[PATCH] D91481: [LoopUnroll] Discount uniform instructions in cost models

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

> The reasoning here is that such an expression (as determined by SCEV) will be CSEd once the loop is unrolled.

Is that really the case? I don't think unrolling itself does any CSE, and runtime unrolling is run at the very end of the pipeline, so we don't have any EarlyCSE or GVN passes after it.

Also, the converse question: Why have invariant instructions not been hoisted by LICM before unrolling is reached?


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https://reviews.llvm.org/D91481