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

[Luke Lau via llvm-commits]

lukel97 wrote:

> Appreciate the effort! Just wondering - for EVL transform, do you expect to generate vp intrinsics during the backedge recipe execution, or will a separate transformation be needed to convert the backedge recipes into WidenIntrinsicRecipes?

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?

Although I just want to double check, I was thinking that doing the regular widening for now would still be correct. Can we convert it to VP intrinsics as a separate task after the EVL transform or is it needed for correctness?

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

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