[PATCH] D110170: [InstCombine] fold cast between shift and mask

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
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and (trunc (lshr X, ShiftC)), C --> and (lshr (trunc X), ShiftC), C

Narrowing the shift should be better for analysis and can lead to follow-on transforms as shown.

Attempt at the general proof in Alive2:
https://alive2.llvm.org/ce/z/tRnnSF

Here are a couple of the specific tests:
https://alive2.llvm.org/ce/z/bCnTp-


https://reviews.llvm.org/D110170

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/test/Transforms/InstCombine/and-narrow.ll

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