[llvm] [InstCombine] Funnel shift with negative amount folds to funnel shift in opposite direction (#138334) (PR #138763)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

This is only correct for power of two bit widths, see https://alive2.llvm.org/ce/z/tJ7PAZ

https://github.com/llvm/llvm-project/pull/138763