[PATCH] D68789: [LoopNest]: Analysis to discover properties of a loop nest.

[Michael Kruse via Phabricator via llvm-commits]

Meinersbur added a comment.

In D68789#1723852 <https://reviews.llvm.org/D68789#1723852>, @reames wrote:

> First, restricting transformations to perfectly nested loops when there are known techniques to handle imperfect loop nests does not seem worthwhile.  As such, I strongly reject the notion that we should make perfect nesting a requirement for all of our loop transformations.


I'd see it as a tool for transformations that need perfect loop nests (interchange, tiling, unrollandjam, ...) rather as a new requirement.

> Secondly, even if I accept the premise that perfect nesting is useful, I do not see the value of this analysis pass.  We have an existing description of a loop and loop nest in loop info.  How is this anything more than a set of helper function implemented over the existing analysis?  (i.e. LoopNestUtils.hpp/cpp?)

We already had this discussion in D63459 <https://reviews.llvm.org/D63459>. In this case, I don't have a strong opinion on whether it should be a LoopAnalysis or a utility. In this case an advantage could be that passes may mark the analysis as preserved (e.g. it doesn't change the loop nest) rather it being recomputed.


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