[Flang][OpenMP] Add checks for EXIT from associated loops (#91315)

Extend the checker that deals with CYCLE to handle EXIT also. The
difference for EXIT is that it is not allowed to EXIT from the innermost
associated loops while it is OK to CYCLE in the innermost associated
loop. Also add an incrementer on leaving the DO loop for EXIT checks.

Author: kiranchandramohan

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

@@ -84,52 +84,69 @@ class OmpWorkshareBlockChecker {
   parser::CharBlock source_;
 };
 
-class OmpCycleChecker {
+class OmpCycleAndExitChecker {
 public:
-  OmpCycleChecker(SemanticsContext &context, std::int64_t cycleLevel)
-      : context_{context}, cycleLevel_{cycleLevel} {}
+  OmpCycleAndExitChecker(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) {
-    cycleLevel_--;
+    level_--;
     const auto &constructName{std::get<0>(std::get<0>(dc.t).statement.t)};
     if (constructName) {
       constructNamesAndLevels_.emplace(
-          constructName.value().ToString(), cycleLevel_);
+          constructName.value().ToString(), level_);
     }
     return true;
   }
 
+  void Post(const parser::DoConstruct &dc) { level_++; }
+
   bool Pre(const parser::CycleStmt &cyclestmt) {
     std::map<std::string, std::int64_t>::iterator it;
     bool err{false};
     if (cyclestmt.v) {
       it = constructNamesAndLevels_.find(cyclestmt.v->source.ToString());
       err = (it != constructNamesAndLevels_.end() && it->second > 0);
-    } else {
-      // If there is no label then the cycle statement is associated with the
-      // closest enclosing DO. Use its level for the checks.
-      err = cycleLevel_ > 0;
+    } else { // If there is no label then use the level of the last enclosing DO
+      err = level_ > 0;
     }
     if (err) {
-      context_.Say(*cycleSource_,
+      context_.Say(*source_,
           "CYCLE statement to non-innermost associated loop of an OpenMP DO "
           "construct"_err_en_US);
     }
     return true;
   }
 
+  bool Pre(const parser::ExitStmt &exitStmt) {
+    std::map<std::string, std::int64_t>::iterator it;
+    bool err{false};
+    if (exitStmt.v) {
+      it = constructNamesAndLevels_.find(exitStmt.v->source.ToString());
+      err = (it != constructNamesAndLevels_.end() && it->second >= 0);
+    } else { // If there is no label then use the level of the last enclosing DO
+      err = level_ >= 0;
+    }
+    if (err) {
+      context_.Say(*source_,
+          "EXIT statement terminates associated loop of an OpenMP DO "
+          "construct"_err_en_US);
+    }
+    return true;
+  }
+
   bool Pre(const parser::Statement<parser::ActionStmt> &actionstmt) {
-    cycleSource_ = &actionstmt.source;
+    source_ = &actionstmt.source;
     return true;
   }
 
 private:
   SemanticsContext &context_;
-  const parser::CharBlock *cycleSource_;
-  std::int64_t cycleLevel_;
+  const parser::CharBlock *source_;
+  std::int64_t level_;
   std::map<std::string, std::int64_t> constructNamesAndLevels_;
 };
 
@@ -657,8 +674,8 @@ std::int64_t OmpStructureChecker::GetOrdCollapseLevel(
 void OmpStructureChecker::CheckCycleConstraints(
     const parser::OpenMPLoopConstruct &x) {
   std::int64_t ordCollapseLevel{GetOrdCollapseLevel(x)};
-  OmpCycleChecker ompCycleChecker{context_, ordCollapseLevel};
-  parser::Walk(x, ompCycleChecker);
+  OmpCycleAndExitChecker checker{context_, ordCollapseLevel};
+  parser::Walk(x, checker);
 }
 
 void OmpStructureChecker::CheckDistLinear(

flang/test/Semantics/OpenMP/do08.f90

@@ -4,6 +4,8 @@
 
 program omp
   integer i, j, k
+  logical cond(10,10,10)
+  cond = .false.
 
   !ERROR: The value of the parameter in the COLLAPSE or ORDERED clause must not be larger than the number of nested loops following the construct.
   !$omp do  collapse(3)
@@ -135,4 +137,33 @@ program omp
   end do foo
   !$omp end do
 
+  !$omp do collapse(3)
+  loopk: do k=1,10
+    loopj: do j=1,10
+      loopi: do i=1,10
+        ifi : if (.true.) then
+          !ERROR: EXIT statement terminates associated loop of an OpenMP DO construct
+          if (cond(i,j,k)) exit
+          if (cond(i,j,k)) exit ifi
+          !ERROR: EXIT statement terminates associated loop of an OpenMP DO construct
+          if (cond(i,j,k)) exit loopi
+          !ERROR: EXIT statement terminates associated loop of an OpenMP DO construct
+          if (cond(i,j,k)) exit loopj
+        end if ifi
+      end do loopi
+    end do loopj
+  end do loopk
+  !$omp end do
+
+  !$omp do collapse(2)
+  loopk: do k=1,10
+    loopj: do j=1,10
+      do i=1,10
+      end do
+      !ERROR: EXIT statement terminates associated loop of an OpenMP DO construct
+      if (cond(i,j,k)) exit
+    end do loopj
+  end do loopk
+  !$omp end do
+
 end program omp