[PATCH] D22630: Loop rotation

Aditya Kumar via llvm-commits llvm-commits at lists.llvm.org
Tue Oct 18 12:14:38 PDT 2016

hiraditya added a comment.

In https://reviews.llvm.org/D22630#568508, @mzolotukhin wrote:

> > I have updated the loop rotation to add a metadata if the loop rotation was successful, such that it does not rotate the loop multiple times.
> Can we do it without metadata? Why can't we tell if a loop need to be rotated just by examining it (and after it is rotated, subsequent examination should tell that no rotation is need, so subsequent invocations of LoopRotate would have no effect)?

For several loops, after rotation, the header will be non-exiting which is checked already. But that is not true for all rotated loops.
Is there a way to find out if an instruction/basic-block was alrady in the loop earlier.


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