[all-commits] [llvm/llvm-project] ec62de: [VPlan] Handle FirstActiveLane when unrolling. (#1...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ec62dee70349f6d24cab641343a021b6c2fc679a
      https://github.com/llvm/llvm-project/commit/ec62dee70349f6d24cab641343a021b6c2fc679a
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2025-06-27 (Fri, 27 Jun 2025)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/VPlan.h
    M llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
    M llvm/lib/Transforms/Vectorize/VPlanUnroll.cpp
    M llvm/test/Transforms/LoopVectorize/AArch64/single-early-exit-interleave.ll
    M llvm/test/Transforms/LoopVectorize/single-early-exit-interleave.ll
    M llvm/test/Transforms/LoopVectorize/vector-loop-backedge-elimination-early-exit.ll

  Log Message:
  -----------
  [VPlan] Handle FirstActiveLane when unrolling. (#145394)

Currently FirstActiveLane is not handled correctly during
 unrolling. This is currently causing mis-compiles when
 vectorizing early-exit loops with interleaving forced.

This patch updates handling of FirstActiveLane to be analogous to
computing final reduction results: during unrolling, the created copies
for its original operand are added as additional operands, and
FirstActiveLane will always produce the index of the first active lane
across all unrolled iterations.

Note that some of the generated code is still incorrect, as we also need
to handle ExtractElement with FirstActiveLane operands. I will share
patches for those soon as well.

PR: https://github.com/llvm/llvm-project/pull/145394



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