[llvm] [InstCombine] Fold adds + shifts with nuw flags (PR #88193)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

This looks fine, but can you please clean up the alive2 proofs in the PR description? They seem to contain a whole bunch of stuff that is not related to the fold implemented here, like things with ashr and muls.

The proofs should all have the base shl+add+lshr sequence, just with different flags.

https://github.com/llvm/llvm-project/pull/88193