[all-commits] [llvm/llvm-project] 40304d: Reapply "[VPlan] Remove manual region removal when...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 40304d8fefc8872dc8dd2c53f67c7303e40ea727
      https://github.com/llvm/llvm-project/commit/40304d8fefc8872dc8dd2c53f67c7303e40ea727
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2026-03-26 (Thu, 26 Mar 2026)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
    M llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
    M llvm/lib/Transforms/Vectorize/VPlanTransforms.h
    M llvm/test/Transforms/LoopVectorize/AArch64/clamped-trip-count.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/force-target-instruction-cost.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/low_trip_count_predicates.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/optsize_minsize.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/partial-reduce-replicate-extends.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/replicating-load-store-costs-apple.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/replicating-load-store-costs.ll
    M llvm/test/Transforms/LoopVectorize/RISCV/low-trip-count.ll
    M llvm/test/Transforms/LoopVectorize/RISCV/vector-loop-backedge-elimination-with-evl.ll
    M llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
    M llvm/test/Transforms/LoopVectorize/X86/epilog-vectorization-ordered-reduction.ll
    M llvm/test/Transforms/LoopVectorize/X86/load-deref-pred.ll
    M llvm/test/Transforms/LoopVectorize/epilog-vectorization-reductions.ll
    M llvm/test/Transforms/LoopVectorize/find-last.ll
    M llvm/test/Transforms/LoopVectorize/iv-select-cmp-decreasing.ll
    M llvm/test/Transforms/LoopVectorize/load-deref-pred-poison-ub-ops-feeding-pointer.ll
    M llvm/test/Transforms/LoopVectorize/predicated-multiple-exits.ll
    M llvm/test/Transforms/LoopVectorize/reduction-minmax-users-and-predicated.ll
    M llvm/test/Transforms/LoopVectorize/single-early-exit-cond-poison.ll
    M llvm/test/Transforms/LoopVectorize/vector-loop-backedge-elimination-early-exit.ll
    M llvm/test/Transforms/LoopVectorize/vector-loop-backedge-elimination.ll
    M llvm/test/Transforms/PhaseOrdering/ARM/arm_var_q31.ll

  Log Message:
  -----------
  Reapply "[VPlan] Remove manual region removal when simplifying for VF and UF. (#181252)" (#188589)

This reverts commit e30f9c19464bcf1bf1e9f69b63884fb78ad2d05d.

Re-land, now that the reported crash causing the revert has been fixed
as part of 77fb84889 (#187504).

Original message:

Replace manual region dissolution code in
simplifyBranchConditionForVFAndUF with using general
removeBranchOnConst. simplifyBranchConditionForVFAndUF now just creates
a (BranchOnCond true) or updates BranchOnTwoConds.

The loop then gets automatically removed by running removeBranchOnConst.

This removes a bunch of special logic to handle header phi replacements
and CFG updates. With the new code, there's no restriction on what kind
of header phi recipes the loop contains.

Note that VPEVLBasedIVRecipe needs to be marked as readnone. This is
technically unrelated, but I could not find an independent test that
would be impacted.

The code to deal with epilogue resume values now needs updating, because
we may simplify a reduction directly to the start value.

PR: https://github.com/llvm/llvm-project/pull/181252



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