[PATCH] D157755: [InstSimplify] Use knownbits for simplifying `(icmp ugt/ule (or X, Y), X)`; PR64610

[Noah Goldstein via Phabricator via llvm-commits]

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`(icmp ule (or X, Y), X)`

  If there are any unique bits between `X` and `Y`
  --> false

`(icmp ugt (or X, Y), X)`

  If there are any unique bits between `X` and `Y`
  --> true

Proofs: https://alive2.llvm.org/ce/z/igZM4Q

This patch doesn't add any functionality that was previously missing
in LLVM, it just add a bit more to InstructionSimplify.

The rationale is InstCombine can produce `(icmp (or X, Y), X)`
relatively late in the pipeline (after the other passes that would
normally simplify this well have run), leading to missed
optimizations: https://github.com/llvm/llvm-project/issues/64610


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D157755

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/icmp-orx-x.ll

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