[llvm] [VPlan] Expand VPWidenIntOrFpInductionRecipe into separate recipes (PR #118638)

[Mel Chen via llvm-commits]

Mel-Chen wrote:

> I'm trying to get rid of the backedge recipe and just replace it with regular VPInstructions + VPWidenRecipes. In that case we could then rerun transformRecipestoEVLRecipes after the expansion?

Yes, VPInstructions should be good enough for correctness. Transform mul/ add to vp.mul/ vp.add is for performance.
> 
> As a side note on RISC-V, I wonder if RISCVLOptimizer.cpp from #108640 might take care of removing the VL toggle for us in the backend as well

I have the same thought, but it doesn't seem to be accepted.
https://github.com/llvm/llvm-project/pull/109614#issuecomment-2396841914

https://github.com/llvm/llvm-project/pull/118638