Warn when running a pass not compatible with DWARF (#3506)

Previously the addDefault* methods would avoid adding opt passes that we
know are incompatible with DWARF. However, that didn't handle the case of
passes that are added in other ways. For example, when running Asyncify,
emcc will run --flatten before, and that pass is not compatible with DWARF.
This PR lets us warn on that by annotating the passes themselves. Then we
use those annotation to either not run a pass at all (matching the previous
behavior) or to show a warning when necessary.

Fixes emscripten-core/emscripten#13288 . That is, concretely
after this PR running asyncify + DWARF will show a warning to the user.

1 files changed, 12 insertions, 0 deletions

diff --git a/test/unit/test_dwarf.py b/test/unit/test_dwarf.py
index 5078efeeb..37abf6b18 100644
--- a/test/unit/test_dwarf.py
+++ b/test/unit/test_dwarf.py
@@ -1,4 +1,5 @@
 import os
+import subprocess
 
 from scripts.test import shared
 from . import utils
@@ -14,3 +15,14 @@ class DWARFTest(utils.BinaryenTestCase):
             args = [os.path.join(path, name)] + \
                    ['-g', '--dwarfdump', '--roundtrip', '--dwarfdump']
             shared.run_process(shared.WASM_OPT + args, capture_output=True)
+
+    def test_dwarf_incompatibility(self):
+        warning = 'not fully compatible with DWARF'
+        path = self.input_path(os.path.join('dwarf', 'cubescript.wasm'))
+        args = [path, '-g']
+        # flatten warns
+        err = shared.run_process(shared.WASM_OPT + args + ['--flatten'], stderr=subprocess.PIPE).stderr
+        self.assertIn(warning, err)
+        # safe passes do not
+        err = shared.run_process(shared.WASM_OPT + args + ['--metrics'], stderr=subprocess.PIPE).stderr
+        self.assertNotIn(warning, err)