llvm-project

0c91e977 - [VectorCombine] Refine cost model and decision logic in foldSelectShuffle (#146694)

[VectorCombine] Refine cost model and decision logic in foldSelectShuffle (#146694) After PR #136329, shuffle indices may differ, which can cause the existing cost-based logic to miss optimisation opportunities for binop/shuffle sequences. This patch improves the cost model in foldSelectShuffle to more accurately assess costs, recognising when certain duplicate shuffles do not require actual instructions. Additionally, in break-even cases, this change introduces a check for whether the pattern ultimately feeds into a vector reduction, allowing the transform to proceed when it is likely to be profitable overall.