[flang-commits] [flang] [flang][openacc] Fix DEFAULT(NONE) errors for array sections (PR #204248)

[Andre Kuhlenschmidt via flang-commits]

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@@ -1905,24 +1905,33 @@ void AccAttributeVisitor::ResolveAccObject(
   common::visit(
       common::visitors{
           [&](const parser::Designator &designator) {
-            if (const auto *name{
-                    parser::GetDesignatorNameIfDataRef(designator)}) {
-              if (auto *symbol{ResolveAcc(*name, accFlag, currScope())}) {
-                AddToContextObjectWithDSA(*symbol, accFlag);
-                if (dataSharingAttributeFlags.test(accFlag)) {
-                  CheckMultipleAppearances(*name, *symbol, accFlag, &accObject);
-                }
-              }
-            } else {
-              // Array sections to be changed to substrings as needed
+            const bool isDataRef{
+                parser::GetDesignatorNameIfDataRef(designator) != nullptr};
+            if (!isDataRef) {
+              // Subscripted designator: evaluate subscripts and detect
+              // the substring case that is disallowed in OpenACC clauses.
               if (AnalyzeExpr(context_, designator)) {
                 if (std::holds_alternative<parser::Substring>(designator.u)) {
                   context_.Say(designator.source,
                       "Substrings are not allowed on OpenACC "
                       "directives or clauses"_err_en_US);
+                  return;
                 }
               }
-              // other checks, more TBD
+            }
+            // GetFirstName extracts the base symbol from both bare data
+            // references and array sections, unifying DSA registration so
+            // that DEFAULT(NONE) checking does not spuriously flag variables
+            // that are explicitly listed in a data clause as array sections.
+            // TODO: Multiple array sections of the same array with different
+            // data sharing attributes is not currently supported.
+            const parser::Name &baseName{parser::GetFirstName(designator)};
----------------
akuhlens wrote:

After extensive testing. GetLastName isn't good enough. We will have to generalize the dsa analysis to keep track of paths into subobjects to get accuracy. I have made checking more lenient for array sections since the backend seems to be compiling those (I will double check), but outright reject component references in declaration clauses for now since code lowering will fail with a todo there anyway.

https://github.com/llvm/llvm-project/pull/204248