[PATCH] D149577: [InstCombine] Improve bswap optimization

[Austin Chang via Phabricator via llvm-commits]

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Fold the following case on IR InstCombine pass and SelectionDAG combiner

  bswap(logic_op(x, bswap(y))) -> logic_op(bswap(x), y)
  bswap(logic_op(bswap(x), y)) -> logic_op(x, bswap(y))
  bswap(bswap(x)) -> x (for duplicated bswap introduced by other optimizations)

For related optimization `logic_op(bswap(x), bswap(y)) -> bswap(logic_op(x, y))`, I also add a change which I believe to align with the same optimization in SelectionDAG on the one-use constraints.

     if (match(OldRHS, m_BSwap(m_Value(NewRHS)))) {
       // OP( BSWAP(x), BSWAP(y) ) -> BSWAP( OP(x, y) )
  -    if (!OldLHS->hasOneUse() && !OldRHS->hasOneUse())
  +    if (!OldLHS->hasOneUse() || !OldRHS->hasOneUse())
         return nullptr;


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149577

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/bswap-fold.ll

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