[flang-commits] [flang] [llvm] [flang][OpenMP] Track reachable metadirective replacements (PR #219014)

[via flang-commits]

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@@ -2448,6 +2448,20 @@ static void AppendConstructTraitsForDirective(
     add(llvm::omp::TraitProperty::construct_dispatch_dispatch);
 }
 
+void AppendConstructTraitsForSelector(const parser::OmpTraitSelectorName &name,
+    llvm::omp::VariantMatchInfo &vmi) {
+  if (const auto *dir{std::get_if<llvm::omp::Directive>(&name.u)}) {
+    AppendConstructTraitsForDirective(*dir, vmi);
+  } else if (const auto *value{
+                 std::get_if<parser::OmpTraitSelectorName::Value>(&name.u)}) {
+    // SIMD is parsed as a predefined selector name because it can also take
+    // clause properties, unlike the other construct selectors.
+    if (*value == parser::OmpTraitSelectorName::Value::Simd) {
+      AppendConstructTraitsForDirective(llvm::omp::Directive::OMPD_simd, vmi);
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MattPD wrote:

Could `collectEnclosingConstructTraits` also supply the SIMD trait? `DECLARE VARIANT` uses `AppendConstructTraitsForSelector`, but the lowering collector never records `omp.simd`.

Save this as `repro.f90` and run `flang -fc1 -fopenmp -fopenmp-version=52 -emit-hlfir -o - repro.f90`. Revision `7f525837ea63` emits `fir.call @_QMmPbase` inside `omp.simd`, whereas [the base revision](https://github.com/llvm/llvm-project/commit/89082772bed1ed16c0311b12147a96c35bb063d8) emits `fir.call @_QMmPsimd_var`. The call should select the SIMD variant. Please cover this inside-SIMD case alongside the correctly fixed outside-SIMD case.

```fortran
module m
contains
  subroutine base(x)
    !$omp declare variant(simd_var) match(construct={simd})
    real :: x
    x = x + 1.0
  end subroutine
  subroutine simd_var(x)
    real :: x
    x = x + 2.0
  end subroutine
end module
subroutine test(a, n)
  use m
  integer :: n, i
  real :: a(n)
  !$omp simd
  do i = 1, n
    call base(a(i))
  end do
end subroutine
```

https://github.com/llvm/llvm-project/pull/219014