[PATCH] D31821: Remove redundant copy in recurrences

[Daniel Berlin via llvm-commits]

The normal path to finding recurrences like this would be to follow def-use
chains using an SCC algorithm, and then do something with the members of
the component it comes up with.
I presume you are doing something else because it's difficult to get that
info at this point in the compiler?



On Fri, May 19, 2017 at 1:14 PM, Taewook Oh via Phabricator via
llvm-commits <llvm-commits at lists.llvm.org> wrote:

> twoh added a comment.
>
> @wmi Thank you for your reply. I agree on you that we should consider tied
> operand group, and as @qcolombet mentioned in the previous comment, if tie
> operand information is already available before this pass, I'd like to
> discuss where would be the best place to implement this.
>
> I'm afraid I couldn't understand your second point. In the example there
> is a recurrence cycle of vreg0-->vreg13-->vreg3-->vreg10-->vreg0 as well,
> and what this patch does is commuting (vreg0, vreg1) and (vreg2, vreg10) to
> remove the copy. Did I miss something?
>
>
> https://reviews.llvm.org/D31821
>
>
>
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