Implement cmake LLVM_MULTITHREADED gcc atomic builtin checks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76221 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake
index 731071e..5833119 100755
--- a/cmake/config-ix.cmake
+++ b/cmake/config-ix.cmake
@@ -76,6 +76,9 @@
add_llvm_definitions( -D_GNU_SOURCE )
endif()
+# Define LLVM_MULTITHREADED if gcc atomic builtins exists.
+include(CheckAtomic)
+
include(CheckCXXCompilerFlag)
check_cxx_compiler_flag("-fPIC" SUPPORTS_FPIC_FLAG)
diff --git a/cmake/modules/CheckAtomic.cmake b/cmake/modules/CheckAtomic.cmake
new file mode 100644
index 0000000..27bbaba
--- /dev/null
+++ b/cmake/modules/CheckAtomic.cmake
@@ -0,0 +1,18 @@
+# atomic builtins are required for threading support.
+
+INCLUDE(CheckCXXSourceCompiles)
+
+CHECK_CXX_SOURCE_COMPILES("
+int main() {
+ 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);
+ return 0;
+ }
+" LLVM_MULTITHREADED)
+
+if( NOT LLVM_MULTITHREADED )
+ message(STATUS "Warning: LLVM will be built thread-unsafe because atomic builtins are missing")
+endif()