[all-commits] [llvm/llvm-project] f3dcf1: [flang][OpenMP] Support lowering of metadirective ...

[Chi-Chun, Chen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f3dcf16115f862f6fa5ea8e520b371f7e57a9c3d
      https://github.com/llvm/llvm-project/commit/f3dcf16115f862f6fa5ea8e520b371f7e57a9c3d
  Author: Chi-Chun, Chen <chichun.chen at hpe.com>
  Date:   2026-06-02 (Tue, 02 Jun 2026)

  Changed paths:
    M flang/lib/Lower/OpenMP/OpenMP.cpp
    M flang/lib/Lower/OpenMP/Utils.cpp
    M flang/lib/Lower/OpenMP/Utils.h
    R flang/test/Lower/OpenMP/Todo/begin-metadirective.f90
    A flang/test/Lower/OpenMP/Todo/metadirective-declarative.f90
    A flang/test/Lower/OpenMP/Todo/metadirective-dynamic.f90
    R flang/test/Lower/OpenMP/Todo/metadirective-exec.f90
    A flang/test/Lower/OpenMP/Todo/metadirective-loop.f90
    R flang/test/Lower/OpenMP/Todo/metadirective-spec.f90
    A flang/test/Lower/OpenMP/Todo/metadirective-structured-trait-property.f90
    A flang/test/Lower/OpenMP/Todo/metadirective-target-device.f90
    A flang/test/Lower/OpenMP/metadirective-construct.f90
    A flang/test/Lower/OpenMP/metadirective-device-arch.f90
    A flang/test/Lower/OpenMP/metadirective-device-isa.f90
    A flang/test/Lower/OpenMP/metadirective-device-kind.f90
    A flang/test/Lower/OpenMP/metadirective-implementation.f90
    A flang/test/Lower/OpenMP/metadirective-nothing.f90
    A flang/test/Lower/OpenMP/metadirective-user.f90
    M flang/test/Semantics/OpenMP/metadirective-common.f90

  Log Message:
  -----------
  [flang][OpenMP] Support lowering of metadirective (part 1) (#193664)

Add lowering support for OpenMP metadirective variants that can be
selected statically. Selection is performed during lowering with
`llvm::omp::OMPContext`, and only the selected directive variant is
lowered.

For example:
  ```fortran
  subroutine static_vendor()
    !$omp metadirective &
    !$omp & when(implementation={vendor(llvm)}: barrier) &
    !$omp & otherwise(nothing)
  end subroutine
```

is lowered to a function containing `omp.barrier`, because `vendor(llvm)` is statically applicable when compiling with Flang.

Applicable variants are represented with `llvm::omp::VariantMatchInfo` and ranked using OpenMP context matching and selector scores from the LLVM frontend.

This patch supports both standalone metadirectives and begin/end
metadirectives. For begin/end metadirectives, the variant is selected
before lowering the enclosed region so that the selected directive
correctly wraps the region.

This initial static-resolution PR supports:

  * implementation={vendor(...)}
  * device={kind(...), isa(...), arch(...)}
  * user={condition(<constant-expr>)}
  * construct={parallel, target, teams, for}
  * default, nothing, and otherwise clauses
 
This patch also preserves `score(...)` on constant user conditions so scored conditions participate correctly in variant ranking. When matching nested construct selectors, it includes constructs introduced by an enclosing selected begin/end metadirective.

Dynamic user conditions (#194424), `target_device` selectors, loop-associated directive variants, and complete construct support are deferred to follow-up patches.

This patch is part of the feature work for #188820.

Assisted by GitHub Copilot and GPT-5.4.



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