[llvm] [RISCV][VLOPT] Add support for checkUsers when UserMI is a Single-Width Integer Reduction (PR #120345)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> I think the net effect of this change is to simply treat the scalar value as consuming VL elements. This is a conservative approximation (i.e. correct). However, can't the same effect be achieved by having getOperandInfo return that result for the scalar operand, and then removing the special case entirely?
> 
> Your code as written is missing the check that the scalar operand has the same SEW as the instruction defining that value. That's a functional bug.

I made this less conservative and took your advice just to make the VL=1.

https://github.com/llvm/llvm-project/pull/120345