[llvm] [LV] Optimize VPWidenIntOrFpInductionRecipe for known TC (PR #118828)

[Hari Limaye via llvm-commits]

hazzlim wrote:

> One more thing I am wondering if we could end up introducing illegal vector types for a target and if we have to check the new type is legal?

I think that it should be fine, given that if the larger type was legal a smaller type with a power-of-2 size should be as well because it can always be promoted to a larger type if necessary. It's not obvious that we check the legality of using a vector of i64 (the default) as the induction variable in the first place?

https://github.com/llvm/llvm-project/pull/118828