[llvm] [LoopPeel] Implement initial peeling off the last loop iteration. (PR #139551)

Mon May 12 06:58:26 PDT 2025

https://github.com/fhahn created https://github.com/llvm/llvm-project/pull/139551

Generalize countToEliminateCompares to also consider peeling off the last iteration if it eliminates a compare. 

At the moment, codegen for peeling off the last iteration is quite restrictive and callers have to make sure that the exit condition can be adjusted when peeling and that the loop executes at least 2 iterations. 

Both will be relaxed in follow-ups.

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