r231901 - [modules] Avoid accidentally completing the redeclaration chain when updating

[Vassil Vassilev]

This made me think, is there a way to automatically find out redundant 
deserializations? Eg. switch to text mode, build dependency graph and 
compare against the dependency graph in -fmodules mode. Or even a more 
brute force: store the states of the key objects (AST, identifiers, 
lookups, directives ...) and compare?
Vassil
On 11/03/15 02:44, Richard Smith wrote:
> Author: rsmith
> Date: Tue Mar 10 20:44:51 2015
> New Revision: 231901
>
> URL: http://llvm.org/viewvc/llvm-project?rev=231901&view=rev
> Log:
> [modules] Avoid accidentally completing the redeclaration chain when updating
> all the existing declarations of a record-like entity with a pointer to its
> definition.
>
> Modified:
>      cfe/trunk/include/clang/Serialization/ASTReader.h
>      cfe/trunk/lib/Serialization/ASTReader.cpp
>      cfe/trunk/lib/Serialization/ASTReaderDecl.cpp
>
> Modified: cfe/trunk/include/clang/Serialization/ASTReader.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Serialization/ASTReader.h?rev=231901&r1=231900&r2=231901&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Serialization/ASTReader.h (original)
> +++ cfe/trunk/include/clang/Serialization/ASTReader.h Tue Mar 10 20:44:51 2015
> @@ -1159,6 +1159,12 @@ private:
>     void LoadedDecl(unsigned Index, Decl *D);
>     Decl *ReadDeclRecord(serialization::DeclID ID);
>     void markIncompleteDeclChain(Decl *Canon);
> +
> +  /// \brief Returns the most recent declaration of a declaration (which must be
> +  /// of a redeclarable kind) that is either local or has already been loaded
> +  /// merged into its redecl chain.
> +  Decl *getMostRecentExistingDecl(Decl *D);
> +
>     RecordLocation DeclCursorForID(serialization::DeclID ID,
>                                    unsigned &RawLocation);
>     void loadDeclUpdateRecords(serialization::DeclID ID, Decl *D);
>
> Modified: cfe/trunk/lib/Serialization/ASTReader.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReader.cpp?rev=231901&r1=231900&r2=231901&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Serialization/ASTReader.cpp (original)
> +++ cfe/trunk/lib/Serialization/ASTReader.cpp Tue Mar 10 20:44:51 2015
> @@ -8369,10 +8369,12 @@ void ASTReader::finishPendingActions() {
>           // Make sure that the TagType points at the definition.
>           const_cast<TagType*>(TagT)->decl = TD;
>         }
> -
> +
>         if (auto RD = dyn_cast<CXXRecordDecl>(D)) {
> -        for (auto R : RD->redecls()) {
> -          assert((R == D) == R->isThisDeclarationADefinition() &&
> +        for (auto *R = getMostRecentExistingDecl(RD); R;
> +             R = R->getPreviousDecl()) {
> +          assert((R == D) ==
> +                     cast<CXXRecordDecl>(R)->isThisDeclarationADefinition() &&
>                    "declaration thinks it's the definition but it isn't");
>             cast<CXXRecordDecl>(R)->DefinitionData = RD->DefinitionData;
>           }
> @@ -8380,34 +8382,36 @@ void ASTReader::finishPendingActions() {
>   
>         continue;
>       }
> -
> +
>       if (auto ID = dyn_cast<ObjCInterfaceDecl>(D)) {
>         // Make sure that the ObjCInterfaceType points at the definition.
>         const_cast<ObjCInterfaceType *>(cast<ObjCInterfaceType>(ID->TypeForDecl))
>           ->Decl = ID;
> -
> -      for (auto R : ID->redecls())
> -        R->Data = ID->Data;
> -
> +
> +      for (auto *R = getMostRecentExistingDecl(ID); R; R = R->getPreviousDecl())
> +        cast<ObjCInterfaceDecl>(R)->Data = ID->Data;
> +
>         continue;
>       }
> -
> +
>       if (auto PD = dyn_cast<ObjCProtocolDecl>(D)) {
> -      for (auto R : PD->redecls())
> -        R->Data = PD->Data;
> -
> +      for (auto *R = getMostRecentExistingDecl(PD); R; R = R->getPreviousDecl())
> +        cast<ObjCProtocolDecl>(R)->Data = PD->Data;
> +
>         continue;
>       }
> -
> +
>       auto RTD = cast<RedeclarableTemplateDecl>(D)->getCanonicalDecl();
> -    for (auto R : RTD->redecls())
> -      R->Common = RTD->Common;
> +    for (auto *R = getMostRecentExistingDecl(RTD); R; R = R->getPreviousDecl())
> +      cast<RedeclarableTemplateDecl>(R)->Common = RTD->Common;
>     }
>     PendingDefinitions.clear();
>   
>     // Load the bodies of any functions or methods we've encountered. We do
>     // this now (delayed) so that we can be sure that the declaration chains
>     // have been fully wired up.
> +  // FIXME: There seems to be no point in delaying this, it does not depend
> +  // on the redecl chains having been wired up.
>     for (PendingBodiesMap::iterator PB = PendingBodies.begin(),
>                                  PBEnd = PendingBodies.end();
>          PB != PBEnd; ++PB) {
>
> Modified: cfe/trunk/lib/Serialization/ASTReaderDecl.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReaderDecl.cpp?rev=231901&r1=231900&r2=231901&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Serialization/ASTReaderDecl.cpp (original)
> +++ cfe/trunk/lib/Serialization/ASTReaderDecl.cpp Tue Mar 10 20:44:51 2015
> @@ -2799,6 +2799,10 @@ Decl *ASTDeclReader::getMostRecentDecl(D
>     llvm_unreachable("unknown decl kind");
>   }
>   
> +Decl *ASTReader::getMostRecentExistingDecl(Decl *D) {
> +  return ASTDeclReader::getMostRecentDecl(D->getCanonicalDecl());
> +}
> +
>   template<typename DeclT>
>   void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
>                                              Redeclarable<DeclT> *D,
>
>
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