Add support for LLVM's thinLTO

This uses a separate option, b_lto_mode. It works in conjunction with
b_lto_threads.

Fixes #7493

1 files changed, 25 insertions, 0 deletions

diff --git a/run_unittests.py b/run_unittests.py
index aff94c4..2b8812a 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -2864,6 +2864,31 @@ class AllPlatformTests(BasePlatformTests):
                 for e in expected:
                     self.assertIn(e, s['parameters'])
 
+    @skip_if_not_base_option('b_lto_mode')
+    @skip_if_not_base_option('b_lto_threads')
+    def test_lto_mode(self):
+        testdir = os.path.join(self.common_test_dir, '6 linkshared')
+
+        env = get_fake_env(testdir, self.builddir, self.prefix)
+        cc = env.detect_c_compiler(MachineChoice.HOST)
+        if cc.get_id() != 'clang':
+            raise unittest.SkipTest('Only clang currently supports thinLTO')
+        if cc.linker.id not in {'ld.lld', 'ld.gold', 'ld64', 'lld-link'}:
+            raise unittest.SkipTest('thinLTO requires ld.lld, ld.gold, ld64, or lld-link')
+        elif is_windows():
+            raise unittest.SkipTest('LTO not (yet) supported by windows clang')
+
+        self.init(testdir, extra_args=['-Db_lto=true', '-Db_lto_mode=thin', '-Db_lto_threads=8'])
+        self.build()
+        self.run_tests()
+
+        expected = set(cc.get_lto_compile_args(threads=8, mode='thin'))
+        targets = self.introspect('--targets')
+        # This assumes all of the targets support lto
+        for t in targets:
+            for s in t['target_sources']:
+                assert expected.issubset(set(s['parameters'])), f'Incorrect values for {t["name"]}'
+
     def test_dist_git(self):
         if not shutil.which('git'):
             raise unittest.SkipTest('Git not found')