Nikita Popov
6409c21857
It's common to delete some instructions after using SCEVExpander, while it is still live (but will not be used afterwards). In that case, the AssertingVH may trigger. Replace it with a PoisoningVH so that we only detect the case where the SCEVExpander actually is used in a problematic fashion after the instruction removal. The alternative would be to add clear() calls to more code paths. Fixes https://github.com/llvm/llvm-project/issues/83404.