[PATCH] D156777: [SelectionDAG] Add/Improve cases in `isKnownNeverZero`

[Noah Goldstein via Phabricator via llvm-commits]

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1. Handle casts a bit more cleanly just with a loop rather than with recursion.

2. Add additional cases for smin/smax

3 ) For shifts we can also deduce non-zero if the maximum shift amount

  on the known 1s is non-zero.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156777

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/test/CodeGen/X86/known-never-zero.ll

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