Add error for nesting of non loop transformation constructs

Author: Stylie777

flang/lib/Semantics/canonicalize-omp.cpp

@@ -164,30 +164,34 @@ class CanonicalizationOfOmp {
             std::get<parser::OmpBeginLoopDirective>(ompLoopCons->t);
         auto &beginLoopDirective =
         std::get<parser::OmpLoopDirective>(beginDirective.t);
-        // iterate through the remaining block items to find the end directive for the unroll/tile directive.
-        parser::Block::iterator endIt;
-        endIt = nextIt;
-        while(endIt != block.end()) {
-          if (auto *endDir{
-            GetConstructIf<parser::OmpEndLoopDirective>(*endIt)}) {
-              auto &endLoopDirective = std::get<parser::OmpLoopDirective>(endDir->t);
-              if(endLoopDirective.v == dir.v) {
-                std::get<std::optional<parser::OmpEndLoopDirective>>(x.t) =
-                std::move(*endDir);
-                endIt = block.erase(endIt);
-                continue;
+        if ((beginLoopDirective.v == llvm::omp::Directive::OMPD_unroll ||
+          beginLoopDirective.v == llvm::omp::Directive::OMPD_tile)) {
+          // iterate through the remaining block items to find the end directive for the unroll/tile directive.
+          parser::Block::iterator endIt;
+          endIt = nextIt;
+          while(endIt != block.end()) {
+            if (auto *endDir{
+              GetConstructIf<parser::OmpEndLoopDirective>(*endIt)}) {
+                auto &endLoopDirective = std::get<parser::OmpLoopDirective>(endDir->t);
+                if(endLoopDirective.v == dir.v) {
+                  std::get<std::optional<parser::OmpEndLoopDirective>>(x.t) =
+                  std::move(*endDir);
+                  endIt = block.erase(endIt);
+                  continue;
+                }
               }
+              ++endIt;
             }
-            ++endIt;
-          }
-        if ((beginLoopDirective.v == llvm::omp::Directive::OMPD_unroll ||
-            beginLoopDirective.v == llvm::omp::Directive::OMPD_tile)) {
           RewriteOpenMPLoopConstruct(*ompLoopCons, block, nextIt);
           auto &ompLoop = std::get<std::optional<std::variant<parser::DoConstruct, common::Indirection<parser::OpenMPLoopConstruct>>>>(x.t);
           ompLoop = std::optional<std::variant<parser::DoConstruct, common::Indirection<parser::OpenMPLoopConstruct>>>{
             std::variant<parser::DoConstruct, common::Indirection<parser::OpenMPLoopConstruct>>{
             common::Indirection{std::move(*ompLoopCons)}}};
           nextIt = block.erase(nextIt);
+        } else {
+          messages_.Say(dir.source,
+            "Only OpenMP Loop Transformation Constructs can be nested within OpenMPLoopConstruct's"_err_en_US,
+            parser::ToUpperCaseLetters(dir.source.ToString()));
         }
       } else {
         missingDoConstruct(dir);

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

@@ -781,12 +781,6 @@ void OmpStructureChecker::Enter(const parser::OpenMPLoopConstruct &x) {
       (beginDir.v == llvm::omp::Directive::OMPD_distribute_simd)) {
     CheckDistLinear(x);
   }
-  if (beginDir.v == llvm::omp::Directive::OMPD_tile) {
-    const auto &clauses{std::get<parser::OmpClauseList>(beginLoopDir.t)};
-    for (auto &clause : clauses.v) {
-
-    }
-  }
 }
 const parser::Name OmpStructureChecker::GetLoopIndex(
     const parser::DoConstruct *x) {

flang/test/Semantics/OpenMP/loop-transformation-construct01.f90

@@ -26,3 +26,21 @@ subroutine loop_transformation_construct2
   !ERROR: The END TILE directive must follow the DO loop associated with the loop construct
   !$omp end tile
 end subroutine
+
+subroutine loop_transformation_construct2
+  implicit none
+  integer :: i = 5
+  integer :: y
+  integer :: v(i)
+
+  !$omp do
+  !ERROR: Only OpenMP Loop Transformation Constructs can be nested within OpenMPLoopConstruct's
+  !$omp parallel do
+  do x = 1, i
+    v(x) = x(x) * 2
+  end do
+  !! This error occurs because the `parallel do` end directive never gets matched.
+  !ERROR: The END PARALLEL DO directive must follow the DO loop associated with the loop construct
+  !$omp end parallel do
+  !$omp end do
+end subroutine