[llvm] [RISCV] Inhibit DAG folding shl through zext.w pattern with zba (PR #91626)

[Craig Topper via llvm-commits]

topperc wrote:

> In practice, we can't undo this during ISEL resulting in worse code in some cases.

Why can't we undo it? Does it move too far away?

https://github.com/llvm/llvm-project/pull/91626