[all-commits] [llvm/llvm-project] 8f2466: Reapply "[VPlan] Compute cost of more replicating ...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8f2466bc72a5ab163621cb1bf4bf53a27f1cefe7
      https://github.com/llvm/llvm-project/commit/8f2466bc72a5ab163621cb1bf4bf53a27f1cefe7
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2025-10-02 (Thu, 02 Oct 2025)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/lib/Transforms/Vectorize/VPlan.cpp
    M llvm/lib/Transforms/Vectorize/VPlanHelpers.h
    M llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

  Log Message:
  -----------
  Reapply "[VPlan] Compute cost of more replicating loads/stores in ::computeCost. (#160053)" (#161724)

This reverts commit f61be4352592639a0903e67a9b5d3ec664ad4d23.

Recommit a small fix handling scalarization overhead consistently with
legacy cost model if a load is used directly as operand of another
memory operation, which fixes
https://github.com/llvm/llvm-project/issues/161404.

Original message:
Update VPReplicateRecipe::computeCost to compute costs of more
replicating loads/stores.

There are 2 cases that require extra checks to match the legacy cost
model:
1. If the pointer is based on an induction, the legacy cost model passes
its SCEV to getAddressComputationCost. In those cases, still fall back
to the legacy cost. SCEV computations will be added as follow-up
2. If a load is used as part of an address of another load, the legacy
cost model skips the scalarization overhead. Those cases are currently
handled by a usedByLoadOrStore helper.

Note that getScalarizationOverhead also needs updating, because when the
legacy cost model computes the scalarization overhead, scalars have not
been collected yet, so we can't each for replicating recipes to skip
their cost, except other loads. This again can be further improved by
modeling inserts/extracts explicitly and consistently, and compute costs
for those operations directly where needed.

PR: https://github.com/llvm/llvm-project/pull/160053



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