[PATCH] D38006: [InstCombine] remove extract-of-select vector transform

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a reviewer: nadav.
efriedma added a subscriber: nadav.
efriedma added a comment.

>From https://reviews.llvm.org/D1539:

In https://reviews.llvm.org/D1539#19310, @nadav wrote:

> > When the elements are extracted from a select, do the select on the extracted scalars from the input.
>
> I am not sure that this is always profitable or that it should be done in InstCombine. It is hard to know at IR-level (during inst-combine) if it is better to extract twice and perform a single select or if it is better to perform an vector select and extract once. I think that this kind of decision should be made in SelectionDAG.



https://reviews.llvm.org/D38006