[PATCH] D147968: [TTI][BPF]: Undo specific transform-preventing passes and add TTI hooks

[Nikita Popov via Phabricator via llvm-commits]

nikic requested changes to this revision.
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This has already been discussed in D147078 <https://reviews.llvm.org/D147078>. All the middle-end maintainers who chimed in on that one were opposed to the proposal, and I don't think their responses will be different this time. I don't really want to repeat that discussion one more time here, because it felt a bit like talking at a wall. If you want to pursue this further, I would suggest starting an RFC on Discourse, because it seems pretty clear that we don't have a consensus between BPF and middle-end maintainers here.

PS: I would recommend shifting your thinking about these undo transforms from "precisely undo what this pass did" to "legalize IR for BPF". The draft patch at D147990 <https://reviews.llvm.org/D147990> is needlessly complex because it tries to precisely undo what LICM does (down to loop invariance checks!) instead of treating it as a generic legalization problem.


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  https://reviews.llvm.org/D147968/new/

https://reviews.llvm.org/D147968