[all-commits] [llvm/llvm-project] 114d74: [VPlan] Expand VPBlendRecipes to select instructio...

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 114d74e39151ea60afd211a307011f3943ecc9a9
      https://github.com/llvm/llvm-project/commit/114d74e39151ea60afd211a307011f3943ecc9a9
  Author: Luke Lau <luke at igalia.com>
  Date:   2025-07-23 (Wed, 23 Jul 2025)

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

  Log Message:
  -----------
  [VPlan] Expand VPBlendRecipes to select instructions. NFC (#133993)

When looking at some EVL tail folded code in SPEC CPU 2017 I noticed we
sometimes have both VPBlendRecipes and select VPInstructions in the same
plan:

    EMIT vp<%active.lane.mask> = active lane mask vp<%5>, vp<%3>
    EMIT vp<%7> = icmp ...
    EMIT vp<%8> = logical-and vp<%active.lane.mask>, vp<%7>
    BLEND ir<%8> = ir<%n.015> ir<%foo>/vp<%8>
    EMIT vp<%9> = select vp<%active.lane.mask>, ir<%8>, ir<%n.015>

Since a blend will ultimately generate a chain of selects, we could fold
the blend into the select:

    EMIT vp<%active.lane.mask> = active lane mask vp<%5>, vp<%3>
    EMIT vp<%7> = icmp ...
    EMIT vp<%8> = logical-and vp<%active.lane.mask>, vp<%7>
    EMIT ir<%8> = select vp<%8>, ir<%foo>, ir<%n.015>

So as a first step, this patch expands blends to a series of select
instructions, which may allow them to be simplified further with other
select instructions.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications