[PATCH] D53037: [InstCombine] combine a shuffle and an extract subvector shuffle

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

That case is specifically interesting because when it's split, each half is lowered to a different shuffle, and both shuffles are expensive.

Obviously you could try to find that specific pattern in SelectionDAG on AArch64, but I'm not sure it makes sense to expect the backend to try; instcombine probably shouldn't be creating difficult-to-solve optimization puzzles.


Repository:
  rL LLVM

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  https://reviews.llvm.org/D53037/new/

https://reviews.llvm.org/D53037