[PATCH] D148404: [ValueTracking] Apply the isKnownNonZero techniques in `ashr`/`lshl` to `shl` and vice-versa

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n created this revision.
goldstein.w.n added reviewers: majnemer, spatel, nikic.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
goldstein.w.n requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

For all shifts we can apply the same two optimizations.

1. `ShiftOp(KnownVal.One, Max(KnownCnt)) != 0` -> result is non-zero
2. If already known `Val != 0` and we only shift out zeros (based on `Max(KnownCnt)`) -> result is non-zero

The former exists for `shl` and the latter (for constant `Cnt`) exists
for `ashr`/`lshr`.

This patch improves the latter to use `Max(KnownCnt)` instead of
relying on a constant shift `Cnt` and applies both techniques for all
shift ops.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148404

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Analysis/ValueTracking/known-non-zero.ll
  llvm/test/Transforms/InstCombine/ctpop-pow2.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D148404.513822.patch
Type: text/x-patch
Size: 7405 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230415/ec42fc6f/attachment.bin>