[llvm] [RISCV] Prefer VLS over VLA if costs are equal (PR #100564)

[Philip Reames via llvm-commits]

preames wrote:

> > Worth noting is that adding -mrvv-vector-bits=zvl to both sides results in exactly the same code, and that code appears reasonable.
> 
> I think it is because we are using fixed-vectors with `-mrvv-vector-bits=zvl`.

On the compiler example you posted, we still use scalable types.  We just know the exact size of the scalable type. 

https://github.com/llvm/llvm-project/pull/100564