[llvm-dev] questionabout loop rotation

Florian Hahn via llvm-dev llvm-dev at lists.llvm.org
Wed Mar 25 15:18:12 PDT 2020

> On Mar 25, 2020, at 18:30, Aditya K <hiraditya at msn.com> wrote:
> >  Aditya, I took a look but I was hoping for a simpler example. And something that is more "usual". As Florian mentioned, these branches are on undefs.
> The branches are like that because I reduced the test cases using bug-point.
> > cc: Florian
> > Have you considered using the existing LoopPeeling infrastructure (part of loop unrolling) to do the peeling? It already peels off iterations from the start up to a threshold, if it makes a condition in the loop body invariant. 
> After looking a little bit into the code of loop peeling, it only seems to work on loops with single exits.

Right, but I think that is mostly a limitation of the current cost modeling. For example, recently support got added for peeling loops with multiple de-op exits. I was mostly wondering how it would fit conceptually.

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