at Urbana-Champaign
		15		#
		16		# http://llvm.org
		17		#
		18		# Permission is hereby granted, free of charge, to any person obtaining a copy of
		19		# this software and associated documentation files (the "Software"), to deal with
		20		# the Software without restriction, including without limitation the rights to
		21		# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
		22		# of the Software, and to permit persons to whom the Software is furnished to do
		23		# so, subject to the following conditions:
		24		#
		25		# * Redistributions of source code must retain the above copyright notice,
		26		# this list of conditions and the following disclaimers.
		27		#
		28		# * Redistributions in binary form must reproduce the above copyright notice,
		29		# this list of conditions and the following disclaimers in the
		30		# documentation and/or other materials provided with the distribution.
		31		#
		32		# * Neither the names of the LLVM Team, University of Illinois at
		33		# Urbana-Champaign, nor the names of its contributors may be used to
		34		# endorse or promote products derived from this Software without specific
		35		# prior written permission.
		36		#
		37		# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
		38		# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
		39		# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
		40		# CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
		41		# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
		42		# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
		43		# SOFTWARE.
		44
		45		INCLUDE(CheckCXXSourceCompiles)
		46		INCLUDE(CheckLibraryExists)
		47
		48		# Sometimes linking against libatomic is required for atomic ops, if
		49		# the platform doesn't support lock-free atomics.
		50
		51		function(check_working_cxx_atomics varname)
		52		set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
		53		set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
		54		CHECK_CXX_SOURCE_COMPILES("
		55		#include <atomic>
		56		std::atomic<int> x;
		57		int main() {
		58		return std::atomic_is_lock_free(&x);
		59		}
		60		" ${varname})
		61		set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
		62		endfunction(check_working_cxx_atomics)
		63
		64		function(check_working_cxx_atomics64 varname)
		65		set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
		66		set(CMAKE_REQUIRED_FLAGS "-std=c++11 ${CMAKE_REQUIRED_FLAGS}")
		67		CHECK_CXX_SOURCE_COMPILES("
		68		#include <atomic>
		69		#include <cstdint>
		70		std::atomic<uint64_t> x (0);
		71		int main() {
		72		uint64_t i = x.load(std::memory_order_relaxed);
		73		return std::atomic_is_lock_free(&x);
		74		}
		75		" ${varname})
		76		set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
		77		endfunction(check_working_cxx_atomics64)
		78
		79
		80		# This isn't necessary on MSVC, so avoid command-line switch annoyance
		81		# by only running on GCC-like hosts.
		82		if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
		83		# First check if atomics work without the library.
		84		check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITHOUT_LIB)
		85		# If not, check if the library exists, and atomics work with it.
		86		if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
		87		check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
		88		if( HAVE_LIBATOMIC )
		89		list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
		90		check_working_cxx_atomics(HAVE_CXX_ATOMICS_WITH_LIB)
		91		if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
		92		message(FATAL_ERROR "Host compiler must support std::atomic!")
		93		endif()
		94		else()
		95		message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
		96		endif()
		97		endif()
		98		endif()
		99		# Check for 64 bit atomic operations.
		100		if(MSVC)
		101		set(HAVE_CXX_ATOMICS64_WITHOUT_LIB True)
		102		else()
		103		check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITHOUT_LIB)
		104		endif()
		105
		106		# If not, check if the library exists, and atomics work with it.
		107		if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
		108		check_library_exists(atomic __atomic_load_8 "" HAVE_CXX_LIBATOMICS64)
		109		if(HAVE_CXX_LIBATOMICS64)
		110		list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
		111		check_working_cxx_atomics64(HAVE_CXX_ATOMICS64_WITH_LIB)
		112		if (NOT HAVE_CXX_ATOMICS64_WITH_LIB)
		113		message(FATAL_ERROR "Host compiler must support std::atomic!")
		114		endif()
		115		else()
		116		message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
		117		endif()
		118		endif()