Introduce a cmake module to figure out whether we need to link with libatomic.

Summary:
This fixes the tests under std/atomics for 32-bit MIPS CPUs where the
8-byte atomic operations call into the libatomic library.

Reviewers: dsanders, mclow.lists, EricWF, jroelofs, joerg

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D16613

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@260235 91177308-0d34-0410-b5e6-96231b3b80d8

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.

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

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")