[flang][OpenMP] Allow structure component in task depend clauses

[ergawy]

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).

[llvmbot]

@llvm/pr-subscribers-flang-openmp
@llvm/pr-subscribers-flang-semantics

@llvm/pr-subscribers-flang-fir-hlfir

Author: Kareem Ergawy (ergawy)

Changes

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).

---

Full diff: https://github.com/llvm/llvm-project/pull/141923.diff

5 Files Affected:

• (modified) flang/include/flang/Evaluate/tools.h (+10)
• (modified) flang/lib/Lower/OpenMP/ClauseProcessor.cpp (+5)
• (modified) flang/lib/Semantics/check-omp-structure.cpp (+2-6)
• (added) flang/test/Lower/OpenMP/task-depend-structure-component.f90 (+21)
• (removed) flang/test/Semantics/OpenMP/depend02.f90 (-49)

diff --git a/flang/include/flang/Evaluate/tools.h b/flang/include/flang/Evaluate/tools.h
index 7f2e91ae128bd..4efd88b13183f 100644
--- a/flang/include/flang/Evaluate/tools.h
+++ b/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 isStructureCompnent(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)}) {
diff --git a/flang/lib/Lower/OpenMP/ClauseProcessor.cpp b/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
index ebdda9885d5c2..8506d562c5094 100644
--- a/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
+++ b/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
@@ -944,6 +944,11 @@ bool ClauseProcessor::processDepend(lower::SymMap &symMap,
               converter.getCurrentLocation(), converter, expr, symMap, stmtCtx);
           dependVar = entity.getBase();
         }
+      } else if (evaluate::isStructureCompnent(*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);
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index bda0d62829506..a3eeac4524eff 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -5493,12 +5493,8 @@ 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,
diff --git a/flang/test/Lower/OpenMP/task-depend-structure-component.f90 b/flang/test/Lower/OpenMP/task-depend-structure-component.f90
new file mode 100644
index 0000000000000..7cf6dbfac2729
--- /dev/null
+++ b/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: }
diff --git a/flang/test/Semantics/OpenMP/depend02.f90 b/flang/test/Semantics/OpenMP/depend02.f90
deleted file mode 100644
index 76c02c8f9cbab..0000000000000
--- a/flang/test/Semantics/OpenMP/depend02.f90
+++ /dev/null
@@ -1,49 +0,0 @@
-! RUN: %python %S/../test_errors.py %s %flang -fopenmp
-! OpenMP Version 4.5
-! 2.13.9 Depend Clause
-! 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
-
-subroutine vec_mult(N)
-  implicit none
-  integer :: i, N
-  real, allocatable :: p(:), v1(:), v2(:)
-
-  type my_type
-    integer :: a(10)
-  end type my_type
-
-  type(my_type) :: my_var
-  allocate( p(N), v1(N), v2(N) )
-
-  !$omp parallel num_threads(2)
-  !$omp single
-
-  !$omp task depend(out:v1)
-  call init(v1, N)
-  !$omp end task
-
-  !$omp task depend(out:v2)
-  call init(v2, N)
-  !$omp end task
-
-  !ERROR: 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
-  !$omp target nowait depend(in:v1,v2, my_var%a) depend(out:p) &
-  !$omp& map(to:v1,v2) map(from: p)
-  !$omp parallel do
-  do i=1,N
-    p(i) = v1(i) * v2(i)
-  end do
-  !$omp end target
-
-  !$omp task depend(in:p)
-  call output(p, N)
-  !$omp end task
-
-  !$omp end single
-  !$omp end parallel
-
-  deallocate( p, v1, v2 )
-
-end subroutine

[tblah]

LGTM, thanks!