[flang-commits] [flang] 4b33d45 - [Flang][OpenMP] Fix visibility of user-defined reductions for derived types and module imports (#180552)

[via flang-commits]

Author: CHANDRA GHALE
Date: 2026-02-11T12:06:37+05:30
New Revision: 4b33d45809e175f9bb0a74faab049d7fd229e45e

URL: https://github.com/llvm/llvm-project/commit/4b33d45809e175f9bb0a74faab049d7fd229e45e
DIFF: https://github.com/llvm/llvm-project/commit/4b33d45809e175f9bb0a74faab049d7fd229e45e.diff

LOG: [Flang][OpenMP] Fix visibility of user-defined reductions for derived types and module imports (#180552)

User-defined reductions declared in a module were not visible to
programs that imported the module via USE statements, causing valid code
to be incorrectly rejected. The reduction identifier defined in the
module scope wasn't being found during semantic analysis of the main
program.

Ref:
OpenMP Spec 5.1 
_"If a directive appears in the specification part of a module then the
behavior is as if that directive,
with the variables, types and procedures that have PRIVATE accessibility
omitted, appears in the
specification part of any compilation unit that references the module
unless otherwise specified "_

Fixes :
[https://github.com/llvm/llvm-project/issues/176279](https://github.com/llvm/llvm-project/issues/176279)

Co-authored-by: Chandra Ghale <ghale at pe31.hpc.amslabs.hpecorp.net>

Added: 
    flang/test/Semantics/OpenMP/declare-reduction-derived-module.f90

Modified: 
    flang/include/flang/Semantics/symbol.h
    flang/lib/Semantics/check-omp-structure.cpp

Removed: 
    


################################################################################
diff  --git a/flang/include/flang/Semantics/symbol.h b/flang/include/flang/Semantics/symbol.h
index 95efe1ae2bd5e..4c422ac5f471a 100644
--- a/flang/include/flang/Semantics/symbol.h
+++ b/flang/include/flang/Semantics/symbol.h
@@ -764,6 +764,22 @@ class UserReductionDetails {
         return true;
       }
     }
+    // For derived and class-derived types, match on the type symbol pointer.
+    if (type.category() == DeclTypeSpec::TypeDerived ||
+        type.category() == DeclTypeSpec::ClassDerived) {
+      const auto &rhs = type.derivedTypeSpec();
+      const auto &rhsSym = rhs.typeSymbol();
+      for (auto t : typeList_) {
+        if (t->category() == DeclTypeSpec::TypeDerived ||
+            t->category() == DeclTypeSpec::ClassDerived) {
+          const auto &lhs = t->derivedTypeSpec();
+          const auto &lhsSym = lhs.typeSymbol();
+          if (&lhsSym == &rhsSym) {
+            return true;
+          }
+        }
+      }
+    }
     return false;
   }
 

diff  --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 5c4b5bb756734..0e004a8e26501 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -3691,6 +3691,20 @@ static bool CheckSymbolSupportsType(const Scope &scope,
       return reductionDetails->SupportsType(type);
     }
   }
+  // Look through module scopes in the global scope.
+  // This covers reductions declared in a module and used via USE association
+  const SemanticsContext &semCtx{scope.context()};
+  Scope &global = const_cast<SemanticsContext &>(semCtx).globalScope();
+  for (const Scope &child : global.children()) {
+    if (child.kind() == Scope::Kind::Module) {
+      if (const auto *symbol{child.FindSymbol(name)}) {
+        if (const auto *reductionDetails{
+                symbol->detailsIf<UserReductionDetails>()}) {
+          return reductionDetails->SupportsType(type);
+        }
+      }
+    }
+  }
   return false;
 }
 

diff  --git a/flang/test/Semantics/OpenMP/declare-reduction-derived-module.f90 b/flang/test/Semantics/OpenMP/declare-reduction-derived-module.f90
new file mode 100644
index 0000000000000..342301ba2a8da
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/declare-reduction-derived-module.f90
@@ -0,0 +1,30 @@
+! RUN: %flang_fc1 -fdebug-dump-symbols -fopenmp -fopenmp-version=50 %s | FileCheck %s
+module mod
+  type t
+     integer::i=0
+  end type t
+!$omp declare reduction (+:t:omp_out%i=omp_out%i+omp_in%i) &
+!$omp         initializer(omp_priv%i=0)
+end module mod
+
+!CHECK: Module scope: mod
+!CHECK: op.+, PUBLIC: UserReductionDetails TYPE(t)
+!CHECK: t, PUBLIC: DerivedType components: i
+
+program main
+  use mod
+  integer::i
+  type(t)::x1
+  x1%i=0
+!$omp parallel do reduction(+:x1)
+  do i=1,10
+     x1%i=x1%i+1
+  end do
+!$omp end parallel do
+  print *,'pass'
+end program main
+
+!CHECK: MainProgram scope: MAIN
+!CHECK: op.+: Use from op.+ in mod
+!CHECK: t: Use from t in mod
+!CHECK: x1 size=4 offset=4: ObjectEntity type: TYPE(t)