[PATCH] D142456: [AArch64][CostModel]: Add costs for zero/sign extend.

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

Yep - I would expect the throughput of most extend operations to be fairly cheap, at least it looks that way from the optimization guides I looked at. They are in line with other instructions, so would usually get a cost of 1.

There is always a chance that getting the cost "wrong" can result in better results. This change will probably make the vectorizer prefer lower vectorization factors or prefer neon over sve. That could result in better results in places, but it is usually better to get the costs more correct. We would need a good justification why they were set 2 x higher.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D142456/new/

https://reviews.llvm.org/D142456