r266160 - [modules] Refactor handling of cases where we write an offset to a prior record into the bitstream and simplify a little, in preparation for doing this in more cases.

Nico Weber via cfe-commits cfe-commits at lists.llvm.org
Wed Apr 13 19:24:44 PDT 2016


On Tue, Apr 12, 2016 at 10:12 PM, Richard Smith via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> Author: rsmith
> Date: Tue Apr 12 21:12:03 2016
> New Revision: 266160
>
> URL: http://llvm.org/viewvc/llvm-project?rev=266160&view=rev
> Log:
> [modules] Refactor handling of cases where we write an offset to a prior
> record into the bitstream and simplify a little, in preparation for doing
> this in more cases.
>
> Modified:
>     cfe/trunk/include/clang/Serialization/ASTWriter.h
>     cfe/trunk/lib/Serialization/ASTWriter.cpp
>     cfe/trunk/lib/Serialization/ASTWriterDecl.cpp
>
> Modified: cfe/trunk/include/clang/Serialization/ASTWriter.h
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Serialization/ASTWriter.h?rev=266160&r1=266159&r2=266160&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/Serialization/ASTWriter.h (original)
> +++ cfe/trunk/include/clang/Serialization/ASTWriter.h Tue Apr 12 21:12:03
> 2016
> @@ -787,11 +787,29 @@ class ASTRecordWriter {
>    /// declaration or type.
>    SmallVector<Stmt *, 16> StmtsToEmit;
>
> +  static constexpr int MaxOffsetIndices = 4;
> +  /// \brief Indices of record elements that describe offsets within the
> +  /// bitcode. These will be converted to offsets relative to the current
> +  /// record when emitted.
> +  unsigned OffsetIndices[MaxOffsetIndices];
> +  unsigned NumOffsetIndices = 0;
> +
>    /// \brief Flush all of the statements and expressions that have
>    /// been added to the queue via AddStmt().
>    void FlushStmts();
>    void FlushSubStmts();
>
> +  void PrepareToEmit(uint64_t MyOffset) {
> +    // Convert offsets into relative form.
> +    for (unsigned I = 0; I != NumOffsetIndices; ++I) {
> +      auto &StoredOffset = (*Record)[OffsetIndices[I]];
> +      assert(StoredOffset < MyOffset && "invalid offset");
> +      if (StoredOffset)
> +        StoredOffset = MyOffset - StoredOffset;
> +    }
> +    NumOffsetIndices = 0;
> +  }
> +
>  public:
>    /// Construct a ASTRecordWriter that uses the default encoding scheme.
>    ASTRecordWriter(ASTWriter &Writer, ASTWriter::RecordDataImpl &Record)
> @@ -802,6 +820,10 @@ public:
>    ASTRecordWriter(ASTRecordWriter &Parent, ASTWriter::RecordDataImpl
> &Record)
>        : Writer(Parent.Writer), Record(&Record) {}
>
> +  /// Copying an ASTRecordWriter is almost certainly a bug.
> +  ASTRecordWriter(const ASTRecordWriter&) = delete;
> +  void operator=(const ASTRecordWriter&) = delete;
> +
>    /// \brief Extract the underlying record storage.
>    ASTWriter::RecordDataImpl &getRecordData() const { return *Record; }
>
> @@ -822,6 +844,7 @@ public:
>    // FIXME: Allow record producers to suggest Abbrevs.
>    uint64_t Emit(unsigned Code, unsigned Abbrev = 0) {
>      uint64_t Offset = Writer->Stream.GetCurrentBitNo();
> +    PrepareToEmit(Offset);
>      Writer->Stream.EmitRecord(Code, *Record, Abbrev);
>      FlushStmts();
>      return Offset;
> @@ -830,10 +853,19 @@ public:
>    /// \brief Emit the record to the stream, preceded by its substatements.
>    uint64_t EmitStmt(unsigned Code, unsigned Abbrev = 0) {
>      FlushSubStmts();
> +    PrepareToEmit(Writer->Stream.GetCurrentBitNo());
>      Writer->Stream.EmitRecord(Code, *Record, Abbrev);
>      return Writer->Stream.GetCurrentBitNo();
>    }
>
> +  /// \brief Add a bit offset into the record. This will be converted
> into an
> +  /// offset relative to the current record when emitted.
> +  void AddOffset(uint64_t BitOffset) {
> +    assert(NumOffsetIndices != MaxOffsetIndices && "too many offset
> indices");
>

This assert is firing when building chrome with clang-cl on Windows:
https://build.chromium.org/p/chromium.fyi/builders/ClangToTWin%28dbg%29/builds/5340/steps/compile/logs/stdio


> +    OffsetIndices[NumOffsetIndices++] = Record->size();
> +    Record->push_back(BitOffset);
> +  }
> +
>    /// \brief Add the given statement or expression to the queue of
>    /// statements to emit.
>    ///
>
> Modified: cfe/trunk/lib/Serialization/ASTWriter.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTWriter.cpp?rev=266160&r1=266159&r2=266160&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Serialization/ASTWriter.cpp (original)
> +++ cfe/trunk/lib/Serialization/ASTWriter.cpp Tue Apr 12 21:12:03 2016
> @@ -4694,6 +4694,7 @@ void ASTWriter::WriteDeclUpdatesBlocks(R
>          auto *RD = cast<CXXRecordDecl>(D);
>          UpdatedDeclContexts.insert(RD->getPrimaryContext());
>          Record.AddCXXDefinitionData(RD);
> +        // FIXME: Use AddOffset here.
>          Record.push_back(WriteDeclContextLexicalBlock(
>              *Context, const_cast<CXXRecordDecl *>(RD)));
>
>
> Modified: cfe/trunk/lib/Serialization/ASTWriterDecl.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTWriterDecl.cpp?rev=266160&r1=266159&r2=266160&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Serialization/ASTWriterDecl.cpp (original)
> +++ cfe/trunk/lib/Serialization/ASTWriterDecl.cpp Tue Apr 12 21:12:03 2016
> @@ -125,8 +125,7 @@ namespace clang {
>      void VisitCapturedDecl(CapturedDecl *D);
>      void VisitEmptyDecl(EmptyDecl *D);
>
> -    void VisitDeclContext(DeclContext *DC, uint64_t LexicalOffset,
> -                          uint64_t VisibleOffset);
> +    void VisitDeclContext(DeclContext *DC);
>      template <typename T> void VisitRedeclarable(Redeclarable<T> *D);
>
>
> @@ -149,12 +148,6 @@ namespace clang {
>      void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
>      void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
>
> -    void AddLocalOffset(uint64_t LocalOffset) {
> -      uint64_t Offset = Writer.Stream.GetCurrentBitNo();
> -      assert(LocalOffset < Offset && "invalid offset");
> -      Record.push_back(LocalOffset ? Offset - LocalOffset : 0);
> -    }
> -
>      /// Add an Objective-C type parameter list to the given record.
>      void AddObjCTypeParamList(ObjCTypeParamList *typeParams) {
>        // Empty type parameter list.
> @@ -284,6 +277,12 @@ void ASTDeclWriter::Visit(Decl *D) {
>      if (FD->doesThisDeclarationHaveABody())
>        Record.AddFunctionDefinition(FD);
>    }
> +
> +  // If this declaration is also a DeclContext, write blocks for the
> +  // declarations that lexically stored inside its context and those
> +  // declarations that are visible from its context.
> +  if (DeclContext *DC = dyn_cast<DeclContext>(D))
> +    VisitDeclContext(DC);
>  }
>
>  void ASTDeclWriter::VisitDecl(Decl *D) {
> @@ -1553,10 +1552,9 @@ void ASTDeclWriter::VisitStaticAssertDec
>  /// that there are no declarations visible from this context. Note
>  /// that this value will not be emitted for non-primary declaration
>  /// contexts.
> -void ASTDeclWriter::VisitDeclContext(DeclContext *DC, uint64_t
> LexicalOffset,
> -                                     uint64_t VisibleOffset) {
> -  AddLocalOffset(LexicalOffset);
> -  AddLocalOffset(VisibleOffset);
> +void ASTDeclWriter::VisitDeclContext(DeclContext *DC) {
> +  Record.AddOffset(Writer.WriteDeclContextLexicalBlock(Context, DC));
> +  Record.AddOffset(Writer.WriteDeclContextVisibleBlock(Context, DC));
>  }
>
>  const Decl *ASTWriter::getFirstLocalDecl(const Decl *D) {
> @@ -1624,9 +1622,8 @@ void ASTDeclWriter::VisitRedeclarable(Re
>        // the declaration itself.
>        if (LocalRedecls.empty())
>          Record.push_back(0);
> -      else {
> -        AddLocalOffset(LocalRedeclWriter.Emit(LOCAL_REDECLARATIONS));
> -      }
> +      else
> +        Record.AddOffset(LocalRedeclWriter.Emit(LOCAL_REDECLARATIONS));
>      } else {
>        Record.push_back(0);
>        Record.AddDeclRef(FirstLocal);
> @@ -2148,26 +2145,12 @@ void ASTWriter::WriteDecl(ASTContext &Co
>    ID = IDR;
>
>    assert(ID >= FirstDeclID && "invalid decl ID");
> -
> -  // If this declaration is also a DeclContext, write blocks for the
> -  // declarations that lexically stored inside its context and those
> -  // declarations that are visible from its context. These blocks
> -  // are written before the declaration itself so that we can put
> -  // their offsets into the record for the declaration.
> -  uint64_t LexicalOffset = 0;
> -  uint64_t VisibleOffset = 0;
> -  DeclContext *DC = dyn_cast<DeclContext>(D);
> -  if (DC) {
> -    LexicalOffset = WriteDeclContextLexicalBlock(Context, DC);
> -    VisibleOffset = WriteDeclContextVisibleBlock(Context, DC);
> -  }
>
>    RecordData Record;
>    ASTDeclWriter W(*this, Context, Record);
>
>    // Build a record for this declaration
>    W.Visit(D);
> -  if (DC) W.VisitDeclContext(DC, LexicalOffset, VisibleOffset);
>
>    // Emit this declaration to the bitstream.
>    uint64_t Offset = W.Emit(D);
>
>
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