Asyncify: whitelist and blacklist support (#2264)

The blacklist means "functions here are to be ignored and not instrumented, we can assume they never unwind." The whitelist means "only these functions, and no others, can unwind." I had hoped such lists would not be necessary, since Asyncify's overhead is much smaller than the old Asyncify and Emterpreter, but as projects have noticed, the overhead to size and speed is still significant. The lists give power users a way to reduce any unnecessary overhead.

A slightly tricky thing is escaping of names: we escape names from the names section (see #2261 #1646). The lists arrive in human-readable format, so we escape them before comparing to the internal escaped names. To enable that I refactored wasm-binary a little bit to provide the escaping logic, cc @yurydelendik

If both lists are specified, an error is shown (since that is meaningless). If a name appears in a list that is not in the module, we show a warning, which will hopefully help people debug typos etc. I had hoped to make this an error, but the problem is that due to inlining etc. a single list will not always work for both unoptimized and optimized builds (a function may vanish when optimizing, due to duplicate function elimination or inlining).

Fixes #2218.

1 files changed, 21 insertions, 0 deletions

diff --git a/test/unit/test_asyncify.py b/test/unit/test_asyncify.py
index 479d24cab..40ee160d2 100644
--- a/test/unit/test_asyncify.py
+++ b/test/unit/test_asyncify.py
@@ -1,4 +1,5 @@
 import os
+import subprocess
 
 from scripts.test.shared import WASM_OPT, WASM_DIS, WASM_SHELL, NODEJS, run_process
 from utils import BinaryenTestCase
@@ -27,3 +28,23 @@ class AsyncifyTest(BinaryenTestCase):
     output = run_process(WASM_SHELL + ['a.wast'], capture_output=True).stdout
     with open(self.input_path('asyncify-pure.txt')) as f:
       self.assertEqual(f.read(), output)
+
+  def test_asyncify_list_bad(self):
+    for arg, warning in [
+      ('--pass-arg=asyncify-blacklist@nonexistent', 'nonexistent'),
+      ('--pass-arg=asyncify-whitelist@nonexistent', 'nonexistent'),
+      ('--pass-arg=asyncify-blacklist@main', None),
+      ('--pass-arg=asyncify-whitelist@main', None),
+    ]:
+      print(arg, warning)
+      err = run_process(WASM_OPT + [self.input_path('asyncify-pure.wast'), '--asyncify', arg], stdout=subprocess.PIPE, stderr=subprocess.PIPE).stderr.strip()
+      if warning:
+        self.assertIn('warning', err)
+        self.assertIn(warning, err)
+      else:
+        self.assertNotIn('warning', err)
+
+  def test_asyncify_blacklist_and_whitelist(self):
+    proc = run_process(WASM_OPT + [self.input_path('asyncify-pure.wast'), '--asyncify', '--pass-arg=asyncify-whitelist@main', '--pass-arg=asyncify-blacklist@main'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT, check=False)
+    self.assertNotEqual(proc.returncode, 0, 'must error on using both lists at once')
+    self.assertIn('It makes no sense to use both a blacklist and a whitelist with asyncify', proc.stdout)