[flang-commits] [flang] [Flang][OpenMP] Fix issue with named constants in SHARED and FIRSTPRIVATE clauses (PR #154335)

[Michael Klemm via flang-commits]

https://github.com/mjklemm created https://github.com/llvm/llvm-project/pull/154335

The seemingly was a regression that prevented the usage of named constant (w/ PARAMETER attribute) in SHARED and FIRSTPRIVATE clauses.   This PR corrects that.

>From 9fd70ac26c725b405ad75e98c9524e0aa9e77919 Mon Sep 17 00:00:00 2001
From: Michael Klemm <michael.klemm at amd.com>
Date: Mon, 18 Aug 2025 23:13:01 +0200
Subject: [PATCH] [Flang][OpenMP] Fix issue with named constants not being
 allowed in shared and firstprivate

---
 flang/include/flang/Semantics/openmp-utils.h  |  1 +
 flang/lib/Semantics/check-omp-structure.cpp   | 15 ++++++-
 flang/lib/Semantics/openmp-utils.cpp          |  4 ++
 .../test/Semantics/OpenMP/named-constants.f90 | 44 +++++++++++++++++++
 4 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 flang/test/Semantics/OpenMP/named-constants.f90

diff --git a/flang/include/flang/Semantics/openmp-utils.h b/flang/include/flang/Semantics/openmp-utils.h
index 1c54124a5738a..df09e7a9e24b5 100644
--- a/flang/include/flang/Semantics/openmp-utils.h
+++ b/flang/include/flang/Semantics/openmp-utils.h
@@ -65,6 +65,7 @@ std::optional<parser::CharBlock> GetObjectSource(
 bool IsCommonBlock(const Symbol &sym);
 bool IsExtendedListItem(const Symbol &sym);
 bool IsVariableListItem(const Symbol &sym);
+bool IsNamedConstantListItem(const Symbol &sym);
 bool IsVarOrFunctionRef(const MaybeExpr &expr);
 
 bool IsMapEnteringType(parser::OmpMapType::Value type);
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index d9092565449da..5c3e6cad79c95 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -2561,11 +2561,24 @@ void OmpStructureChecker::Enter(const parser::OmpClause &x) {
     break;
   }
 
+  // Named constants are OK to be used within 'shared' and 'firstprivate'
+  // clauses.  The check for this happens a few lines below.
+  bool SharedOrFirstprivate = false;
+  switch (x.Id()) {
+  case llvm::omp::Clause::OMPC_shared:
+  case llvm::omp::Clause::OMPC_firstprivate:
+    SharedOrFirstprivate = true;
+    break;
+  default:
+    break;
+  }
+
   if (const parser::OmpObjectList *objList{GetOmpObjectList(x)}) {
     SymbolSourceMap symbols;
     GetSymbolsInObjectList(*objList, symbols);
     for (const auto &[symbol, source] : symbols) {
-      if (!IsVariableListItem(*symbol)) {
+      if (!IsVariableListItem(*symbol) &&
+          !(IsNamedConstantListItem(*symbol) && SharedOrFirstprivate)) {
         deferredNonVariables_.insert({symbol, source});
       }
     }
diff --git a/flang/lib/Semantics/openmp-utils.cpp b/flang/lib/Semantics/openmp-utils.cpp
index e8df346ccdc3e..663814b440034 100644
--- a/flang/lib/Semantics/openmp-utils.cpp
+++ b/flang/lib/Semantics/openmp-utils.cpp
@@ -130,6 +130,10 @@ bool IsVariableListItem(const Symbol &sym) {
   return evaluate::IsVariable(sym) || sym.attrs().test(Attr::POINTER);
 }
 
+bool IsNamedConstantListItem(const Symbol &sym) {
+  return sym.attrs().test(Attr::PARAMETER);
+}
+
 bool IsExtendedListItem(const Symbol &sym) {
   return IsVariableListItem(sym) || sym.IsSubprogram();
 }
diff --git a/flang/test/Semantics/OpenMP/named-constants.f90 b/flang/test/Semantics/OpenMP/named-constants.f90
new file mode 100644
index 0000000000000..ac0850066cebe
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/named-constants.f90
@@ -0,0 +1,44 @@
+!RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp
+
+module named_constants
+    implicit none
+contains
+    subroutine shrd()
+        implicit none
+        integer, parameter :: n = 7
+        real, parameter :: m = 7.0
+        logical, parameter :: l = .false.
+        integer, dimension(3), parameter :: a = [1, 2, 3]
+        ! no error expected
+        !$omp parallel shared(n, m, l, a)
+            print *, n, m, l, a
+        !$omp end parallel
+    end subroutine shrd
+
+    subroutine frstprvt()
+        implicit none
+        integer, parameter :: n = 7
+        real, parameter :: m = 7.0
+        logical, parameter :: l = .false.
+        integer, dimension(3), parameter :: a = [1, 2, 3]
+        ! no error expected
+        !$omp parallel firstprivate(n, m, l, a)
+            print *, n, m, l, a
+        !$omp end parallel
+    end subroutine frstprvt
+
+    subroutine prvt()
+        implicit none
+        integer, parameter :: n = 7
+        real, parameter :: m = 7.0
+        logical, parameter :: l = .false.
+        integer, dimension(3), parameter :: a = [1, 2, 3]
+        !ERROR: 'n' must be a variable
+        !ERROR: 'm' must be a variable
+        !ERROR: 'l' must be a variable
+        !ERROR: 'a' must be a variable
+        !$omp parallel private(n, m, l, a)
+            print *, n, m, l, a
+        !$omp end parallel
+    end subroutine prvt
+end module named_constants