Re-commit "Introduce a cmake module to figure out whether we need to link with libatomic."

This re-applies commit r260235. However, this time we add -gcc-toolchain
to the compiler's flags when the user has specified the LIBCXX_GCC_TOOLCHAIN
variable.

llvm-svn: 260515

3 files changed, 5 insertions, 0 deletions

diff --git a/libcxx/test/CMakeLists.txt b/libcxx/test/CMakeLists.txt
index b67b3b43f83..88145534f7d 100644
--- a/libcxx/test/CMakeLists.txt
+++ b/libcxx/test/CMakeLists.txt
@@ -15,6 +15,7 @@ pythonize_bool(LIBCXX_ENABLE_SHARED)
 pythonize_bool(LIBCXX_BUILD_32_BITS)
 pythonize_bool(LIBCXX_GENERATE_COVERAGE)
 pythonize_bool(LIBCXXABI_USE_LLVM_UNWINDER)
+pythonize_bool(LIBCXX_HAS_ATOMIC_LIB)
 
 # The tests shouldn't link to any ABI library when it has been linked into
 # libc++ statically or via a linker script.
diff --git a/libcxx/test/libcxx/test/target_info.py b/libcxx/test/libcxx/test/target_info.py
index 7ca08bea193..dc37f7108d3 100644
--- a/libcxx/test/libcxx/test/target_info.py
+++ b/libcxx/test/libcxx/test/target_info.py
@@ -172,6 +172,9 @@ class LinuxLocalTI(DefaultTargetInfo):
             flags += ['-lunwind', '-ldl']
         else:
             flags += ['-lgcc_s', '-lgcc']
+        use_libatomic = self.full_config.get_lit_bool('use_libatomic', False)
+        if use_libatomic:
+            flags += ['-latomic']
         san = self.full_config.get_lit_conf('use_sanitizer', '').strip()
         if san:
             # The libraries and their order are taken from the
diff --git a/libcxx/test/lit.site.cfg.in b/libcxx/test/lit.site.cfg.in
index fa25834d111..9eb2b20a7dc 100644
--- a/libcxx/test/lit.site.cfg.in
+++ b/libcxx/test/lit.site.cfg.in
@@ -20,6 +20,7 @@ config.generate_coverage        = "@LIBCXX_GENERATE_COVERAGE@"
 config.target_info              = "@LIBCXX_TARGET_INFO@"
 config.executor                 = "@LIBCXX_EXECUTOR@"
 config.llvm_unwinder            = "@LIBCXXABI_USE_LLVM_UNWINDER@"
+config.use_libatomic            = "@LIBCXX_HAS_ATOMIC_LIB@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@LIBCXX_SOURCE_DIR@/test/lit.cfg")