[OPENMP] Fix PR38026: Link -latomic when -fopenmp is used.

On Linux atomic constructs in OpenMP require libatomic library. Patch
links libatomic when -fopenmp is used.

llvm-svn: 336467

1 files changed, 5 insertions, 1 deletions

diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 1ecf127c4b9..ee3096813ed 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -479,6 +479,7 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
       bool WantPthread = Args.hasArg(options::OPT_pthread) ||
                          Args.hasArg(options::OPT_pthreads);
+      bool WantAtomic = false;
 
       // FIXME: Only pass GompNeedsRT = true for platforms with libgomp that
       // require librt. Most modern Linux platforms do, but some may not.
@@ -487,13 +488,16 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
                            /* GompNeedsRT= */ true))
         // OpenMP runtimes implies pthreads when using the GNU toolchain.
         // FIXME: Does this really make sense for all GNU toolchains?
-        WantPthread = true;
+        WantAtomic = WantPthread = true;
 
       AddRunTimeLibs(ToolChain, D, CmdArgs, Args);
 
       if (WantPthread && !isAndroid)
         CmdArgs.push_back("-lpthread");
 
+      if (WantAtomic)
+        CmdArgs.push_back("-latomic");
+
       if (Args.hasArg(options::OPT_fsplit_stack))
         CmdArgs.push_back("--wrap=pthread_create");