Reverse logic; Update the error message for the nested gang loops

Author: khaki3

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

@@ -293,7 +293,10 @@ void AccStructureChecker::CheckNotInSameOrSubLevelLoopConstruct() {
           bool invalid{false};
           if (parentClause == llvm::acc::Clause::ACCC_gang &&
               cl == llvm::acc::Clause::ACCC_gang) {
-            if (!IsInsideKernelsConstruct()) {
+            if (IsInsideKernelsConstruct()) {
+              context_.Say(GetContext().clauseSource,
+                  "Nested GANG loops are not allowed in the region of a KERNELS construct"_err_en_US);
+            } else {
               auto parentDim = getGangDimensionSize(parent);
               auto currentDim = getGangDimensionSize(GetContext());
               std::int64_t parentDimNum = 1, currentDimNum = 1;
@@ -317,8 +320,6 @@ void AccStructureChecker::CheckNotInSameOrSubLevelLoopConstruct() {
                     parentDimStr);
                 continue;
               }
-            } else {
-              invalid = true;
             }
           } else if (parentClause == llvm::acc::Clause::ACCC_worker &&
               (cl == llvm::acc::Clause::ACCC_gang ||

flang/test/Semantics/OpenACC/acc-loop.f90

@@ -340,10 +340,10 @@ program openacc_loop_validity
 
   !$acc kernels loop gang(dim:3)
   do i = 1, n
-    !ERROR: GANG clause is not allowed in the region of a loop with the GANG clause
+    !ERROR: Nested GANG loops are not allowed in the region of a KERNELS construct
     !$acc loop gang(dim:2)
     do j = 1, n
-      !ERROR: GANG clause is not allowed in the region of a loop with the GANG clause
+      !ERROR: Nested GANG loops are not allowed in the region of a KERNELS construct
       !$acc loop gang(dim:1) worker vector
       do k = 1, i
       end do