[PATCH] D79041: [InstCombine] Fold or(zext(bswap(x)),shl(zext(bswap(y)),bw/2)) -> bswap(or(zext(x),shl(zext(y), bw/2))

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: spatel, lebedev.ri, nikic.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

This adds a general combine that can be used to fold:

  or(zext(OP(x)), shl(zext(OP(y)),bw/2))
  -->
  OP(or(zext(x), shl(zext(y),bw/2)))

Allowing us to widen 'concat-able' style or+zext patterns - I've just set this up for BSWAP but we could use this for other similar ops (BITREVERSE for instance).

We already do something similar for binop(bswap(x),bswap(y)) --> bswap(binop(x,y))

Fixes PR45715


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79041

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/test/Transforms/InstCombine/or-concat.ll

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