[Flang] [Semantics] [OpenMP] Added missing semantic check with nested target region. (#115344)

Issue semantic warning for any combination of nested OMP TARGET
directives inside another OMP TARGET region.

This change would not affect OMP TARGET inside an OMP TARGET DATA.
However, it issues warning for OMP TARGET DATA inside an OMP TARGET
region.

Author: raghavendhra

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

@@ -848,11 +848,21 @@ void OmpStructureChecker::CheckTargetNest(const parser::OpenMPConstruct &c) {
                 },
                 c.u);
           },
+          [&](const parser::OpenMPLoopConstruct &c) {
+            const auto &beginLoopDir{
+                std::get<parser::OmpBeginLoopDirective>(c.t)};
+            const auto &beginDir{
+                std::get<parser::OmpLoopDirective>(beginLoopDir.t)};
+            if (llvm::omp::allTargetSet.test(beginDir.v)) {
+              eligibleTarget = false;
+              ineligibleTargetDir = beginDir.v;
+            }
+          },
           [&](const auto &c) {},
       },
       c.u);
   if (!eligibleTarget) {
-    context_.Warn(common::UsageWarning::Portability,
+    context_.Warn(common::UsageWarning::OpenMPUsage,
         parser::FindSourceLocation(c),
         "If %s directive is nested inside TARGET region, the behaviour is unspecified"_port_en_US,
         parser::ToUpperCaseLetters(
@@ -1068,7 +1078,7 @@ void OmpStructureChecker::Enter(const parser::OpenMPBlockConstruct &x) {
   CheckMatching<parser::OmpBlockDirective>(beginDir, endDir);
 
   PushContextAndClauseSets(beginDir.source, beginDir.v);
-  if (GetContext().directive == llvm::omp::Directive::OMPD_target) {
+  if (llvm::omp::allTargetSet.test(GetContext().directive)) {
     EnterDirectiveNest(TargetNest);
   }
 
@@ -1151,7 +1161,7 @@ void OmpStructureChecker::Leave(const parser::OpenMPBlockConstruct &) {
   if (GetDirectiveNest(TargetBlockOnlyTeams)) {
     ExitDirectiveNest(TargetBlockOnlyTeams);
   }
-  if (GetContext().directive == llvm::omp::Directive::OMPD_target) {
+  if (llvm::omp::allTargetSet.test(GetContext().directive)) {
     ExitDirectiveNest(TargetNest);
   }
   dirContext_.pop_back();

flang/test/Semantics/OpenMP/nested-target.f90

@@ -5,7 +5,7 @@
 ! 2.12.5 Target Construct
 
 program main
-  integer :: i, j, N = 10
+  integer :: i, j, N = 10, n1, n2, res(100)
   real :: a, arrayA(512), arrayB(512), ai(10)
   real, allocatable :: B(:)
 
@@ -50,4 +50,28 @@ program main
   !$omp end target
   deallocate(B)
 
+  n1 = 10
+  n2 = 10
+  !$omp target teams map(to:a)
+  !PORTABILITY: If TARGET DATA directive is nested inside TARGET region, the behaviour is unspecified
+  !$omp target data map(n1,n2)
+  do i=1, n1
+     do j=1, n2
+      res((i-1)*10+j) = i*j
+     end do
+  end do
+  !$omp end target data
+  !$omp end target teams
+
+  !$omp target teams map(to:a) map(from:n1,n2)
+  !PORTABILITY: If TARGET TEAMS DISTRIBUTE PARALLEL DO directive is nested inside TARGET region, the behaviour is unspecified
+  !$omp target teams distribute parallel do
+  do i=1, n1
+     do j=1, n2
+      res((i-1)*10+j) = i*j
+     end do
+  end do
+  !$omp end target teams distribute parallel do
+  !$omp end target teams
+
 end program main