[Flang][OpenMP] Fix issue with named constants in SHARED and FIRSTPRIVATE clauses (llvm#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.

Author: mjklemm

flang/lib/Semantics/check-omp-structure.cpp

@@ -2560,11 +2560,24 @@ 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) &&
+          !(IsNamedConstant(*symbol) && SharedOrFirstprivate)) {
         deferredNonVariables_.insert({symbol, source});
       }
     }

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