[all-commits] [llvm/llvm-project] 282937: [LV] Use VScaleForTuning to fine-tune the cost per...

[sdesmalen-arm via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2829376bb267f3364c1225ffaac8b1b8b5688ed1
      https://github.com/llvm/llvm-project/commit/2829376bb267f3364c1225ffaac8b1b8b5688ed1
  Author: Sander de Smalen <sander.desmalen at arm.com>
  Date:   2021-11-08 (Mon, 08 Nov 2021)

  Changed paths:
    M llvm/include/llvm/Analysis/TargetTransformInfo.h
    M llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
    M llvm/include/llvm/CodeGen/BasicTTIImpl.h
    M llvm/lib/Analysis/TargetTransformInfo.cpp
    M llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    A llvm/test/Transforms/LoopVectorize/AArch64/scalable-vectorization-cost-tuning.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/scalable-vectorization.ll
    M llvm/test/Transforms/LoopVectorize/AArch64/scalable-vf-hint.ll

  Log Message:
  -----------
  [LV] Use VScaleForTuning to fine-tune the cost per lane.

When targeting a specific CPU with scalable vectorization, the knowledge
of that particular CPU's vscale value can be used to tune the cost-model
and make the cost per lane less pessimistic.

If the target implements 'TTI.getVScaleForTuning()', the cost-per-lane
is calculated as:

  Cost / (VScaleForTuning * VF.KnownMinLanes)

Otherwise, it assumes a value of 1 meaning that the behavior
is unchanged and calculated as:

  Cost / VF.KnownMinLanes

Reviewed By: kmclaughlin, david-arm

Differential Revision: https://reviews.llvm.org/D113209