Address review comments and rebase.

Author: raghavendhra

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

@@ -824,8 +824,7 @@ void OmpStructureChecker::CheckTargetNest(const parser::OpenMPConstruct &c) {
                 std::get<parser::OmpBeginBlockDirective>(c.t)};
             const auto &beginDir{
                 std::get<parser::OmpBlockDirective>(beginBlockDir.t)};
-            if (beginDir.v == llvm::omp::Directive::OMPD_target_data ||
-                llvm::omp::allTargetSet.test(beginDir.v)) {
+            if (beginDir.v == llvm::omp::Directive::OMPD_target_data) {
               eligibleTarget = false;
               ineligibleTargetDir = beginDir.v;
             }
@@ -849,11 +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(
@@ -1067,28 +1076,14 @@ 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);
   }
 
   if (CurrentDirectiveIsNested()) {
     if (llvm::omp::topTeamsSet.test(GetContextParent().directive)) {
       HasInvalidTeamsNesting(beginDir.v, beginDir.source);
     }
-    if ((llvm::omp::allTargetSet.test(GetContext().directive) ||
-            (GetContext().directive ==
-                llvm::omp::Directive::OMPD_target_data)) &&
-        (llvm::omp::allTargetSet.test(GetContextParent().directive) ||
-            (GetContextParent().directive ==
-                llvm::omp::Directive::OMPD_target_data))) {
-      context_.Warn(common::UsageWarning::OpenMPUsage,
-          parser::FindSourceLocation(x),
-          "If %s directive is nested inside %s region, the behaviour is unspecified"_port_en_US,
-          parser::ToUpperCaseLetters(
-              getDirectiveName(GetContext().directive).str()),
-          parser::ToUpperCaseLetters(
-              getDirectiveName(GetContextParent().directive).str()));
-    }
     if (GetContext().directive == llvm::omp::Directive::OMPD_master) {
       CheckMasterNesting(x);
     }
@@ -1164,7 +1159,7 @@ 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-simd.f90

@@ -166,7 +166,6 @@ SUBROUTINE NESTED_BAD(N)
       end do
       !$omp end task
       !ERROR: The only OpenMP constructs that can be encountered during execution of a 'SIMD' region are the `ATOMIC` construct, the `LOOP` construct, the `SIMD` construct, the `SCAN` construct and the `ORDERED` construct with the `SIMD` clause.
-      !ERROR: If TARGET directive is nested inside TARGET SIMD region, the behaviour is unspecified
       !$omp target 
       do J = 1, N
         K = 2

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

@@ -53,7 +53,7 @@ program main
   n1 = 10
   n2 = 10
   !$omp target teams map(to:a)
-  !PORTABILITY: If TARGET DATA directive is nested inside TARGET TEAMS region, the behaviour is unspecified
+  !PORTABILITY: If TARGET DATA directive is nested inside TARGET region, the behaviour is unspecified
   !$omp target data map(n1,n2)
   do i=1, n1
      do j=1, n2