[llvm-branch-commits] [llvm] release/22.x: [Hexagon] Fix AP register use-before-def and add MIR serialization for liveness tracking (#191010) (PR #192036)

[Brian Cain via llvm-branch-commits]

androm3da wrote:

> this feels like it goes beyond critical bug fixes to be honest

IMO this bugfix is my highest-ranked one for 22.x Hexagon codegen, I've been anxiously awaiting its landing on `main`.  Other cherry-picks could arguably be sub-critical but not this one.

What about this PR seems like it's beyond a critical bugfix?

> are you confident this has had enough testing?

This is a fair question.  After this landed, we don't see any regression on `main` with the `llvm-test-suite` configs I tested.  But I haven't yet tried to build the project that revealed this codegen error (libeigen), to confirm it's effective.

Since I am looking forward to this change landing on 22.x, I'm willing to do any additional testing desired.  Also @pkarveti let me know if you have any ideas for cases that could evoke weaknesses in this change.

https://github.com/llvm/llvm-project/pull/192036