[PATCH] D132237: [AArch64] expand is-power-of-2 pattern that uses popcount

[Sanjay Patel via Phabricator via llvm-commits]

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(ctpop x) == 1 --> (x != 0) && ((x & x-1) == 0)

This duplicates code in generic target combining. That code doesn't fire for AArch64 because we have custom lowering for CTPOP alone, so the generic expansion assumes the target can do better in that case.

Another potential fix would be to add a TLI hook around the generic combine, but I didn't see any other targets or patterns that would benefit.

This should fix issue #57225 <https://github.com/llvm/llvm-project/issues/57225>


https://reviews.llvm.org/D132237

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/test/CodeGen/AArch64/arm64-popcnt.ll

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