[llvm] [RISCV][IR] Implement verifier check for llvm.experimental.vp.splice immediate. (PR #147458)

[Craig Topper via llvm-commits]

topperc wrote:

> I think we should relax this in the LangRef. Extractelement and insertelement assert that scalable vectors fit within the runtime length, i.e between the minimum and the maximum:

Is it useful to have a vector.splice or vp.splice that would be out of bounds when vscale is the lowest value in the vscale_range? We could define it to produce poison but that would mean it's poison for some value of vscale and not others.

https://github.com/llvm/llvm-project/pull/147458