[demangler] Adjust unqualified name parsing

[urnathan]

Summary

The unqualified name grammar includes <ctor-dtor-name>, but we handle that specially in parseNestedName. This is a little awkward. We can pass in the current scope and have parseUnqualifiedName deal with cdtors too. That also allows a couple of other simplifications:

1. parseUnqualifiedName can also build up the NestedName, when the provided scope is non-null. Which means ...

2. parseUnscopedName can pass a "std" scope in (and tailcall).

3. ... and also parseNestedName need not construct the nestedname itself.

4. also parseNestedName's detection of a cdtor-name doesn't have to rule out a decomposition name anymore.

This change also makes adding module demangling more straight-forwards, btw.

[ChuanqiXu]

libcxxabi/src/demangle/ItaniumDemangle.h

2668

The original version would try to consume 'L' all the way. Is this a intentional difference?

[urnathan]

libcxxabi/src/demangle/ItaniumDemangle.h

2668

Once we've reached an error condition (failing to create Std node), it doesn't matter what we leave unconsumed.

libcxxabi/src/demangle/ItaniumDemangle.h

bool resolveForwardTemplateRefs(NameState &State) {
     ForwardTemplateRefs.dropBack(State.ForwardTemplateRefsBegin);
     return false;
   }
 
   /// Parse the <name> production>
   Node *parseName(NameState *State = nullptr);
   Node *parseLocalName(NameState *State);
   Node *parseOperatorName(NameState *State);
-  Node *parseUnqualifiedName(NameState *State);
+  Node *parseUnqualifiedName(NameState *State, Node *Scope);
   Node *parseUnnamedTypeName(NameState *State);
   Node *parseSourceName(NameState *State);
   Node *parseUnscopedName(NameState *State);
   Node *parseNestedName(NameState *State);
   Node *parseCtorDtorName(Node *&SoFar, NameState *State);
 
   Node *parseAbiTags(Node *N);
 

 }
 
 // <unscoped-name> ::= [L]* <unqualified-name>
 //                 ::= St [L]* <unqualified-name>   # ::std::
 // [*] extension
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseUnscopedName(NameState *State) {
-  bool IsStd = consumeIf("St");
-  consumeIf('L');
-
-  Node *Result = getDerived().parseUnqualifiedName(State);
-  if (Result == nullptr)
-    return nullptr;
-  if (IsStd) {
-    if (auto *Std = make<NameType>("std"))
-      Result = make<NestedName>(Std, Result);
-    else
+  Node *Std = nullptr;
+  if (consumeIf("St")) {
+    Std = make<NameType>("std");
+    if (Std == nullptr)
       return nullptr;
   }
+  consumeIf('L');
 
-  return Result;
+  return getDerived().parseUnqualifiedName(State, Std);
 }
 
 // <unqualified-name> ::= <operator-name> [abi-tags]
-//                    ::= <ctor-dtor-name>
-//                    ::= <source-name>
-//                    ::= <unnamed-type-name>
+//                    ::= <ctor-dtor-name> [<abi-tags>]
+//                    ::= <source-name> [<abi-tags>]
+//                    ::= <unnamed-type-name> [<abi-tags>]
 //                    ::= DC <source-name>+ E      # structured binding declaration
 template <typename Derived, typename Alloc>
 Node *
-AbstractManglingParser<Derived, Alloc>::parseUnqualifiedName(NameState *State) {
-  // <ctor-dtor-name>s are special-cased in parseNestedName().
+AbstractManglingParser<Derived, Alloc>::parseUnqualifiedName(NameState *State,
+                                                             Node *Scope) {
   Node *Result;
   if (look() == 'U')
     Result = getDerived().parseUnnamedTypeName(State);
   else if (look() >= '1' && look() <= '9')
     Result = getDerived().parseSourceName(State);
   else if (consumeIf("DC")) {
+    // Structured binding
     size_t BindingsBegin = Names.size();
     do {
       Node *Binding = getDerived().parseSourceName(State);
       if (Binding == nullptr)
         return nullptr;
       Names.push_back(Binding);
     } while (!consumeIf('E'));
     Result = make<StructuredBindingName>(popTrailingNodeArray(BindingsBegin));
-  } else
+  } else if (look() == 'C' || look() == 'D') {
+    // A <ctor-dtor-name>.
+    if (Scope == nullptr)
+      return nullptr;
+    Result = getDerived().parseCtorDtorName(Scope, State);
+  } else {
     Result = getDerived().parseOperatorName(State);
+  }
   if (Result != nullptr)
     Result = getDerived().parseAbiTags(Result);
+  if (Result != nullptr && Scope != nullptr)
+    Result = make<NestedName>(Scope, Result);
   return Result;
 }
 
 // <unnamed-type-name> ::= Ut [<nonnegative number>] _
 //                     ::= <closure-type-name>
 //
 // <closure-type-name> ::= Ul <lambda-sig> E [ <nonnegative number> ] _
 //
if (look() == 'T') {
         SoFar = make<NameType>("std");
       } else {
         SoFar = getDerived().parseSubstitution();
       }
       if (SoFar == nullptr)
         return nullptr;
       continue; // Do not push a new substitution.
     } else {
-      Node *N = nullptr;
-      if (look() == 'C' || (look() == 'D' && look(1) != 'C')) {
-        // An <unqualified-name> that's actually a <ctor-dtor-name>.
-        if (SoFar == nullptr)
-          return nullptr;
-        N = getDerived().parseCtorDtorName(SoFar, State);
-        if (N != nullptr)
-          N = getDerived().parseAbiTags(N);
-      } else {
-        //          ::= <prefix> <unqualified-name>
-        N = getDerived().parseUnqualifiedName(State);
-      }
-      if (N == nullptr)
-        return nullptr;
-      if (SoFar)
-        SoFar = make<NestedName>(SoFar, N);
-      else
-        SoFar = N;
+      //          ::= [<prefix>] <unqualified-name>
+      SoFar = getDerived().parseUnqualifiedName(State, SoFar);
     }
     if (SoFar == nullptr)
       return nullptr;
     Subs.push_back(SoFar);
   }
 
   if (SoFar == nullptr || Subs.empty())
     return nullptr;

llvm/include/llvm/Demangle/ItaniumDemangle.h

bool resolveForwardTemplateRefs(NameState &State) {
     ForwardTemplateRefs.dropBack(State.ForwardTemplateRefsBegin);
     return false;
   }
 
   /// Parse the <name> production>
   Node *parseName(NameState *State = nullptr);
   Node *parseLocalName(NameState *State);
   Node *parseOperatorName(NameState *State);
-  Node *parseUnqualifiedName(NameState *State);
+  Node *parseUnqualifiedName(NameState *State, Node *Scope);
   Node *parseUnnamedTypeName(NameState *State);
   Node *parseSourceName(NameState *State);
   Node *parseUnscopedName(NameState *State);
   Node *parseNestedName(NameState *State);
   Node *parseCtorDtorName(Node *&SoFar, NameState *State);
 
   Node *parseAbiTags(Node *N);
 

 }
 
 // <unscoped-name> ::= [L]* <unqualified-name>
 //                 ::= St [L]* <unqualified-name>   # ::std::
 // [*] extension
 template <typename Derived, typename Alloc>
 Node *
 AbstractManglingParser<Derived, Alloc>::parseUnscopedName(NameState *State) {
-  bool IsStd = consumeIf("St");
-  consumeIf('L');
-
-  Node *Result = getDerived().parseUnqualifiedName(State);
-  if (Result == nullptr)
-    return nullptr;
-  if (IsStd) {
-    if (auto *Std = make<NameType>("std"))
-      Result = make<NestedName>(Std, Result);
-    else
+  Node *Std = nullptr;
+  if (consumeIf("St")) {
+    Std = make<NameType>("std");
+    if (Std == nullptr)
       return nullptr;
   }
+  consumeIf('L');
 
-  return Result;
+  return getDerived().parseUnqualifiedName(State, Std);
 }
 
 // <unqualified-name> ::= <operator-name> [abi-tags]
-//                    ::= <ctor-dtor-name>
-//                    ::= <source-name>
-//                    ::= <unnamed-type-name>
+//                    ::= <ctor-dtor-name> [<abi-tags>]
+//                    ::= <source-name> [<abi-tags>]
+//                    ::= <unnamed-type-name> [<abi-tags>]
 //                    ::= DC <source-name>+ E      # structured binding declaration
 template <typename Derived, typename Alloc>
 Node *
-AbstractManglingParser<Derived, Alloc>::parseUnqualifiedName(NameState *State) {
-  // <ctor-dtor-name>s are special-cased in parseNestedName().
+AbstractManglingParser<Derived, Alloc>::parseUnqualifiedName(NameState *State,
+                                                             Node *Scope) {
   Node *Result;
   if (look() == 'U')
     Result = getDerived().parseUnnamedTypeName(State);
   else if (look() >= '1' && look() <= '9')
     Result = getDerived().parseSourceName(State);
   else if (consumeIf("DC")) {
+    // Structured binding
     size_t BindingsBegin = Names.size();
     do {
       Node *Binding = getDerived().parseSourceName(State);
       if (Binding == nullptr)
         return nullptr;
       Names.push_back(Binding);
     } while (!consumeIf('E'));
     Result = make<StructuredBindingName>(popTrailingNodeArray(BindingsBegin));
-  } else
+  } else if (look() == 'C' || look() == 'D') {
+    // A <ctor-dtor-name>.
+    if (Scope == nullptr)
+      return nullptr;
+    Result = getDerived().parseCtorDtorName(Scope, State);
+  } else {
     Result = getDerived().parseOperatorName(State);
+  }
   if (Result != nullptr)
     Result = getDerived().parseAbiTags(Result);
+  if (Result != nullptr && Scope != nullptr)
+    Result = make<NestedName>(Scope, Result);
   return Result;
 }
 
 // <unnamed-type-name> ::= Ut [<nonnegative number>] _
 //                     ::= <closure-type-name>
 //
 // <closure-type-name> ::= Ul <lambda-sig> E [ <nonnegative number> ] _
 //
if (look() == 'T') {
         SoFar = make<NameType>("std");
       } else {
         SoFar = getDerived().parseSubstitution();
       }
       if (SoFar == nullptr)
         return nullptr;
       continue; // Do not push a new substitution.
     } else {
-      Node *N = nullptr;
-      if (look() == 'C' || (look() == 'D' && look(1) != 'C')) {
-        // An <unqualified-name> that's actually a <ctor-dtor-name>.
-        if (SoFar == nullptr)
-          return nullptr;
-        N = getDerived().parseCtorDtorName(SoFar, State);
-        if (N != nullptr)
-          N = getDerived().parseAbiTags(N);
-      } else {
-        //          ::= <prefix> <unqualified-name>
-        N = getDerived().parseUnqualifiedName(State);
-      }
-      if (N == nullptr)
-        return nullptr;
-      if (SoFar)
-        SoFar = make<NestedName>(SoFar, N);
-      else
-        SoFar = N;
+      //          ::= [<prefix>] <unqualified-name>
+      SoFar = getDerived().parseUnqualifiedName(State, SoFar);
     }
     if (SoFar == nullptr)
       return nullptr;
     Subs.push_back(SoFar);
   }
 
   if (SoFar == nullptr || Subs.empty())
     return nullptr;