[all-commits] [llvm/llvm-project] 911055: [VPlan] Consistently use (Part, 0) for first lane ...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 911055e34f2b1530d9900e23873e300b77ea8d96
      https://github.com/llvm/llvm-project/commit/911055e34f2b1530d9900e23873e300b77ea8d96
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2024-02-26 (Mon, 26 Feb 2024)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/lib/Transforms/Vectorize/VPlan.cpp
    M llvm/lib/Transforms/Vectorize/VPlan.h
    M llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
    M llvm/lib/Transforms/Vectorize/VPlanValue.h
    M llvm/test/Transforms/LoopVectorize/AArch64/tail-folding-styles.ll
    M llvm/test/Transforms/LoopVectorize/X86/small-size.ll

  Log Message:
  -----------
  [VPlan] Consistently use (Part, 0) for first lane scalar values (#80271)

At the moment, some VPInstructions create only a single scalar value,
but use VPTransformatState's 'vector' storage for this value. Those
values are effectively uniform-per-VF (or in some cases
uniform-across-VF-and-UF). Using the vector/per-part storage doesn't
interact well with other recipes, that more accurately using (Part,
Lane) to look up scalar values and prevents VPInstructions creating
scalars from interacting with other recipes working with scalars.

This PR tries to unify handling of scalars by using (Part, 0) for scalar
values where only the first lane is demanded. This allows using
VPInstructions with other recipes like VPScalarCastRecipe and is also
needed when using VPInstructions in more cases otuside the vector loop
region to generate scalars.

Depends on https://github.com/llvm/llvm-project/pull/80269



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