[llvm] [LV] Bundle sub reductions into VPExpressionRecipe (PR #147255)

[Sam Tebbs via llvm-commits]

SamTebbs33 wrote:

Thanks for the review @fhahn , I'll have a look at it tomorrow. I've just rebased the patch on top of main after the sub reduction patch was merged. This involved removing the negated expression type since (non-chained) a sub reduction is now represented with a subtraction, rather than an addition with a negated input.

https://github.com/llvm/llvm-project/pull/147255