[flang][OpenMP] Error out when CHARACTER type is used in atomic constructs

flang/lib/Lower/DirectivesCommon.h

@@ -126,12 +126,8 @@ static void processOmpAtomicTODO(mlir::Type elementType,
     return;
   if constexpr (std::is_same<AtomicListT,
                              Fortran::parser::OmpAtomicClauseList>()) {
-    // Based on assertion for supported element types in OMPIRBuilder.cpp
-    // createAtomicRead
-    mlir::Type unwrappedEleTy = fir::unwrapRefType(elementType);
-    bool supportedAtomicType = fir::isa_trivial(unwrappedEleTy);
-    if (!supportedAtomicType)
-      TODO(loc, "Unsupported atomic type");
+    assert(fir::isa_trivial(fir::unwrapRefType(elementType)) &&
+           "is supported type for omp atomic");
   }
 }
 

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

@@ -1888,16 +1888,21 @@ inline void OmpStructureChecker::ErrIfLHSAndRHSSymbolsMatch(
 inline void OmpStructureChecker::ErrIfNonScalarAssignmentStmt(
     const parser::Variable &var, const parser::Expr &expr) {
   // Err out if either the variable on the LHS or the expression on the RHS of
-  // the assignment statement are non-scalar (i.e. have rank > 0)
+  // the assignment statement are non-scalar (i.e. have rank > 0 or is of
+  // CHARACTER type)
   const auto *e{GetExpr(context_, expr)};
   const auto *v{GetExpr(context_, var)};
   if (e && v) {
-    if (e->Rank() != 0)
+    if (e->Rank() != 0 ||
+        (e->GetType().has_value() &&
+            e->GetType().value().category() == common::TypeCategory::Character))
       context_.Say(expr.source,
           "Expected scalar expression "
           "on the RHS of atomic assignment "
           "statement"_err_en_US);
-    if (v->Rank() != 0)
+    if (v->Rank() != 0 ||
+        (v->GetType().has_value() &&
+            v->GetType()->category() == common::TypeCategory::Character))
       context_.Say(var.GetSource(),
           "Expected scalar variable "
           "on the LHS of atomic assignment "
@@ -2008,12 +2013,16 @@ void OmpStructureChecker::CheckAtomicUpdateStmt(
       expr.u);
   if (const auto *e{GetExpr(context_, expr)}) {
     const auto *v{GetExpr(context_, var)};
-    if (e->Rank() != 0)
+    if (e->Rank() != 0 ||
+        (e->GetType().has_value() &&
+            e->GetType().value().category() == common::TypeCategory::Character))
       context_.Say(expr.source,
           "Expected scalar expression "
           "on the RHS of atomic update assignment "
           "statement"_err_en_US);
-    if (v->Rank() != 0)
+    if (v->Rank() != 0 ||
+        (v->GetType().has_value() &&
+            v->GetType()->category() == common::TypeCategory::Character))
       context_.Say(var.GetSource(),
           "Expected scalar variable "
           "on the LHS of atomic update assignment "

flang/test/Semantics/OpenMP/atomic02.f90

@@ -32,6 +32,7 @@ program OmpAtomic
    a = a**4
    !$omp atomic
    !ERROR: Invalid or missing operator in atomic update statement
+   !ERROR: Expected scalar expression on the RHS of atomic update assignment statement
    c = c//d
    !$omp atomic
    !ERROR: Atomic update statement should be of form `l = l operator expr` OR `l = expr operator l`
@@ -78,6 +79,7 @@ program OmpAtomic
    a = a**4
    !$omp atomic update
    !ERROR: Invalid or missing operator in atomic update statement
+   !ERROR: Expected scalar expression on the RHS of atomic update assignment statement
    c = c//d
    !$omp atomic update
    !ERROR: Atomic update statement should be of form `l = l operator expr` OR `l = expr operator l`

flang/test/Semantics/OpenMP/omp-atomic-assignment-stmt.f90

@@ -14,6 +14,7 @@ program sample
         integer :: m
     endtype
     type(sample_type) :: z
+    character :: l, r
     !$omp atomic read
         v = x
 
@@ -148,4 +149,14 @@ program sample
         y(1) = y(1) + 1
         x = y(2)
     !$omp end atomic
+
+    !$omp atomic read
+    !ERROR: Expected scalar variable on the LHS of atomic assignment statement
+    !ERROR: Expected scalar expression on the RHS of atomic assignment statement
+        l = r
+
+    !$omp atomic write
+    !ERROR: Expected scalar variable on the LHS of atomic assignment statement
+    !ERROR: Expected scalar expression on the RHS of atomic assignment statement
+        l = r
 end program