spirv-fuzz features transformations that should be applicable by
construction. Assertions are used to detect when such transformations
turn out to be inapplicable. Failures of such assertions indicate bugs
in the fuzzer. However, when using the fuzzer at scale (e.g. in
ClusterFuzz) reports of these assertion failures create noise, and
cause the fuzzer to exit early. This change adds an option whereby
inapplicable transformations can be ignored. This reduces noise and
allows fuzzing to continue even when a transformation that should be
applicable but is not has been erroneously created.
This PR introduces FuzzerPassAddLoopPreheaders, which:
- Finds existing loop headers
- If they have no simple preheader (where simple means that the
preheader itself is not a loop header), randomly decides whether
to add one.
Fixes#3621.
