[PATCH] D57156: [x86] narrow a shuffle that doesn't use or set any high elements

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon accepted this revision.
RKSimon added a comment.
This revision is now accepted and ready to land.

LGTM - thanks!

In D57156#1370481 <https://reviews.llvm.org/D57156#1370481>, @spatel wrote:

> Note: Tests with AVX512 and 512-bit vectors are not showing the same improvements as other targets/tests because we don't know how to collapse an (extract (extract V, 0), 0) into 1 extract node yet. I'm imagining that patch is similar to the insert-of-insert that in D56604 <https://reviews.llvm.org/D56604>. Once we have that fold, we'll get several more narrowing of binops like we see here. But like this patch, that one also appears to expose a shuffle lowering hole, so it might need a preliminary patch to avoid a regression.


Please can you raise a bug about this?


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https://reviews.llvm.org/D57156