Split FindCommonBlock() into FindCB() and FindCommonBlockInScopes(). This resolves OpenMP regressions with COMMON. Still working on USE-association for COMMON blocks

Author: eugeneepshteyn

flang/include/flang/Semantics/scope.h

@@ -189,8 +189,21 @@ class Scope {
   mapType &commonBlocks() { return commonBlocks_; }
   const mapType &commonBlocks() const { return commonBlocks_; }
   Symbol &MakeCommonBlock(SourceName, SourceName location);
+
+  /// Find COMMON block in the current scope
+  Symbol *FindCB(const SourceName &name) const {
+    if (const auto it{commonBlocks_.find(name)}; it != commonBlocks_.end()) {
+      return &*it->second;
+    }
+    return nullptr;
+  }
+
+  /// Find COMMON block that is not USE-associated in the current scope
   Symbol *FindCommonBlock(const SourceName &) const;
 
+  /// Find COMMON block in current and surrounding scopes, follow USE associations
+  Symbol *FindCommonBlockInScopes(const SourceName &) const;
+
   /// Make a Symbol but don't add it to the scope.
   template <typename D>
   common::IfNoLvalue<Symbol &, D> MakeSymbol(

flang/lib/Semantics/resolve-directives.cpp

@@ -1698,7 +1698,7 @@ Symbol *AccAttributeVisitor::ResolveAccCommonBlockName(
   if (!name) {
     return nullptr;
   }
-  if (auto *cb{GetContext().scope.FindCommonBlock(name->source)}) {
+  if (auto *cb{GetContext().scope.FindCommonBlockInScopes(name->source)}) {
     name->symbol = cb;
     return cb;
   }

flang/lib/Semantics/scope.cpp

@@ -154,18 +154,33 @@ Symbol &Scope::MakeCommonBlock(SourceName name, SourceName location) {
     return symbol;
   }
 }
+
 Symbol *Scope::FindCommonBlock(const SourceName &name) const {
-  if (const auto it{commonBlocks_.find(name)}; it != commonBlocks_.end()) {
-    return &*it->second;
+  if (auto *cb{FindCB(name)}) {
+    // Ensure this COMMON block is not USE-associated
+    if (cb->has<UseDetails>()) {
+      cb = nullptr;
+    }
+    return cb;
+  }
+  return nullptr;
+}
+
+Symbol *Scope::FindCommonBlockInScopes(const SourceName &name) const {
+  if (auto *cb{FindCB(name)}) {
+    return &cb->GetUltimate();
   } else if (IsSubmodule()) {
-    const Scope *parent{
-        symbol_ ? symbol_->get<ModuleDetails>().parent() : nullptr};
-    return parent ? parent->FindCommonBlock(name) : nullptr;
-  } else if (!IsTopLevel()) {
-    return parent_ ? parent_->FindCommonBlock(name) : nullptr;
-  } else {
-    return nullptr;
+    if (const Scope *parent{symbol_ ? symbol_->get<ModuleDetails>().parent() : nullptr}) {
+      if (auto *cb{parent->FindCommonBlockInScopes(name)}) {
+        return &cb->GetUltimate();
+      }
+    }
+  } else if (!IsTopLevel() && parent_) {
+    if (auto *cb{parent_->FindCommonBlockInScopes(name)}) {
+      return &cb->GetUltimate();
+    }
   }
+  return nullptr;
 }
 
 Scope *Scope::FindSubmodule(const SourceName &name) const {