[llvm] [SimplifyCFG] Avoid branch threading of divergent conditionals (PR #141867)

[Artem Belevich via llvm-commits]

Artem-B wrote:

> I think we need a separate "undo jump threading" optimization pass

Is that an easily solvable problem? I think when we were trying to undo CFG changes that made CFG un-structured, it proved somewhere between hard and "unsolvable in general case". It may be easier to prevent introducing such changes.

Can we let back-end add a pass that will provide optional hints on what should or should not be jump-threaded, and, possibly other relevant metadata? The need to provide back-end specific tweaks in general passes seems to be a recurring issue.



https://github.com/llvm/llvm-project/pull/141867