Fuzzer: Ignore things we should ignore even if the process succeeded (#3864)

We only ignored known issues if the process failed. However, some things
do not bring the process down, but are still necessary to ignore, which this
fixes.

Another approach might be to make all the things we need to ignore fail
the entire process. However, that could be annoying for other debugging:
we don't want a host limit on say hitting a VM limit on recursion to bring
down the entire process, as those limits manifest as traps, and we can
still run after them (and do need to test that). The specific host limit that
made me fix this was the trap on OOM when trying to allocate an array
of size 4GB.

1 files changed, 22 insertions, 16 deletions

diff --git a/scripts/fuzz_opt.py b/scripts/fuzz_opt.py
index 7580a59a0..5caede369 100755
--- a/scripts/fuzz_opt.py
+++ b/scripts/fuzz_opt.py
@@ -370,25 +370,31 @@ def fix_spec_output(out):
 
 
 def run_vm(cmd):
-    # ignore some types of errors
-    known_issues = [
-        # can be caused by flatten, ssa, etc. passes
-        'local count too large',
-        # https://github.com/WebAssembly/binaryen/issues/3767
-        # note that this text is a little too broad, but the problem is rare
-        # enough that it's unlikely to hide an unrelated issue
-        'found br_if of type',
-        # all host limitations are arbitrary and may differ between VMs and also
-        # be affected by optimizations, so ignore them.
-        HOST_LIMIT_PREFIX,
-    ]
-    try:
-        return run(cmd)
-    except subprocess.CalledProcessError:
-        output = run_unchecked(cmd)
+    def filter_known_issues(output):
+        known_issues = [
+            # can be caused by flatten, ssa, etc. passes
+            'local count too large',
+            # https://github.com/WebAssembly/binaryen/issues/3767
+            # note that this text is a little too broad, but the problem is rare
+            # enough that it's unlikely to hide an unrelated issue
+            'found br_if of type',
+            # all host limitations are arbitrary and may differ between VMs and also
+            # be affected by optimizations, so ignore them.
+            HOST_LIMIT_PREFIX,
+        ]
         for issue in known_issues:
             if issue in output:
                 return IGNORE
+        return output
+
+    try:
+        # some known issues do not cause the entire process to fail
+        return filter_known_issues(run(cmd))
+    except subprocess.CalledProcessError:
+        # other known issues do make it fail, so re-run without checking for
+        # success and see if we should ignore it
+        if filter_known_issues(run_unchecked(cmd)) == IGNORE:
+            return IGNORE
         raise