[flang][OpenMP] Don't try to privatize FORALL/DO CONCURRENT indices (#123341)

FORALL/DO CONCURRENT indices have predetermined private DSA (OpenMP 5.2
5.1.1).

As FORALL/DO CONCURRENT indices are defined in the construct itself, and
OpenMP
directives may not appear in it, they are already private and don't need
to be modified.

Fixes #100919
Fixes #120023
Fixes #123537

Author: luporl

flang/lib/Semantics/resolve-directives.cpp

@@ -1777,28 +1777,13 @@ void OmpAttributeVisitor::ResolveSeqLoopIndexInParallelOrTaskConstruct(
 // Use of DO CONCURRENT inside OpenMP construct is unspecified behavior
 // till OpenMP-5.0 standard.
 // In above both cases we skip the privatization of iteration variables.
-// [OpenMP 5.1] DO CONCURRENT indices are private
 bool OmpAttributeVisitor::Pre(const parser::DoConstruct &x) {
   if (!dirContext_.empty() && GetContext().withinConstruct) {
     llvm::SmallVector<const parser::Name *> ivs;
     if (x.IsDoNormal()) {
       const parser::Name *iv{GetLoopIndex(x)};
       if (iv && iv->symbol)
         ivs.push_back(iv);
-    } else if (x.IsDoConcurrent()) {
-      const Fortran::parser::LoopControl *loopControl = &*x.GetLoopControl();
-      const Fortran::parser::LoopControl::Concurrent &concurrent =
-          std::get<Fortran::parser::LoopControl::Concurrent>(loopControl->u);
-      const Fortran::parser::ConcurrentHeader &concurrentHeader =
-          std::get<Fortran::parser::ConcurrentHeader>(concurrent.t);
-      const std::list<Fortran::parser::ConcurrentControl> &controls =
-          std::get<std::list<Fortran::parser::ConcurrentControl>>(
-              concurrentHeader.t);
-      for (const auto &control : controls) {
-        const parser::Name *iv{&std::get<0>(control.t)};
-        if (iv && iv->symbol)
-          ivs.push_back(iv);
-      }
     }
     ordCollapseLevel--;
     for (auto iv : ivs) {
@@ -1810,9 +1795,6 @@ bool OmpAttributeVisitor::Pre(const parser::DoConstruct &x) {
       if (ordCollapseLevel) {
         if (const auto *details{iv->symbol->detailsIf<HostAssocDetails>()}) {
           const Symbol *tpSymbol = &details->symbol();
-          // TODO: DoConcurrent won't capture the following check because a new
-          // symbol is declared in ResolveIndexName(), which will not have the
-          // OmpThreadprivate flag.
           if (tpSymbol->test(Symbol::Flag::OmpThreadprivate)) {
             context_.Say(iv->source,
                 "Loop iteration variable %s is not allowed in THREADPRIVATE."_err_en_US,
@@ -2119,6 +2101,7 @@ static bool IsPrivatizable(const Symbol *sym) {
           *sym) && /* OpenMP 5.2, 5.1.1: Assumed-size arrays are shared*/
       !sym->owner().IsDerivedType() &&
       sym->owner().kind() != Scope::Kind::ImpliedDos &&
+      sym->owner().kind() != Scope::Kind::Forall &&
       !sym->detailsIf<semantics::AssocEntityDetails>() &&
       !sym->detailsIf<semantics::NamelistDetails>() &&
       (!misc ||

flang/test/Semantics/OpenMP/doconcurrent01.f90

@@ -1,15 +1,19 @@
 ! RUN: %python %S/../test_symbols.py %s %flang_fc1 -fopenmp
 
-! OpenMP 5.1.1
-! DO Concurrent indices are private
+! OpenMP 5.2 5.1.1 Variables Referenced in a Construct
+! DO CONCURRENT indices have predetermined private DSA.
+!
+! As DO CONCURRENT indices are defined in the construct itself, and OpenMP
+! directives may not appear in it, they are already private.
+! Check that index symbols are not modified.
 
 !DEF: /private_iv (Subroutine)Subprogram
 subroutine private_iv
    !DEF: /private_iv/i ObjectEntity INTEGER(4)
    integer i
    !$omp parallel default(private)
    !$omp single
-   !DEF: /private_iv/OtherConstruct1/i (OmpPrivate, OmpPreDetermined) HostAssoc INTEGER(4)
+   !DEF: /private_iv/OtherConstruct1/OtherConstruct1/Forall1/i ObjectEntity INTEGER(4)
    do concurrent(i=1:2)
    end do
    !$omp end single

flang/test/Semantics/OpenMP/forall.f90

@@ -0,0 +1,32 @@
+! RUN: %python %S/../test_symbols.py %s %flang_fc1 -fopenmp
+
+! OpenMP 5.2 5.1.1 Variables Referenced in a Construct
+! FORALL indices have predetermined private DSA.
+!
+! As FORALL indices are defined in the construct itself, and OpenMP
+! directives may not appear in it, they are already private.
+! Check that index symbols are not modified.
+
+  !DEF: /MainProgram1/a ObjectEntity INTEGER(4)
+  !DEF: /MainProgram1/b ObjectEntity INTEGER(4)
+  integer a(5), b(5)
+
+  !REF: /MainProgram1/a
+  a = 0
+  !REF: /MainProgram1/b
+  b = 0
+
+  !$omp parallel
+    !DEF: /MainProgram1/OtherConstruct1/Forall1/i (Implicit) ObjectEntity INTEGER(4)
+    !DEF: /MainProgram1/OtherConstruct1/a HostAssoc INTEGER(4)
+    !DEF: /MainProgram1/OtherConstruct1/b HostAssoc INTEGER(4)
+    forall(i = 1:5) a(i) = b(i) * 2
+  !$omp end parallel
+
+  !$omp parallel default(private)
+    !DEF: /MainProgram1/OtherConstruct2/Forall1/i (Implicit) ObjectEntity INTEGER(4)
+    !DEF: /MainProgram1/OtherConstruct2/a (OmpPrivate) HostAssoc INTEGER(4)
+    !DEF: /MainProgram1/OtherConstruct2/b (OmpPrivate) HostAssoc INTEGER(4)
+    forall(i = 1:5) a(i) = b(i) * 2
+  !$omp end parallel
+end program