[PATCH] D115145: [Analysis][AArch64] Add on overhead costs for fixed-width gathers and scatters

[David Sherwood via Phabricator via llvm-commits]

david-arm added a comment.

In D115145#3175745 <https://reviews.llvm.org/D115145#3175745>, @dmgreen wrote:

>> This patches increases the cost of fixed-width gathers and scatters that will end up scalarising anyway.
>
> Do you know if isLegalMaskedGather/Scatter is returning true for these gathers that will jut be scalarized? It can be difficult at times to make isLegalMaskedGather very precise.

Yeah the problem is that currently the vectoriser only passes the element type to isLegalMaskedGather/Scatter and isLegalMaskedLoad/Store. So we have no way to distinguish between fixed-width and scalable except via the cost model. I think we would also like to fix that at some point, but in the short term this simple cost model change helps.


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