[flang][OpenMP] Allow structure component in task depend clauses (#141923)

Even though the spec (version 5.2) prohibits strcuture components from
being specified in `depend` clauses, this restriction is not sensible.

This PR rectifies the issue by lifting that restriction and allowing
structure components in `depend` clauses (which is allowed by OpenMP
6.0).

Author: ergawy

flang/include/flang/Evaluate/tools.h

@@ -414,6 +414,16 @@ const Symbol *IsArrayElement(const Expr<T> &expr, bool intoSubstring = true,
   return nullptr;
 }
 
+template <typename T>
+bool isStructureComponent(const Fortran::evaluate::Expr<T> &expr) {
+  if (auto dataRef{ExtractDataRef(expr, /*intoSubstring=*/false)}) {
+    const Fortran::evaluate::DataRef *ref{&*dataRef};
+    return std::holds_alternative<Fortran::evaluate::Component>(ref->u);
+  }
+
+  return false;
+}
+
 template <typename A>
 std::optional<NamedEntity> ExtractNamedEntity(const A &x) {
   if (auto dataRef{ExtractDataRef(x)}) {

flang/lib/Lower/OpenMP/ClauseProcessor.cpp

@@ -947,6 +947,11 @@ bool ClauseProcessor::processDepend(lower::SymMap &symMap,
               converter.getCurrentLocation(), converter, expr, symMap, stmtCtx);
           dependVar = entity.getBase();
         }
+      } else if (evaluate::isStructureComponent(*object.ref())) {
+        SomeExpr expr = *object.ref();
+        hlfir::EntityWithAttributes entity = convertExprToHLFIR(
+            converter.getCurrentLocation(), converter, expr, symMap, stmtCtx);
+        dependVar = entity.getBase();
       } else {
         semantics::Symbol *sym = object.sym();
         dependVar = converter.getSymbolAddress(*sym);

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

@@ -5494,12 +5494,8 @@ void OmpStructureChecker::CheckDependList(const parser::DataRef &d) {
             // Check if the base element is valid on Depend Clause
             CheckDependList(elem.value().base);
           },
-          [&](const common::Indirection<parser::StructureComponent> &) {
-            context_.Say(GetContext().clauseSource,
-                "A variable that is part of another variable "
-                "(such as an element of a structure) but is not an array "
-                "element or an array section cannot appear in a DEPEND "
-                "clause"_err_en_US);
+          [&](const common::Indirection<parser::StructureComponent> &comp) {
+            CheckDependList(comp.value().base);
           },
           [&](const common::Indirection<parser::CoindexedNamedObject> &) {
             context_.Say(GetContext().clauseSource,

flang/test/Lower/OpenMP/task-depend-structure-component.f90

@@ -0,0 +1,21 @@
+! RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - | FileCheck %s
+
+subroutine depend
+   type :: my_struct
+       integer :: my_component(10)
+   end type
+
+   type(my_struct) :: my_var
+
+   !$omp task depend(in:my_var%my_component)
+   !$omp end task
+end subroutine depend
+
+! CHECK: %[[VAR_ALLOC:.*]] = fir.alloca !fir.type<{{.*}}my_struct{{.*}}> {bindc_name = "my_var", {{.*}}}
+! CHECK: %[[VAR_DECL:.*]]:2 = hlfir.declare %[[VAR_ALLOC]]
+
+! CHECK: %[[COMP_SELECTOR:.*]] = hlfir.designate %[[VAR_DECL]]#0{"my_component"}
+
+! CHECK: omp.task depend(taskdependin -> %[[COMP_SELECTOR]] : {{.*}}) {
+! CHECK:   omp.terminator
+! CHECK: }