cmake: update CheckAtomic

cmake/CheckAtomic.cmake

-# University of Illinois/NCSA
-# Open Source License
-#
-# Copyright (c) 2003-2017 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.
+# atomic builtins are required for threading support.
 
-include(CheckCXXSourceCompiles)
-include(CheckLibraryExists)
+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})
-  get_directory_property(compile_options COMPILE_OPTIONS)
-  set(CMAKE_REQUIRED_FLAGS ${compile_options})
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
   CHECK_CXX_SOURCE_COMPILES("
 #include <atomic>
-#include <cstdint>
-std::atomic<int64_t> v1;
-std::atomic<int64_t> v2;
-int main(int, char**) {
-  return v1 + v2;
-}" ${varname})
+std::atomic<int> x;
+int main() {
+  return 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 0;
+}
+" ${varname})
+  set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
+endfunction(check_working_cxx_atomics64)
 
-if(NOT DEFINED PROXYGEN_COMPILER_IS_GCC_COMPATIBLE)
-  if(CMAKE_COMPILER_IS_GNUCXX)
-    set(PROXYGEN_COMPILER_IS_GCC_COMPATIBLE ON)
-  elseif(MSVC)
-    set(PROXYGEN_COMPILER_IS_GCC_COMPATIBLE OFF)
-  elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
-    set(PROXYGEN_COMPILER_IS_GCC_COMPATIBLE ON)
-  elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "Intel")
-    set(PROXYGEN_COMPILER_IS_GCC_COMPATIBLE ON)
-  endif()
-endif()
 
 # This isn't necessary on MSVC, so avoid command-line switch annoyance
 # by only running on GCC-like hosts.
-if(PROXYGEN_COMPILER_IS_GCC_COMPATIBLE)
+if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
   # First check if atomics work without the library.
   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)
     check_library_exists(atomic __atomic_fetch_add_4 "" HAVE_LIBATOMIC)
-    if(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()
-      list(APPEND CMAKE_CXX_STANDARD_LIBRARIES -latomic)
     else()
       message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
     endif()
   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 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()
+
+## 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.
+CHECK_CXX_SOURCE_COMPILES("
+#ifdef _MSC_VER
+#include <windows.h>
+#endif
+int main() {
+#ifdef _MSC_VER
+        volatile LONG val = 1;
+        MemoryBarrier();
+        InterlockedCompareExchange(&val, 0, 1);
+        InterlockedIncrement(&val);
+        InterlockedDecrement(&val);
+#else
+        volatile unsigned long val = 1;
+        __sync_synchronize();
+        __sync_val_compare_and_swap(&val, 1, 0);
+        __sync_add_and_fetch(&val, 1);
+        __sync_sub_and_fetch(&val, 1);
+#endif
+        return 0;
+      }
+" LLVM_HAS_ATOMICS)
+
+if( NOT LLVM_HAS_ATOMICS )
+  message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
+endif()
\ No newline at end of file