[llvm] [VPlan] Impl VPlan-based pattern match for ExtendedRed and MulAccRed (NFCI) (PR #113903)

[David Green via llvm-commits]

davemgreen wrote:

The Arm tests still look OK to me, it looks like this could do with a rebase/test fix.

https://github.com/llvm/llvm-project/pull/113903