llvm-project

d9286272 - [VPlan] Cost truncated widened inductions via ::computeCost. (#212786)

[VPlan] Cost truncated widened inductions via ::computeCost. (#212786) Follow-up to https://github.com/llvm/llvm-project/pull/202232 to also compute costs for truncated inductions in ::computeCost, removing the fallback to the legacy cost model unless the loop is fully unrolled. Note that this changes vectorization decisions in both direction, e.g. * now vectorized `@tail_predicate_without_optsize`: legacy costs <16 x i64>, whereas we generate a narrow IV <16 x i8>, which is much cheaper * no longer vectorized `@second_lshr_operand_zero_via_scev()`: we generate 2 IVs (one truncated and one not truncated), which is more expensive than the single IV LV assumes (note that previously we would ignore the cost of the trunc in the cost computation, because the trunc was replaced by the wide truncated IV, which was assumed free. Both cases are due to more accurate cost computations. PR: https://github.com/llvm/llvm-project/pull/212786