[clang][modules][deps] Create more efficient API for visitation of `M…

…oduleFile` inputs

The current `ASTReader::visitInputFiles()` function calls into `FileManager` to create `FileEntryRef` objects. This ends up being fairly costly in `clang-scan-deps`, where we mostly only care about file paths.

This patch introduces new `ASTReader` API that gives clients access to just the serialized paths. Since the scanner needs both the as-requested path and the on-disk one (and doesn't want to transform the former into the latter via `FileManager`), this patch starts serializing both of them into the PCM file if they differ.

This increases the size of scanning PCMs by 0.1% and speeds up scanning by 5%.

Reviewed By: benlangmuir, vsapsai

Differential Revision: https://reviews.llvm.org/D157066

clang/include/clang/Serialization/ASTBitCodes.h

@@ -41,7 +41,7 @@ namespace serialization {
 /// Version 4 of AST files also requires that the version control branch and
 /// revision match exactly, since there is no backward compatibility of
 /// AST files at this time.
-const unsigned VERSION_MAJOR = 27;
+const unsigned VERSION_MAJOR = 28;
 
 /// AST file minor version number supported by this version of
 /// Clang.

clang/include/clang/Serialization/ASTReader.h

@@ -2373,6 +2373,13 @@ class ASTReader
   /// Loads comments ranges.
   void ReadComments() override;
 
+  /// Visit all the input file infos of the given module file.
+  void visitInputFileInfos(
+      serialization::ModuleFile &MF, bool IncludeSystem,
+      llvm::function_ref<void(const serialization::InputFileInfo &IFI,
+                              bool IsSystem)>
+          Visitor);
+
   /// Visit all the input files of the given module file.
   void visitInputFiles(serialization::ModuleFile &MF,
                        bool IncludeSystem, bool Complain,

clang/include/clang/Serialization/ModuleFile.h

@@ -61,13 +61,15 @@ enum ModuleKind {
 
 /// The input file info that has been loaded from an AST file.
 struct InputFileInfo {
+  std::string FilenameAsRequested;
   std::string Filename;
   uint64_t ContentHash;
   off_t StoredSize;
   time_t StoredTime;
   bool Overridden;
   bool Transient;
-  bool TopLevelModuleMap;
+  bool TopLevel;
+  bool ModuleMap;
 };
 
 /// The input file that has been loaded from this AST file, along with

clang/lib/Serialization/ASTReader.cpp

@@ -2342,9 +2342,22 @@ InputFileInfo ASTReader::getInputFileInfo(ModuleFile &F, unsigned ID) {
   R.StoredTime = static_cast<time_t>(Record[2]);
   R.Overridden = static_cast<bool>(Record[3]);
   R.Transient = static_cast<bool>(Record[4]);
-  R.TopLevelModuleMap = static_cast<bool>(Record[5]);
-  R.Filename = std::string(Blob);
-  ResolveImportedPath(F, R.Filename);
+  R.TopLevel = static_cast<bool>(Record[5]);
+  R.ModuleMap = static_cast<bool>(Record[6]);
+  std::tie(R.FilenameAsRequested, R.Filename) = [&]() {
+    uint16_t AsRequestedLength = Record[7];
+
+    std::string NameAsRequested = Blob.substr(0, AsRequestedLength).str();
+    std::string Name = Blob.substr(AsRequestedLength).str();
+
+    ResolveImportedPath(F, NameAsRequested);
+    ResolveImportedPath(F, Name);
+
+    if (Name.empty())
+      Name = NameAsRequested;
+
+    return std::make_pair(std::move(NameAsRequested), std::move(Name));
+  }();
 
   Expected<llvm::BitstreamEntry> MaybeEntry = Cursor.advance();
   if (!MaybeEntry) // FIXME this drops errors on the floor.
@@ -2395,7 +2408,7 @@ InputFile ASTReader::getInputFile(ModuleFile &F, unsigned ID, bool Complain) {
   time_t StoredTime = FI.StoredTime;
   bool Overridden = FI.Overridden;
   bool Transient = FI.Transient;
-  StringRef Filename = FI.Filename;
+  StringRef Filename = FI.FilenameAsRequested;
   uint64_t StoredContentHash = FI.ContentHash;
 
   // For standard C++ modules, we don't need to check the inputs.
@@ -2742,9 +2755,9 @@ ASTReader::ReadControlBlock(ModuleFile &F,
         for (unsigned I = 0; I < N; ++I) {
           bool IsSystem = I >= NumUserInputs;
           InputFileInfo FI = getInputFileInfo(F, I + 1);
-          Listener->visitInputFile(FI.Filename, IsSystem, FI.Overridden,
-                                   F.Kind == MK_ExplicitModule ||
-                                   F.Kind == MK_PrebuiltModule);
+          Listener->visitInputFile(
+              FI.FilenameAsRequested, IsSystem, FI.Overridden,
+              F.Kind == MK_ExplicitModule || F.Kind == MK_PrebuiltModule);
         }
       }
 
@@ -9307,6 +9320,22 @@ void ASTReader::ReadComments() {
   }
 }
 
+void ASTReader::visitInputFileInfos(
+    serialization::ModuleFile &MF, bool IncludeSystem,
+    llvm::function_ref<void(const serialization::InputFileInfo &IFI,
+                            bool IsSystem)>
+        Visitor) {
+  unsigned NumUserInputs = MF.NumUserInputFiles;
+  unsigned NumInputs = MF.InputFilesLoaded.size();
+  assert(NumUserInputs <= NumInputs);
+  unsigned N = IncludeSystem ? NumInputs : NumUserInputs;
+  for (unsigned I = 0; I < N; ++I) {
+    bool IsSystem = I >= NumUserInputs;
+    InputFileInfo IFI = getInputFileInfo(MF, I+1);
+    Visitor(IFI, IsSystem);
+  }
+}
+
 void ASTReader::visitInputFiles(serialization::ModuleFile &MF,
                                 bool IncludeSystem, bool Complain,
                     llvm::function_ref<void(const serialization::InputFile &IF,
@@ -9328,7 +9357,7 @@ void ASTReader::visitTopLevelModuleMaps(
   unsigned NumInputs = MF.InputFilesLoaded.size();
   for (unsigned I = 0; I < NumInputs; ++I) {
     InputFileInfo IFI = getInputFileInfo(MF, I + 1);
-    if (IFI.TopLevelModuleMap)
+    if (IFI.TopLevel && IFI.ModuleMap)
       if (auto FE = getInputFile(MF, I + 1).getFile())
         Visitor(*FE);
   }

clang/lib/Serialization/ASTWriter.cpp

@@ -1525,7 +1525,8 @@ struct InputFileEntry {
   bool IsSystemFile;
   bool IsTransient;
   bool BufferOverridden;
-  bool IsTopLevelModuleMap;
+  bool IsTopLevel;
+  bool IsModuleMap;
   uint32_t ContentHash[2];
 
   InputFileEntry(FileEntryRef File) : File(File) {}
@@ -1547,8 +1548,10 @@ void ASTWriter::WriteInputFiles(SourceManager &SourceMgr,
   IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 32)); // Modification time
   IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Overridden
   IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Transient
+  IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Top-level
   IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Module map
-  IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // File name
+  IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 16)); // Name as req. len
+  IFAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // Name as req. + name
   unsigned IFAbbrevCode = Stream.EmitAbbrev(std::move(IFAbbrev));
 
   // Create input file hash abbreviation.
@@ -1582,8 +1585,8 @@ void ASTWriter::WriteInputFiles(SourceManager &SourceMgr,
     Entry.IsSystemFile = isSystem(File.getFileCharacteristic());
     Entry.IsTransient = Cache->IsTransient;
     Entry.BufferOverridden = Cache->BufferOverridden;
-    Entry.IsTopLevelModuleMap = isModuleMap(File.getFileCharacteristic()) &&
-                                File.getIncludeLoc().isInvalid();
+    Entry.IsTopLevel = File.getIncludeLoc().isInvalid();
+    Entry.IsModuleMap = isModuleMap(File.getFileCharacteristic());
 
     auto ContentHash = hash_code(-1);
     if (PP->getHeaderSearchInfo()
@@ -1631,16 +1634,28 @@ void ASTWriter::WriteInputFiles(SourceManager &SourceMgr,
     // Emit size/modification time for this file.
     // And whether this file was overridden.
     {
+      SmallString<128> NameAsRequested = Entry.File.getNameAsRequested();
+      SmallString<128> Name = Entry.File.getName();
+
+      PreparePathForOutput(NameAsRequested);
+      PreparePathForOutput(Name);
+
+      if (Name == NameAsRequested)
+        Name.clear();
+
       RecordData::value_type Record[] = {
           INPUT_FILE,
           InputFileOffsets.size(),
           (uint64_t)Entry.File.getSize(),
           (uint64_t)getTimestampForOutput(Entry.File),
           Entry.BufferOverridden,
           Entry.IsTransient,
-          Entry.IsTopLevelModuleMap};
+          Entry.IsTopLevel,
+          Entry.IsModuleMap,
+          NameAsRequested.size()};
 
-      EmitRecordWithPath(IFAbbrevCode, Record, Entry.File.getNameAsRequested());
+      Stream.EmitRecordWithBlob(IFAbbrevCode, Record,
+                                (NameAsRequested + Name).str());
     }
 
     // Emit content hash for this file.

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

@@ -459,30 +459,35 @@ ModuleDepCollectorPP::handleTopLevelModule(const Module *M) {
   serialization::ModuleFile *MF =
       MDC.ScanInstance.getASTReader()->getModuleManager().lookup(
           M->getASTFile());
-  MDC.ScanInstance.getASTReader()->visitInputFiles(
-      *MF, true, true, [&](const serialization::InputFile &IF, bool isSystem) {
+  MDC.ScanInstance.getASTReader()->visitInputFileInfos(
+      *MF, /*IncludeSystem=*/true,
+      [&](const serialization::InputFileInfo &IFI, bool IsSystem) {
         // __inferred_module.map is the result of the way in which an implicit
         // module build handles inferred modules. It adds an overlay VFS with
         // this file in the proper directory and relies on the rest of Clang to
         // handle it like normal. With explicitly built modules we don't need
         // to play VFS tricks, so replace it with the correct module map.
-        if (IF.getFile()->getName().endswith("__inferred_module.map")) {
+        if (StringRef(IFI.Filename).endswith("__inferred_module.map")) {
           MDC.addFileDep(MD, ModuleMap->getName());
           return;
         }
-        MDC.addFileDep(MD, IF.getFile()->getName());
+        MDC.addFileDep(MD, IFI.Filename);
       });
 
   llvm::DenseSet<const Module *> SeenDeps;
   addAllSubmodulePrebuiltDeps(M, MD, SeenDeps);
   addAllSubmoduleDeps(M, MD, SeenDeps);
   addAllAffectingClangModules(M, MD, SeenDeps);
 
-  MDC.ScanInstance.getASTReader()->visitTopLevelModuleMaps(
-      *MF, [&](FileEntryRef FE) {
-        if (FE.getNameAsRequested().endswith("__inferred_module.map"))
+  MDC.ScanInstance.getASTReader()->visitInputFileInfos(
+      *MF, /*IncludeSystem=*/true,
+      [&](const serialization::InputFileInfo &IFI, bool IsSystem) {
+        if (!(IFI.TopLevel && IFI.ModuleMap))
           return;
-        MD.ModuleMapFileDeps.emplace_back(FE.getNameAsRequested());
+        if (StringRef(IFI.FilenameAsRequested)
+                .endswith("__inferred_module.map"))
+          return;
+        MD.ModuleMapFileDeps.emplace_back(IFI.FilenameAsRequested);
       });
 
   CompilerInvocation CI = MDC.makeInvocationForModuleBuildWithoutOutputs(