[PATCH] D54869: [InstCombine] Determine demanded and known bits for funnel shifts

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

I've added two tests for vectors. It works for the constant splat case, and fails if it's only constant modulo the bitwidth. That may be something we want to handle in the future (also for the zero shift case).

I've opened a bug report for the multi-use case here: https://bugs.llvm.org/show_bug.cgi?id=39771

I think the next step here would be to add support for funnel shifts to DemandedBits analysis and ValueTracking. It won't solve the motivating case either, but may help for other things.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D54869/new/

https://reviews.llvm.org/D54869