llvm-project

730a07f2 - [LV] Only create partial reductions when profitable. (#181706)

[LV] Only create partial reductions when profitable. (#181706) We want the LV cost-model to make the best possible decision of VF and whether or not to use partial reductions. At the moment, when the LV can use partial reductions for a given VF range, it assumes those are always preferred. After transforming the plan to use partial reductions, it then chooses the most profitable VF. It is possible for a different VF to have been more profitable, if it wouldn't have chosen to use partial reductions. This PR changes that, to first decide whether partial reductions are more profitable for a given chain. If not, then it won't do the transform. This causes some regressions for AArch64 which are addressed in a follow-up PR to keep this one simple.