[PATCH] D73501: [SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668)

Tue Mar 17 00:08:43 PDT 2020

lebedev.ri added a comment.

In D73501#1925618 <https://reviews.llvm.org/D73501#1925618>, @efriedma wrote:

> > The goal of this change in particular was to really try to get rid of
> >  uses of IV outside of the loop, since that was one of the obstacles
> >  preventing vectorization in one of the loops i looked at.
>
> Maybe we should teach the vectorizer to rewrite exit values?  If we know a loop will be vectorized after rewriting exit values, there's a stronger incentive to rewrite them.  Not sure how hard that would be?  Off the top of my head, it should be straightforward to fit into the vectorizer code that classifies instructions.

That might be worth exploring.

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https://reviews.llvm.org/D73501