[clang] [llvm] [OptBisect][IR] Adding a new OptPassGate for disabling passes via name (PR #145059)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

> I think this functionality will also help identify passes which drop debug information and help with [the work proposed in this RFC](https://discourse.llvm.org/t/rfc-require-real-or-annotated-source-locations-on-all-instructions/86816).

As it happens, I have been using a downstream modification of opt-bisect as part of my triage process for bugs detected with debugify, by counting optimization passes and printing them alongside detected bugs, making it easy to create reproducers using `--opt-bisect-limit`. This specific change won't be useful for the first pass of the work (detecting missing locations), as Debugify already tracks which pass an error has appeared in.

It would be useful in general for determining passes responsible for dropping debug information, however - I've previously spent time working on finding pass configurations that produce better debug info than the existing O2/O3 pipelines without compromising too greatly on performance - this feature would have made that process easier, and I suspect will make it easier for others to do this in future, so I give a vote for adding this!

https://github.com/llvm/llvm-project/pull/145059