From 6215c6227e788c7c13d5d83d469e5b0019a0f1af Mon Sep 17 00:00:00 2001
From: Xerxes Ranby <xerxes@zafena.se>
Date: Fri, 17 Jul 2009 19:22:41 +0000
Subject: [PATCH] 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
---
 cmake/config-ix.cmake              |  3 +++
 cmake/modules/CheckAtomic.cmake    | 18 ++++++++++++++++++
 include/llvm/Config/config.h.cmake |  3 +++
 3 files changed, 24 insertions(+)
 create mode 100644 cmake/modules/CheckAtomic.cmake

diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake
index 731071ef85b..5833119e26f 100755
--- a/cmake/config-ix.cmake
+++ b/cmake/config-ix.cmake
@@ -76,6 +76,9 @@ if( LLVM_USING_GLIBC )
   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 00000000000..27bbaba6998
--- /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()
diff --git a/include/llvm/Config/config.h.cmake b/include/llvm/Config/config.h.cmake
index 051114053da..8a52f92503b 100644
--- a/include/llvm/Config/config.h.cmake
+++ b/include/llvm/Config/config.h.cmake
@@ -467,6 +467,9 @@
 /* Installation directory for man pages */
 #undef LLVM_MANDIR
 
+/* Build multithreading support into LLVM */
+#cmakedefine LLVM_MULTITHREADED ${LLVM_MULTITHREADED}
+
 /* Define if this is Unixish platform */
 #cmakedefine LLVM_ON_UNIX ${LLVM_ON_UNIX}