[flang-commits] [flang] [flang][OpenACC] Relax COMMON block usage restriction in OpenACC directives (PR #162659)

[Eugene Epshteyn via flang-commits]

================
@@ -1695,17 +1695,23 @@ void AccAttributeVisitor::Post(const parser::Name &name) {
 
 Symbol *AccAttributeVisitor::ResolveAccCommonBlockName(
     const parser::Name *name) {
-  if (auto *prev{name
-              ? GetContext().scope.parent().FindCommonBlock(name->source)
-              : nullptr}) {
-    name->symbol = prev;
-    return prev;
-  }
-  // Check if the Common Block is declared in the current scope
-  if (auto *commonBlockSymbol{
-          name ? GetContext().scope.FindCommonBlock(name->source) : nullptr}) {
-    name->symbol = commonBlockSymbol;
-    return commonBlockSymbol;
+  if (!name) {
+    return nullptr;
+  }
+  // Check the local and surrounding scopes first
+  if (auto *cb{GetProgramUnitOrBlockConstructContaining(GetContext().scope)
+              .FindCommonBlock(name->source)}) {
+    name->symbol = cb;
+    return cb;
+  }
+  // Look for COMMON block in the modules
----------------
eugeneepshteyn wrote:

It would have been very convenient to have a USE-associated common block available, but I don't see one created. With this program
```
module acc_decl
  implicit none
  integer a
  common /a_common/ a
!$acc declare create (/a_common/)
  data a/42/
end module acc_decl

program acc_decl_test
  use acc_decl
  implicit none

  a = 1
!$acc update device (/a_common/)
  a = 2
end program
```
... and `-fdebug-dump-symbols` I only see
```
  MainProgram scope: ACC_DECL_TEST size=0 alignment=1 sourceRange=72 bytes
    a (InDataStmt, InCommonBlock): Use from a in acc_decl
```
Perhaps this is the problem? Perhaps we should be creating USE-associated symbol from its use in `!$acc update device (/a_common/)`?

https://github.com/llvm/llvm-project/pull/162659