[Flang][OpenMP] Restrict certain loops not allowed in associated loops

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

@@ -84,21 +84,34 @@ class OmpWorkshareBlockChecker {
   parser::CharBlock source_;
 };
 
-class OmpCycleAndExitChecker {
+class AssociatedLoopChecker {
 public:
-  OmpCycleAndExitChecker(SemanticsContext &context, std::int64_t level)
+  AssociatedLoopChecker(SemanticsContext &context, std::int64_t level)
       : context_{context}, level_{level} {}
 
   template <typename T> bool Pre(const T &) { return true; }
   template <typename T> void Post(const T &) {}
 
   bool Pre(const parser::DoConstruct &dc) {
     level_--;
-    const auto &constructName{std::get<0>(std::get<0>(dc.t).statement.t)};
+    const auto &doStmt{
+        std::get<parser::Statement<parser::NonLabelDoStmt>>(dc.t)};
+    const auto &constructName{
+        std::get<std::optional<parser::Name>>(doStmt.statement.t)};
     if (constructName) {
       constructNamesAndLevels_.emplace(
           constructName.value().ToString(), level_);
     }
+    if (level_ >= 0) {
+      if (dc.IsDoWhile()) {
+        context_.Say(doStmt.source,
+            "The associated loop of a loop-associated directive cannot be a DO WHILE."_err_en_US);
+      }
+      if (!dc.GetLoopControl()) {
+        context_.Say(doStmt.source,
+            "The associated loop of a loop-associated directive cannot be a DO without control."_err_en_US);
+      }
+    }
     return true;
   }
 
@@ -450,9 +463,8 @@ void OmpStructureChecker::Enter(const parser::OpenMPLoopConstruct &x) {
     const auto &doBlock{std::get<parser::Block>(doConstruct->t)};
     CheckNoBranching(doBlock, beginDir.v, beginDir.source);
   }
-  CheckDoWhile(x);
   CheckLoopItrVariableIsInt(x);
-  CheckCycleConstraints(x);
+  CheckAssociatedLoopConstraints(x);
   HasInvalidDistributeNesting(x);
   if (CurrentDirectiveIsNested() &&
       llvm::omp::topTeamsSet.test(GetContextParent().directive)) {
@@ -478,21 +490,6 @@ void OmpStructureChecker::SetLoopInfo(const parser::OpenMPLoopConstruct &x) {
     }
   }
 }
-void OmpStructureChecker::CheckDoWhile(const parser::OpenMPLoopConstruct &x) {
-  const auto &beginLoopDir{std::get<parser::OmpBeginLoopDirective>(x.t)};
-  const auto &beginDir{std::get<parser::OmpLoopDirective>(beginLoopDir.t)};
-  if (beginDir.v == llvm::omp::Directive::OMPD_do) {
-    if (const auto &doConstruct{
-            std::get<std::optional<parser::DoConstruct>>(x.t)}) {
-      if (doConstruct.value().IsDoWhile()) {
-        const auto &doStmt{std::get<parser::Statement<parser::NonLabelDoStmt>>(
-            doConstruct.value().t)};
-        context_.Say(doStmt.source,
-            "The DO loop cannot be a DO WHILE with DO directive."_err_en_US);
-      }
-    }
-  }
-}
 
 void OmpStructureChecker::CheckLoopItrVariableIsInt(
     const parser::OpenMPLoopConstruct &x) {
@@ -647,8 +644,8 @@ std::int64_t OmpStructureChecker::GetOrdCollapseLevel(
   const auto &beginLoopDir{std::get<parser::OmpBeginLoopDirective>(x.t)};
   const auto &clauseList{std::get<parser::OmpClauseList>(beginLoopDir.t)};
   std::int64_t orderedCollapseLevel{1};
-  std::int64_t orderedLevel{0};
-  std::int64_t collapseLevel{0};
+  std::int64_t orderedLevel{1};
+  std::int64_t collapseLevel{1};
 
   for (const auto &clause : clauseList.v) {
     if (const auto *collapseClause{
@@ -672,10 +669,10 @@ std::int64_t OmpStructureChecker::GetOrdCollapseLevel(
   return orderedCollapseLevel;
 }
 
-void OmpStructureChecker::CheckCycleConstraints(
+void OmpStructureChecker::CheckAssociatedLoopConstraints(
     const parser::OpenMPLoopConstruct &x) {
   std::int64_t ordCollapseLevel{GetOrdCollapseLevel(x)};
-  OmpCycleAndExitChecker checker{context_, ordCollapseLevel};
+  AssociatedLoopChecker checker{context_, ordCollapseLevel};
   parser::Walk(x, checker);
 }
 

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

@@ -186,7 +186,7 @@ class OmpStructureChecker
 
   void CheckLoopItrVariableIsInt(const parser::OpenMPLoopConstruct &x);
   void CheckDoWhile(const parser::OpenMPLoopConstruct &x);
-  void CheckCycleConstraints(const parser::OpenMPLoopConstruct &x);
+  void CheckAssociatedLoopConstraints(const parser::OpenMPLoopConstruct &x);
   template <typename T, typename D> bool IsOperatorValid(const T &, const D &);
   void CheckAtomicMemoryOrderClause(
       const parser::OmpAtomicClauseList *, const parser::OmpAtomicClauseList *);

flang/test/Semantics/OpenMP/clause-validity01.f90

@@ -173,6 +173,7 @@
   outer: do i=0, 10
     inner: do j=1, 10
       exit
+      !ERROR: EXIT statement terminates associated loop of an OpenMP DO construct
       exit outer
       !ERROR: EXIT to construct 'outofparallel' outside of PARALLEL construct is not allowed
       !ERROR: EXIT to construct 'outofparallel' outside of DO construct is not allowed

flang/test/Semantics/OpenMP/do-collapse.f90

@@ -26,6 +26,7 @@ program omp_doCollapse
   !$omp parallel do collapse(2)
     do i = 1, 3
       !ERROR: Loop control is not present in the DO LOOP
+      !ERROR: The associated loop of a loop-associated directive cannot be a DO without control.
       do
       end do
     end do

flang/test/Semantics/OpenMP/do09.f90

@@ -6,15 +6,15 @@
 program omp_do
   integer ::  i = 0,k
   !$omp do
-  !ERROR: The DO loop cannot be a DO WHILE with DO directive.
+  !ERROR: The associated loop of a loop-associated directive cannot be a DO WHILE.
   do while (i <= 10)
     print *, "it",i
     i = i+1
   end do
   !$omp end do
 
   !$omp do
-  !ERROR: The DO loop cannot be a DO WHILE with DO directive.
+  !ERROR: The associated loop of a loop-associated directive cannot be a DO WHILE.
   do while (i <= 10)
     do while (j <= 10)
       print *, "it",k