[llvm] [VPlan] Introduce VPScalarPHIRecipe, use for can & EVL IV codegen (NFC). (PR #114305)

[Nico Weber via llvm-commits]

nico wrote:

It looks like the post-commit feedback commit make clang crash quite a bit: http://45.33.8.238/linux/154891/step_6.txt

Please take a look.

https://github.com/llvm/llvm-project/pull/114305