Add the clang library to the repo (with some of my changes, too).

1 files changed, 2775 insertions, 0 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
new file mode 100644
index 0000000..7aa9603
--- /dev/null
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -0,0 +1,2775 @@
+//===--- ASTUnit.cpp - ASTUnit utility ------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// ASTUnit Implementation.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTConsumer.h"
+#include "clang/AST/DeclVisitor.h"
+#include "clang/AST/TypeOrdering.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/Driver/Compilation.h"
+#include "clang/Driver/Driver.h"
+#include "clang/Driver/Job.h"
+#include "clang/Driver/ArgList.h"
+#include "clang/Driver/Options.h"
+#include "clang/Driver/Tool.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/Frontend/FrontendDiagnostic.h"
+#include "clang/Frontend/FrontendOptions.h"
+#include "clang/Frontend/MultiplexConsumer.h"
+#include "clang/Frontend/Utils.h"
+#include "clang/Serialization/ASTReader.h"
+#include "clang/Serialization/ASTWriter.h"
+#include "clang/Lex/HeaderSearch.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Basic/TargetOptions.h"
+#include "clang/Basic/TargetInfo.h"
+#include "clang/Basic/Diagnostic.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSet.h"
+#include "llvm/Support/Atomic.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Timer.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Mutex.h"
+#include "llvm/Support/MutexGuard.h"
+#include "llvm/Support/CrashRecoveryContext.h"
+#include <cstdlib>
+#include <cstdio>
+#include <sys/stat.h>
+using namespace clang;
+
+using llvm::TimeRecord;
+
+namespace {
+  class SimpleTimer {
+    bool WantTiming;
+    TimeRecord Start;
+    std::string Output;
+
+  public:
+    explicit SimpleTimer(bool WantTiming) : WantTiming(WantTiming) {
+      if (WantTiming)
+        Start = TimeRecord::getCurrentTime();
+    }
+
+    void setOutput(const Twine &Output) {
+      if (WantTiming)
+        this->Output = Output.str();
+    }
+
+    ~SimpleTimer() {
+      if (WantTiming) {
+        TimeRecord Elapsed = TimeRecord::getCurrentTime();
+        Elapsed -= Start;
+        llvm::errs() << Output << ':';
+        Elapsed.print(Elapsed, llvm::errs());
+        llvm::errs() << '\n';
+      }
+    }
+  };
+  
+  struct OnDiskData {
+    /// \brief The file in which the precompiled preamble is stored.
+    std::string PreambleFile;
+
+    /// \brief Temporary files that should be removed when the ASTUnit is 
+    /// destroyed.
+    SmallVector<llvm::sys::Path, 4> TemporaryFiles;
+    
+    /// \brief Erase temporary files.
+    void CleanTemporaryFiles();
+
+    /// \brief Erase the preamble file.
+    void CleanPreambleFile();
+
+    /// \brief Erase temporary files and the preamble file.
+    void Cleanup();
+  };
+}
+
+static llvm::sys::SmartMutex<false> &getOnDiskMutex() {
+  static llvm::sys::SmartMutex<false> M(/* recursive = */ true);
+  return M;
+}
+
+static void cleanupOnDiskMapAtExit(void);
+
+typedef llvm::DenseMap<const ASTUnit *, OnDiskData *> OnDiskDataMap;
+static OnDiskDataMap &getOnDiskDataMap() {
+  static OnDiskDataMap M;
+  static bool hasRegisteredAtExit = false;
+  if (!hasRegisteredAtExit) {
+    hasRegisteredAtExit = true;
+    atexit(cleanupOnDiskMapAtExit);
+  }
+  return M;
+}
+
+static void cleanupOnDiskMapAtExit(void) {
+  // No mutex required here since we are leaving the program.
+  OnDiskDataMap &M = getOnDiskDataMap();
+  for (OnDiskDataMap::iterator I = M.begin(), E = M.end(); I != E; ++I) {
+    // We don't worry about freeing the memory associated with OnDiskDataMap.
+    // All we care about is erasing stale files.
+    I->second->Cleanup();
+  }
+}
+
+static OnDiskData &getOnDiskData(const ASTUnit *AU) {
+  // We require the mutex since we are modifying the structure of the
+  // DenseMap.
+  llvm::MutexGuard Guard(getOnDiskMutex());
+  OnDiskDataMap &M = getOnDiskDataMap();
+  OnDiskData *&D = M[AU];
+  if (!D)
+    D = new OnDiskData();
+  return *D;
+}
+
+static void erasePreambleFile(const ASTUnit *AU) {
+  getOnDiskData(AU).CleanPreambleFile();
+}
+
+static void removeOnDiskEntry(const ASTUnit *AU) {
+  // We require the mutex since we are modifying the structure of the
+  // DenseMap.
+  llvm::MutexGuard Guard(getOnDiskMutex());
+  OnDiskDataMap &M = getOnDiskDataMap();
+  OnDiskDataMap::iterator I = M.find(AU);
+  if (I != M.end()) {
+    I->second->Cleanup();
+    delete I->second;
+    M.erase(AU);
+  }
+}
+
+static void setPreambleFile(const ASTUnit *AU, llvm::StringRef preambleFile) {
+  getOnDiskData(AU).PreambleFile = preambleFile;
+}
+
+static const std::string &getPreambleFile(const ASTUnit *AU) {
+  return getOnDiskData(AU).PreambleFile;  
+}
+
+void OnDiskData::CleanTemporaryFiles() {
+  for (unsigned I = 0, N = TemporaryFiles.size(); I != N; ++I)
+    TemporaryFiles[I].eraseFromDisk();
+  TemporaryFiles.clear(); 
+}
+
+void OnDiskData::CleanPreambleFile() {
+  if (!PreambleFile.empty()) {
+    llvm::sys::Path(PreambleFile).eraseFromDisk();
+    PreambleFile.clear();
+  }
+}
+
+void OnDiskData::Cleanup() {
+  CleanTemporaryFiles();
+  CleanPreambleFile();
+}
+
+void ASTUnit::clearFileLevelDecls() {
+  for (FileDeclsTy::iterator
+         I = FileDecls.begin(), E = FileDecls.end(); I != E; ++I)
+    delete I->second;
+  FileDecls.clear();
+}
+
+void ASTUnit::CleanTemporaryFiles() {
+  getOnDiskData(this).CleanTemporaryFiles();
+}
+
+void ASTUnit::addTemporaryFile(const llvm::sys::Path &TempFile) {
+  getOnDiskData(this).TemporaryFiles.push_back(TempFile);
+}
+
+/// \brief After failing to build a precompiled preamble (due to
+/// errors in the source that occurs in the preamble), the number of
+/// reparses during which we'll skip even trying to precompile the
+/// preamble.
+const unsigned DefaultPreambleRebuildInterval = 5;
+
+/// \brief Tracks the number of ASTUnit objects that are currently active.
+///
+/// Used for debugging purposes only.
+static llvm::sys::cas_flag ActiveASTUnitObjects;
+
+ASTUnit::ASTUnit(bool _MainFileIsAST)
+  : Reader(0), OnlyLocalDecls(false), CaptureDiagnostics(false),
+    MainFileIsAST(_MainFileIsAST), 
+    TUKind(TU_Complete), WantTiming(getenv("LIBCLANG_TIMING")),
+    OwnsRemappedFileBuffers(true),
+    NumStoredDiagnosticsFromDriver(0),
+    PreambleRebuildCounter(0), SavedMainFileBuffer(0), PreambleBuffer(0),
+    NumWarningsInPreamble(0),
+    ShouldCacheCodeCompletionResults(false),
+    CompletionCacheTopLevelHashValue(0),
+    PreambleTopLevelHashValue(0),
+    CurrentTopLevelHashValue(0),
+    UnsafeToFree(false) { 
+  if (getenv("LIBCLANG_OBJTRACKING")) {
+    llvm::sys::AtomicIncrement(&ActiveASTUnitObjects);
+    fprintf(stderr, "+++ %d translation units\n", ActiveASTUnitObjects);
+  }    
+}
+
+ASTUnit::~ASTUnit() {
+  clearFileLevelDecls();
+
+  // Clean up the temporary files and the preamble file.
+  removeOnDiskEntry(this);
+
+  // Free the buffers associated with remapped files. We are required to
+  // perform this operation here because we explicitly request that the
+  // compiler instance *not* free these buffers for each invocation of the
+  // parser.
+  if (Invocation.getPtr() && OwnsRemappedFileBuffers) {
+    PreprocessorOptions &PPOpts = Invocation->getPreprocessorOpts();
+    for (PreprocessorOptions::remapped_file_buffer_iterator
+           FB = PPOpts.remapped_file_buffer_begin(),
+           FBEnd = PPOpts.remapped_file_buffer_end();
+         FB != FBEnd;
+         ++FB)
+      delete FB->second;
+  }
+  
+  delete SavedMainFileBuffer;
+  delete PreambleBuffer;
+
+  ClearCachedCompletionResults();  
+  
+  if (getenv("LIBCLANG_OBJTRACKING")) {
+    llvm::sys::AtomicDecrement(&ActiveASTUnitObjects);
+    fprintf(stderr, "--- %d translation units\n", ActiveASTUnitObjects);
+  }    
+}
+
+void ASTUnit::setPreprocessor(Preprocessor *pp) { PP = pp; }
+
+/// \brief Determine the set of code-completion contexts in which this 
+/// declaration should be shown.
+static unsigned getDeclShowContexts(NamedDecl *ND,
+                                    const LangOptions &LangOpts,
+                                    bool &IsNestedNameSpecifier) {
+  IsNestedNameSpecifier = false;
+  
+  if (isa<UsingShadowDecl>(ND))
+    ND = dyn_cast<NamedDecl>(ND->getUnderlyingDecl());
+  if (!ND)
+    return 0;
+  
+  unsigned Contexts = 0;
+  if (isa<TypeDecl>(ND) || isa<ObjCInterfaceDecl>(ND) || 
+      isa<ClassTemplateDecl>(ND) || isa<TemplateTemplateParmDecl>(ND)) {
+    // Types can appear in these contexts.
+    if (LangOpts.CPlusPlus || !isa<TagDecl>(ND))
+      Contexts |= (1 << (CodeCompletionContext::CCC_TopLevel - 1))
+                | (1 << (CodeCompletionContext::CCC_ObjCIvarList - 1))
+                | (1 << (CodeCompletionContext::CCC_ClassStructUnion - 1))
+                | (1 << (CodeCompletionContext::CCC_Statement - 1))
+                | (1 << (CodeCompletionContext::CCC_Type - 1))
+              | (1 << (CodeCompletionContext::CCC_ParenthesizedExpression - 1));
+
+    // In C++, types can appear in expressions contexts (for functional casts).
+    if (LangOpts.CPlusPlus)
+      Contexts |= (1 << (CodeCompletionContext::CCC_Expression - 1));
+    
+    // In Objective-C, message sends can send interfaces. In Objective-C++,
+    // all types are available due to functional casts.
+    if (LangOpts.CPlusPlus || isa<ObjCInterfaceDecl>(ND))
+      Contexts |= (1 << (CodeCompletionContext::CCC_ObjCMessageReceiver - 1));
+    
+    // In Objective-C, you can only be a subclass of another Objective-C class
+    if (isa<ObjCInterfaceDecl>(ND))
+      Contexts |= (1 << (CodeCompletionContext::CCC_ObjCInterfaceName - 1));
+
+    // Deal with tag names.
+    if (isa<EnumDecl>(ND)) {
+      Contexts |= (1 << (CodeCompletionContext::CCC_EnumTag - 1));
+      
+      // Part of the nested-name-specifier in C++0x.
+      if (LangOpts.CPlusPlus0x)
+        IsNestedNameSpecifier = true;
+    } else if (RecordDecl *Record = dyn_cast<RecordDecl>(ND)) {
+      if (Record->isUnion())
+        Contexts |= (1 << (CodeCompletionContext::CCC_UnionTag - 1));
+      else
+        Contexts |= (1 << (CodeCompletionContext::CCC_ClassOrStructTag - 1));
+      
+      if (LangOpts.CPlusPlus)
+        IsNestedNameSpecifier = true;
+    } else if (isa<ClassTemplateDecl>(ND))
+      IsNestedNameSpecifier = true;
+  } else if (isa<ValueDecl>(ND) || isa<FunctionTemplateDecl>(ND)) {
+    // Values can appear in these contexts.
+    Contexts = (1 << (CodeCompletionContext::CCC_Statement - 1))
+             | (1 << (CodeCompletionContext::CCC_Expression - 1))
+             | (1 << (CodeCompletionContext::CCC_ParenthesizedExpression - 1))
+             | (1 << (CodeCompletionContext::CCC_ObjCMessageReceiver - 1));
+  } else if (isa<ObjCProtocolDecl>(ND)) {
+    Contexts = (1 << (CodeCompletionContext::CCC_ObjCProtocolName - 1));
+  } else if (isa<ObjCCategoryDecl>(ND)) {
+    Contexts = (1 << (CodeCompletionContext::CCC_ObjCCategoryName - 1));
+  } else if (isa<NamespaceDecl>(ND) || isa<NamespaceAliasDecl>(ND)) {
+    Contexts = (1 << (CodeCompletionContext::CCC_Namespace - 1));
+   
+    // Part of the nested-name-specifier.
+    IsNestedNameSpecifier = true;
+  }
+  
+  return Contexts;
+}
+
+void ASTUnit::CacheCodeCompletionResults() {
+  if (!TheSema)
+    return;
+  
+  SimpleTimer Timer(WantTiming);
+  Timer.setOutput("Cache global code completions for " + getMainFileName());
+
+  // Clear out the previous results.
+  ClearCachedCompletionResults();
+  
+  // Gather the set of global code completions.
+  typedef CodeCompletionResult Result;
+  SmallVector<Result, 8> Results;
+  CachedCompletionAllocator = new GlobalCodeCompletionAllocator;
+  TheSema->GatherGlobalCodeCompletions(*CachedCompletionAllocator,
+                                       getCodeCompletionTUInfo(), Results);
+  
+  // Translate global code completions into cached completions.
+  llvm::DenseMap<CanQualType, unsigned> CompletionTypes;
+  
+  for (unsigned I = 0, N = Results.size(); I != N; ++I) {
+    switch (Results[I].Kind) {
+    case Result::RK_Declaration: {
+      bool IsNestedNameSpecifier = false;
+      CachedCodeCompletionResult CachedResult;
+      CachedResult.Completion = Results[I].CreateCodeCompletionString(*TheSema,
+                                                    *CachedCompletionAllocator,
+                                                    getCodeCompletionTUInfo());
+      CachedResult.ShowInContexts = getDeclShowContexts(Results[I].Declaration,
+                                                        Ctx->getLangOpts(),
+                                                        IsNestedNameSpecifier);
+      CachedResult.Priority = Results[I].Priority;
+      CachedResult.Kind = Results[I].CursorKind;
+      CachedResult.Availability = Results[I].Availability;
+
+      // Keep track of the type of this completion in an ASTContext-agnostic 
+      // way.
+      QualType UsageType = getDeclUsageType(*Ctx, Results[I].Declaration);
+      if (UsageType.isNull()) {
+        CachedResult.TypeClass = STC_Void;
+        CachedResult.Type = 0;
+      } else {
+        CanQualType CanUsageType
+          = Ctx->getCanonicalType(UsageType.getUnqualifiedType());
+        CachedResult.TypeClass = getSimplifiedTypeClass(CanUsageType);
+
+        // Determine whether we have already seen this type. If so, we save
+        // ourselves the work of formatting the type string by using the 
+        // temporary, CanQualType-based hash table to find the associated value.
+        unsigned &TypeValue = CompletionTypes[CanUsageType];
+        if (TypeValue == 0) {
+          TypeValue = CompletionTypes.size();
+          CachedCompletionTypes[QualType(CanUsageType).getAsString()]
+            = TypeValue;
+        }
+        
+        CachedResult.Type = TypeValue;
+      }
+      
+      CachedCompletionResults.push_back(CachedResult);
+      
+      /// Handle nested-name-specifiers in C++.
+      if (TheSema->Context.getLangOpts().CPlusPlus && 
+          IsNestedNameSpecifier && !Results[I].StartsNestedNameSpecifier) {
+        // The contexts in which a nested-name-specifier can appear in C++.
+        unsigned NNSContexts
+          = (1 << (CodeCompletionContext::CCC_TopLevel - 1))
+          | (1 << (CodeCompletionContext::CCC_ObjCIvarList - 1))
+          | (1 << (CodeCompletionContext::CCC_ClassStructUnion - 1))
+          | (1 << (CodeCompletionContext::CCC_Statement - 1))
+          | (1 << (CodeCompletionContext::CCC_Expression - 1))
+          | (1 << (CodeCompletionContext::CCC_ObjCMessageReceiver - 1))
+          | (1 << (CodeCompletionContext::CCC_EnumTag - 1))
+          | (1 << (CodeCompletionContext::CCC_UnionTag - 1))
+          | (1 << (CodeCompletionContext::CCC_ClassOrStructTag - 1))
+          | (1 << (CodeCompletionContext::CCC_Type - 1))
+          | (1 << (CodeCompletionContext::CCC_PotentiallyQualifiedName - 1))
+          | (1 << (CodeCompletionContext::CCC_ParenthesizedExpression - 1));
+
+        if (isa<NamespaceDecl>(Results[I].Declaration) ||
+            isa<NamespaceAliasDecl>(Results[I].Declaration))
+          NNSContexts |= (1 << (CodeCompletionContext::CCC_Namespace - 1));
+
+        if (unsigned RemainingContexts 
+                                = NNSContexts & ~CachedResult.ShowInContexts) {
+          // If there any contexts where this completion can be a 
+          // nested-name-specifier but isn't already an option, create a 
+          // nested-name-specifier completion.
+          Results[I].StartsNestedNameSpecifier = true;
+          CachedResult.Completion 
+            = Results[I].CreateCodeCompletionString(*TheSema,
+                                                    *CachedCompletionAllocator,
+                                                    getCodeCompletionTUInfo());
+          CachedResult.ShowInContexts = RemainingContexts;
+          CachedResult.Priority = CCP_NestedNameSpecifier;
+          CachedResult.TypeClass = STC_Void;
+          CachedResult.Type = 0;
+          CachedCompletionResults.push_back(CachedResult);
+        }
+      }
+      break;
+    }
+        
+    case Result::RK_Keyword:
+    case Result::RK_Pattern:
+      // Ignore keywords and patterns; we don't care, since they are so
+      // easily regenerated.
+      break;
+      
+    case Result::RK_Macro: {
+      CachedCodeCompletionResult CachedResult;
+      CachedResult.Completion 
+        = Results[I].CreateCodeCompletionString(*TheSema,
+                                                *CachedCompletionAllocator,
+                                                getCodeCompletionTUInfo());
+      CachedResult.ShowInContexts
+        = (1 << (CodeCompletionContext::CCC_TopLevel - 1))
+        | (1 << (CodeCompletionContext::CCC_ObjCInterface - 1))
+        | (1 << (CodeCompletionContext::CCC_ObjCImplementation - 1))
+        | (1 << (CodeCompletionContext::CCC_ObjCIvarList - 1))
+        | (1 << (CodeCompletionContext::CCC_ClassStructUnion - 1))
+        | (1 << (CodeCompletionContext::CCC_Statement - 1))
+        | (1 << (CodeCompletionContext::CCC_Expression - 1))
+        | (1 << (CodeCompletionContext::CCC_ObjCMessageReceiver - 1))
+        | (1 << (CodeCompletionContext::CCC_MacroNameUse - 1))
+        | (1 << (CodeCompletionContext::CCC_PreprocessorExpression - 1))
+        | (1 << (CodeCompletionContext::CCC_ParenthesizedExpression - 1))
+        | (1 << (CodeCompletionContext::CCC_OtherWithMacros - 1));
+      
+      CachedResult.Priority = Results[I].Priority;
+      CachedResult.Kind = Results[I].CursorKind;
+      CachedResult.Availability = Results[I].Availability;
+      CachedResult.TypeClass = STC_Void;
+      CachedResult.Type = 0;
+      CachedCompletionResults.push_back(CachedResult);
+      break;
+    }
+    }
+  }
+  
+  // Save the current top-level hash value.
+  CompletionCacheTopLevelHashValue = CurrentTopLevelHashValue;
+}
+
+void ASTUnit::ClearCachedCompletionResults() {
+  CachedCompletionResults.clear();
+  CachedCompletionTypes.clear();
+  CachedCompletionAllocator = 0;
+}
+
+namespace {
+
+/// \brief Gathers information from ASTReader that will be used to initialize
+/// a Preprocessor.
+class ASTInfoCollector : public ASTReaderListener {
+  Preprocessor &PP;
+  ASTContext &Context;
+  LangOptions &LangOpt;
+  HeaderSearch &HSI;
+  IntrusiveRefCntPtr<TargetInfo> &Target;
+  std::string &Predefines;
+  unsigned &Counter;
+
+  unsigned NumHeaderInfos;
+
+  bool InitializedLanguage;
+public:
+  ASTInfoCollector(Preprocessor &PP, ASTContext &Context, LangOptions &LangOpt, 
+                   HeaderSearch &HSI,
+                   IntrusiveRefCntPtr<TargetInfo> &Target,
+                   std::string &Predefines,
+                   unsigned &Counter)
+    : PP(PP), Context(Context), LangOpt(LangOpt), HSI(HSI), Target(Target),
+      Predefines(Predefines), Counter(Counter), NumHeaderInfos(0),
+      InitializedLanguage(false) {}
+
+  virtual bool ReadLanguageOptions(const LangOptions &LangOpts) {
+    if (InitializedLanguage)
+      return false;
+    
+    LangOpt = LangOpts;
+    
+    // Initialize the preprocessor.
+    PP.Initialize(*Target);
+    
+    // Initialize the ASTContext
+    Context.InitBuiltinTypes(*Target);
+    
+    InitializedLanguage = true;
+    return false;
+  }
+
+  virtual bool ReadTargetTriple(StringRef Triple) {
+    // If we've already initialized the target, don't do it again.
+    if (Target)
+      return false;
+    
+    // FIXME: This is broken, we should store the TargetOptions in the AST file.
+    TargetOptions TargetOpts;
+    TargetOpts.ABI = "";
+    TargetOpts.CXXABI = "";
+    TargetOpts.CPU = "";
+    TargetOpts.Features.clear();
+    TargetOpts.Triple = Triple;
+    Target = TargetInfo::CreateTargetInfo(PP.getDiagnostics(), TargetOpts);
+    return false;
+  }
+
+  virtual bool ReadPredefinesBuffer(const PCHPredefinesBlocks &Buffers,
+                                    StringRef OriginalFileName,
+                                    std::string &SuggestedPredefines,
+                                    FileManager &FileMgr) {
+    Predefines = Buffers[0].Data;
+    for (unsigned I = 1, N = Buffers.size(); I != N; ++I) {
+      Predefines += Buffers[I].Data;
+    }
+    return false;
+  }
+
+  virtual void ReadHeaderFileInfo(const HeaderFileInfo &HFI, unsigned ID) {
+    HSI.setHeaderFileInfoForUID(HFI, NumHeaderInfos++);
+  }
+
+  virtual void ReadCounter(unsigned Value) {
+    Counter = Value;
+  }
+};
+
+class StoredDiagnosticConsumer : public DiagnosticConsumer {
+  SmallVectorImpl<StoredDiagnostic> &StoredDiags;
+  
+public:
+  explicit StoredDiagnosticConsumer(
+                          SmallVectorImpl<StoredDiagnostic> &StoredDiags)
+    : StoredDiags(StoredDiags) { }
+  
+  virtual void HandleDiagnostic(DiagnosticsEngine::Level Level,
+                                const Diagnostic &Info);
+  
+  DiagnosticConsumer *clone(DiagnosticsEngine &Diags) const {
+    // Just drop any diagnostics that come from cloned consumers; they'll
+    // have different source managers anyway.
+    // FIXME: We'd like to be able to capture these somehow, even if it's just
+    // file/line/column, because they could occur when parsing module maps or
+    // building modules on-demand.
+    return new IgnoringDiagConsumer();
+  }
+};
+
+/// \brief RAII object that optionally captures diagnostics, if
+/// there is no diagnostic client to capture them already.
+class CaptureDroppedDiagnostics {
+  DiagnosticsEngine &Diags;
+  StoredDiagnosticConsumer Client;
+  DiagnosticConsumer *PreviousClient;
+
+public:
+  CaptureDroppedDiagnostics(bool RequestCapture, DiagnosticsEngine &Diags,
+                          SmallVectorImpl<StoredDiagnostic> &StoredDiags)
+    : Diags(Diags), Client(StoredDiags), PreviousClient(0)
+  {
+    if (RequestCapture || Diags.getClient() == 0) {
+      PreviousClient = Diags.takeClient();
+      Diags.setClient(&Client);
+    }
+  }
+
+  ~CaptureDroppedDiagnostics() {
+    if (Diags.getClient() == &Client) {
+      Diags.takeClient();
+      Diags.setClient(PreviousClient);
+    }
+  }
+};
+
+} // anonymous namespace
+
+void StoredDiagnosticConsumer::HandleDiagnostic(DiagnosticsEngine::Level Level,
+                                              const Diagnostic &Info) {
+  // Default implementation (Warnings/errors count).
+  DiagnosticConsumer::HandleDiagnostic(Level, Info);
+
+  StoredDiags.push_back(StoredDiagnostic(Level, Info));
+}
+
+const std::string &ASTUnit::getOriginalSourceFileName() {
+  return OriginalSourceFile;
+}
+
+llvm::MemoryBuffer *ASTUnit::getBufferForFile(StringRef Filename,
+                                              std::string *ErrorStr) {
+  assert(FileMgr);
+  return FileMgr->getBufferForFile(Filename, ErrorStr);
+}
+
+/// \brief Configure the diagnostics object for use with ASTUnit.
+void ASTUnit::ConfigureDiags(IntrusiveRefCntPtr<DiagnosticsEngine> &Diags,
+                             const char **ArgBegin, const char **ArgEnd,
+                             ASTUnit &AST, bool CaptureDiagnostics) {
+  if (!Diags.getPtr()) {
+    // No diagnostics engine was provided, so create our own diagnostics object
+    // with the default options.
+    DiagnosticOptions DiagOpts;
+    DiagnosticConsumer *Client = 0;
+    if (CaptureDiagnostics)
+      Client = new StoredDiagnosticConsumer(AST.StoredDiagnostics);
+    Diags = CompilerInstance::createDiagnostics(DiagOpts, ArgEnd-ArgBegin,
+                                                ArgBegin, Client,
+                                                /*ShouldOwnClient=*/true,
+                                                /*ShouldCloneClient=*/false);
+  } else if (CaptureDiagnostics) {
+    Diags->setClient(new StoredDiagnosticConsumer(AST.StoredDiagnostics));
+  }
+}
+
+ASTUnit *ASTUnit::LoadFromASTFile(const std::string &Filename,
+                              IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+                                  const FileSystemOptions &FileSystemOpts,
+                                  bool OnlyLocalDecls,
+                                  RemappedFile *RemappedFiles,
+                                  unsigned NumRemappedFiles,
+                                  bool CaptureDiagnostics,
+                                  bool AllowPCHWithCompilerErrors) {
+  OwningPtr<ASTUnit> AST(new ASTUnit(true));
+
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<ASTUnit>
+    ASTUnitCleanup(AST.get());
+  llvm::CrashRecoveryContextCleanupRegistrar<DiagnosticsEngine,
+    llvm::CrashRecoveryContextReleaseRefCleanup<DiagnosticsEngine> >
+    DiagCleanup(Diags.getPtr());
+
+  ConfigureDiags(Diags, 0, 0, *AST, CaptureDiagnostics);
+
+  AST->OnlyLocalDecls = OnlyLocalDecls;
+  AST->CaptureDiagnostics = CaptureDiagnostics;
+  AST->Diagnostics = Diags;
+  AST->FileMgr = new FileManager(FileSystemOpts);
+  AST->SourceMgr = new SourceManager(AST->getDiagnostics(),
+                                     AST->getFileManager());
+  AST->HeaderInfo.reset(new HeaderSearch(AST->getFileManager(),
+                                         AST->getDiagnostics(),
+                                         AST->ASTFileLangOpts,
+                                         /*Target=*/0));
+  
+  for (unsigned I = 0; I != NumRemappedFiles; ++I) {
+    FilenameOrMemBuf fileOrBuf = RemappedFiles[I].second;
+    if (const llvm::MemoryBuffer *
+          memBuf = fileOrBuf.dyn_cast<const llvm::MemoryBuffer *>()) {
+      // Create the file entry for the file that we're mapping from.
+      const FileEntry *FromFile
+        = AST->getFileManager().getVirtualFile(RemappedFiles[I].first,
+                                               memBuf->getBufferSize(),
+                                               0);
+      if (!FromFile) {
+        AST->getDiagnostics().Report(diag::err_fe_remap_missing_from_file)
+          << RemappedFiles[I].first;
+        delete memBuf;
+        continue;
+      }
+      
+      // Override the contents of the "from" file with the contents of
+      // the "to" file.
+      AST->getSourceManager().overrideFileContents(FromFile, memBuf);
+
+    } else {
+      const char *fname = fileOrBuf.get<const char *>();
+      const FileEntry *ToFile = AST->FileMgr->getFile(fname);
+      if (!ToFile) {
+        AST->getDiagnostics().Report(diag::err_fe_remap_missing_to_file)
+        << RemappedFiles[I].first << fname;
+        continue;
+      }
+
+      // Create the file entry for the file that we're mapping from.
+      const FileEntry *FromFile
+        = AST->getFileManager().getVirtualFile(RemappedFiles[I].first,
+                                               ToFile->getSize(),
+                                               0);
+      if (!FromFile) {
+        AST->getDiagnostics().Report(diag::err_fe_remap_missing_from_file)
+          << RemappedFiles[I].first;
+        delete memBuf;
+        continue;
+      }
+      
+      // Override the contents of the "from" file with the contents of
+      // the "to" file.
+      AST->getSourceManager().overrideFileContents(FromFile, ToFile);
+    }
+  }
+  
+  // Gather Info for preprocessor construction later on.
+
+  HeaderSearch &HeaderInfo = *AST->HeaderInfo.get();
+  std::string Predefines;
+  unsigned Counter;
+
+  OwningPtr<ASTReader> Reader;
+
+  AST->PP = new Preprocessor(AST->getDiagnostics(), AST->ASTFileLangOpts, 
+                             /*Target=*/0, AST->getSourceManager(), HeaderInfo, 
+                             *AST, 
+                             /*IILookup=*/0,
+                             /*OwnsHeaderSearch=*/false,
+                             /*DelayInitialization=*/true);
+  Preprocessor &PP = *AST->PP;
+
+  AST->Ctx = new ASTContext(AST->ASTFileLangOpts,
+                            AST->getSourceManager(),
+                            /*Target=*/0,
+                            PP.getIdentifierTable(),
+                            PP.getSelectorTable(),
+                            PP.getBuiltinInfo(),
+                            /* size_reserve = */0,
+                            /*DelayInitialization=*/true);
+  ASTContext &Context = *AST->Ctx;
+
+  Reader.reset(new ASTReader(PP, Context,
+                             /*isysroot=*/"",
+                             /*DisableValidation=*/false,
+                             /*DisableStatCache=*/false,
+                             AllowPCHWithCompilerErrors));
+  
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<ASTReader>
+    ReaderCleanup(Reader.get());
+
+  Reader->setListener(new ASTInfoCollector(*AST->PP, Context,
+                                           AST->ASTFileLangOpts, HeaderInfo, 
+                                           AST->Target, Predefines, Counter));
+
+  switch (Reader->ReadAST(Filename, serialization::MK_MainFile)) {
+  case ASTReader::Success:
+    break;
+
+  case ASTReader::Failure:
+  case ASTReader::IgnorePCH:
+    AST->getDiagnostics().Report(diag::err_fe_unable_to_load_pch);
+    return NULL;
+  }
+
+  AST->OriginalSourceFile = Reader->getOriginalSourceFile();
+
+  PP.setPredefines(Reader->getSuggestedPredefines());
+  PP.setCounterValue(Counter);
+
+  // Attach the AST reader to the AST context as an external AST
+  // source, so that declarations will be deserialized from the
+  // AST file as needed.
+  ASTReader *ReaderPtr = Reader.get();
+  OwningPtr<ExternalASTSource> Source(Reader.take());
+
+  // Unregister the cleanup for ASTReader.  It will get cleaned up
+  // by the ASTUnit cleanup.
+  ReaderCleanup.unregister();
+
+  Context.setExternalSource(Source);
+
+  // Create an AST consumer, even though it isn't used.
+  AST->Consumer.reset(new ASTConsumer);
+  
+  // Create a semantic analysis object and tell the AST reader about it.
+  AST->TheSema.reset(new Sema(PP, Context, *AST->Consumer));
+  AST->TheSema->Initialize();
+  ReaderPtr->InitializeSema(*AST->TheSema);
+  AST->Reader = ReaderPtr;
+
+  return AST.take();
+}
+
+namespace {
+
+/// \brief Preprocessor callback class that updates a hash value with the names 
+/// of all macros that have been defined by the translation unit.
+class MacroDefinitionTrackerPPCallbacks : public PPCallbacks {
+  unsigned &Hash;
+  
+public:
+  explicit MacroDefinitionTrackerPPCallbacks(unsigned &Hash) : Hash(Hash) { }
+  
+  virtual void MacroDefined(const Token &MacroNameTok, const MacroInfo *MI) {
+    Hash = llvm::HashString(MacroNameTok.getIdentifierInfo()->getName(), Hash);
+  }
+};
+
+/// \brief Add the given declaration to the hash of all top-level entities.
+void AddTopLevelDeclarationToHash(Decl *D, unsigned &Hash) {
+  if (!D)
+    return;
+  
+  DeclContext *DC = D->getDeclContext();
+  if (!DC)
+    return;
+  
+  if (!(DC->isTranslationUnit() || DC->getLookupParent()->isTranslationUnit()))
+    return;
+
+  if (NamedDecl *ND = dyn_cast<NamedDecl>(D)) {
+    if (ND->getIdentifier())
+      Hash = llvm::HashString(ND->getIdentifier()->getName(), Hash);
+    else if (DeclarationName Name = ND->getDeclName()) {
+      std::string NameStr = Name.getAsString();
+      Hash = llvm::HashString(NameStr, Hash);
+    }
+    return;
+  }  
+}
+
+class TopLevelDeclTrackerConsumer : public ASTConsumer {
+  ASTUnit &Unit;
+  unsigned &Hash;
+  
+public:
+  TopLevelDeclTrackerConsumer(ASTUnit &_Unit, unsigned &Hash)
+    : Unit(_Unit), Hash(Hash) {
+    Hash = 0;
+  }
+
+  void handleTopLevelDecl(Decl *D) {
+    if (!D)
+      return;
+
+    // FIXME: Currently ObjC method declarations are incorrectly being
+    // reported as top-level declarations, even though their DeclContext
+    // is the containing ObjC @interface/@implementation.  This is a
+    // fundamental problem in the parser right now.
+    if (isa<ObjCMethodDecl>(D))
+      return;
+
+    AddTopLevelDeclarationToHash(D, Hash);
+    Unit.addTopLevelDecl(D);
+
+    handleFileLevelDecl(D);
+  }
+
+  void handleFileLevelDecl(Decl *D) {
+    Unit.addFileLevelDecl(D);
+    if (NamespaceDecl *NSD = dyn_cast<NamespaceDecl>(D)) {
+      for (NamespaceDecl::decl_iterator
+             I = NSD->decls_begin(), E = NSD->decls_end(); I != E; ++I)
+        handleFileLevelDecl(*I);
+    }
+  }
+
+  bool HandleTopLevelDecl(DeclGroupRef D) {
+    for (DeclGroupRef::iterator it = D.begin(), ie = D.end(); it != ie; ++it)
+      handleTopLevelDecl(*it);
+    return true;
+  }
+
+  // We're not interested in "interesting" decls.
+  void HandleInterestingDecl(DeclGroupRef) {}
+
+  void HandleTopLevelDeclInObjCContainer(DeclGroupRef D) {
+    for (DeclGroupRef::iterator it = D.begin(), ie = D.end(); it != ie; ++it)
+      handleTopLevelDecl(*it);
+  }
+};
+
+class TopLevelDeclTrackerAction : public ASTFrontendAction {
+public:
+  ASTUnit &Unit;
+
+  virtual ASTConsumer *CreateASTConsumer(CompilerInstance &CI,
+                                         StringRef InFile) {
+    CI.getPreprocessor().addPPCallbacks(
+     new MacroDefinitionTrackerPPCallbacks(Unit.getCurrentTopLevelHashValue()));
+    return new TopLevelDeclTrackerConsumer(Unit, 
+                                           Unit.getCurrentTopLevelHashValue());
+  }
+
+public:
+  TopLevelDeclTrackerAction(ASTUnit &_Unit) : Unit(_Unit) {}
+
+  virtual bool hasCodeCompletionSupport() const { return false; }
+  virtual TranslationUnitKind getTranslationUnitKind()  { 
+    return Unit.getTranslationUnitKind(); 
+  }
+};
+
+class PrecompilePreambleConsumer : public PCHGenerator {
+  ASTUnit &Unit;
+  unsigned &Hash;                                   
+  std::vector<Decl *> TopLevelDecls;
+                                     
+public:
+  PrecompilePreambleConsumer(ASTUnit &Unit, const Preprocessor &PP, 
+                             StringRef isysroot, raw_ostream *Out)
+    : PCHGenerator(PP, "", 0, isysroot, Out), Unit(Unit),
+      Hash(Unit.getCurrentTopLevelHashValue()) {
+    Hash = 0;
+  }
+
+  virtual bool HandleTopLevelDecl(DeclGroupRef D) {
+    for (DeclGroupRef::iterator it = D.begin(), ie = D.end(); it != ie; ++it) {
+      Decl *D = *it;
+      // FIXME: Currently ObjC method declarations are incorrectly being
+      // reported as top-level declarations, even though their DeclContext
+      // is the containing ObjC @interface/@implementation.  This is a
+      // fundamental problem in the parser right now.
+      if (isa<ObjCMethodDecl>(D))
+        continue;
+      AddTopLevelDeclarationToHash(D, Hash);
+      TopLevelDecls.push_back(D);
+    }
+    return true;
+  }
+
+  virtual void HandleTranslationUnit(ASTContext &Ctx) {
+    PCHGenerator::HandleTranslationUnit(Ctx);
+    if (!Unit.getDiagnostics().hasErrorOccurred()) {
+      // Translate the top-level declarations we captured during
+      // parsing into declaration IDs in the precompiled
+      // preamble. This will allow us to deserialize those top-level
+      // declarations when requested.
+      for (unsigned I = 0, N = TopLevelDecls.size(); I != N; ++I)
+        Unit.addTopLevelDeclFromPreamble(
+                                      getWriter().getDeclID(TopLevelDecls[I]));
+    }
+  }
+};
+
+class PrecompilePreambleAction : public ASTFrontendAction {
+  ASTUnit &Unit;
+
+public:
+  explicit PrecompilePreambleAction(ASTUnit &Unit) : Unit(Unit) {}
+
+  virtual ASTConsumer *CreateASTConsumer(CompilerInstance &CI,
+                                         StringRef InFile) {
+    std::string Sysroot;
+    std::string OutputFile;
+    raw_ostream *OS = 0;
+    if (GeneratePCHAction::ComputeASTConsumerArguments(CI, InFile, Sysroot,
+                                                       OutputFile,
+                                                       OS))
+      return 0;
+    
+    if (!CI.getFrontendOpts().RelocatablePCH)
+      Sysroot.clear();
+
+    CI.getPreprocessor().addPPCallbacks(
+     new MacroDefinitionTrackerPPCallbacks(Unit.getCurrentTopLevelHashValue()));
+    return new PrecompilePreambleConsumer(Unit, CI.getPreprocessor(), Sysroot, 
+                                          OS);
+  }
+
+  virtual bool hasCodeCompletionSupport() const { return false; }
+  virtual bool hasASTFileSupport() const { return false; }
+  virtual TranslationUnitKind getTranslationUnitKind() { return TU_Prefix; }
+};
+
+}
+
+static void checkAndRemoveNonDriverDiags(SmallVectorImpl<StoredDiagnostic> &
+                                                            StoredDiagnostics) {
+  // Get rid of stored diagnostics except the ones from the driver which do not
+  // have a source location.
+  for (unsigned I = 0; I < StoredDiagnostics.size(); ++I) {
+    if (StoredDiagnostics[I].getLocation().isValid()) {
+      StoredDiagnostics.erase(StoredDiagnostics.begin()+I);
+      --I;
+    }
+  }
+}
+
+static void checkAndSanitizeDiags(SmallVectorImpl<StoredDiagnostic> &
+                                                              StoredDiagnostics,
+                                  SourceManager &SM) {
+  // The stored diagnostic has the old source manager in it; update
+  // the locations to refer into the new source manager. Since we've
+  // been careful to make sure that the source manager's state
+  // before and after are identical, so that we can reuse the source
+  // location itself.
+  for (unsigned I = 0, N = StoredDiagnostics.size(); I < N; ++I) {
+    if (StoredDiagnostics[I].getLocation().isValid()) {
+      FullSourceLoc Loc(StoredDiagnostics[I].getLocation(), SM);
+      StoredDiagnostics[I].setLocation(Loc);
+    }
+  }
+}
+
+/// Parse the source file into a translation unit using the given compiler
+/// invocation, replacing the current translation unit.
+///
+/// \returns True if a failure occurred that causes the ASTUnit not to
+/// contain any translation-unit information, false otherwise.
+bool ASTUnit::Parse(llvm::MemoryBuffer *OverrideMainBuffer) {
+  delete SavedMainFileBuffer;
+  SavedMainFileBuffer = 0;
+  
+  if (!Invocation) {
+    delete OverrideMainBuffer;
+    return true;
+  }
+  
+  // Create the compiler instance to use for building the AST.
+  OwningPtr<CompilerInstance> Clang(new CompilerInstance());
+
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance>
+    CICleanup(Clang.get());
+
+  IntrusiveRefCntPtr<CompilerInvocation>
+    CCInvocation(new CompilerInvocation(*Invocation));
+
+  Clang->setInvocation(CCInvocation.getPtr());
+  OriginalSourceFile = Clang->getFrontendOpts().Inputs[0].File;
+    
+  // Set up diagnostics, capturing any diagnostics that would
+  // otherwise be dropped.
+  Clang->setDiagnostics(&getDiagnostics());
+  
+  // Create the target instance.
+  Clang->getTargetOpts().Features = TargetFeatures;
+  Clang->setTarget(TargetInfo::CreateTargetInfo(Clang->getDiagnostics(),
+                   Clang->getTargetOpts()));
+  if (!Clang->hasTarget()) {
+    delete OverrideMainBuffer;
+    return true;
+  }
+
+  // Inform the target of the language options.
+  //
+  // FIXME: We shouldn't need to do this, the target should be immutable once
+  // created. This complexity should be lifted elsewhere.
+  Clang->getTarget().setForcedLangOptions(Clang->getLangOpts());
+  
+  assert(Clang->getFrontendOpts().Inputs.size() == 1 &&
+         "Invocation must have exactly one source file!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_AST &&
+         "FIXME: AST inputs not yet supported here!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_LLVM_IR &&
+         "IR inputs not support here!");
+
+  // Configure the various subsystems.
+  // FIXME: Should we retain the previous file manager?
+  LangOpts = &Clang->getLangOpts();
+  FileSystemOpts = Clang->getFileSystemOpts();
+  FileMgr = new FileManager(FileSystemOpts);
+  SourceMgr = new SourceManager(getDiagnostics(), *FileMgr);
+  TheSema.reset();
+  Ctx = 0;
+  PP = 0;
+  Reader = 0;
+  
+  // Clear out old caches and data.
+  TopLevelDecls.clear();
+  clearFileLevelDecls();
+  CleanTemporaryFiles();
+
+  if (!OverrideMainBuffer) {
+    checkAndRemoveNonDriverDiags(StoredDiagnostics);
+    TopLevelDeclsInPreamble.clear();
+  }
+
+  // Create a file manager object to provide access to and cache the filesystem.
+  Clang->setFileManager(&getFileManager());
+  
+  // Create the source manager.
+  Clang->setSourceManager(&getSourceManager());
+  
+  // If the main file has been overridden due to the use of a preamble,
+  // make that override happen and introduce the preamble.
+  PreprocessorOptions &PreprocessorOpts = Clang->getPreprocessorOpts();
+  if (OverrideMainBuffer) {
+    PreprocessorOpts.addRemappedFile(OriginalSourceFile, OverrideMainBuffer);
+    PreprocessorOpts.PrecompiledPreambleBytes.first = Preamble.size();
+    PreprocessorOpts.PrecompiledPreambleBytes.second
+                                                    = PreambleEndsAtStartOfLine;
+    PreprocessorOpts.ImplicitPCHInclude = getPreambleFile(this);
+    PreprocessorOpts.DisablePCHValidation = true;
+    
+    // The stored diagnostic has the old source manager in it; update
+    // the locations to refer into the new source manager. Since we've
+    // been careful to make sure that the source manager's state
+    // before and after are identical, so that we can reuse the source
+    // location itself.
+    checkAndSanitizeDiags(StoredDiagnostics, getSourceManager());
+
+    // Keep track of the override buffer;
+    SavedMainFileBuffer = OverrideMainBuffer;
+  }
+  
+  OwningPtr<TopLevelDeclTrackerAction> Act(
+    new TopLevelDeclTrackerAction(*this));
+    
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<TopLevelDeclTrackerAction>
+    ActCleanup(Act.get());
+
+  if (!Act->BeginSourceFile(*Clang.get(), Clang->getFrontendOpts().Inputs[0]))
+    goto error;
+
+  if (OverrideMainBuffer) {
+    std::string ModName = getPreambleFile(this);
+    TranslateStoredDiagnostics(Clang->getModuleManager(), ModName,
+                               getSourceManager(), PreambleDiagnostics,
+                               StoredDiagnostics);
+  }
+
+  Act->Execute();
+
+  transferASTDataFromCompilerInstance(*Clang);
+  
+  Act->EndSourceFile();
+
+  FailedParseDiagnostics.clear();
+
+  return false;
+
+error:
+  // Remove the overridden buffer we used for the preamble.
+  if (OverrideMainBuffer) {
+    delete OverrideMainBuffer;
+    SavedMainFileBuffer = 0;
+  }
+
+  // Keep the ownership of the data in the ASTUnit because the client may
+  // want to see the diagnostics.
+  transferASTDataFromCompilerInstance(*Clang);
+  FailedParseDiagnostics.swap(StoredDiagnostics);
+  StoredDiagnostics.clear();
+  NumStoredDiagnosticsFromDriver = 0;
+  return true;
+}
+
+/// \brief Simple function to retrieve a path for a preamble precompiled header.
+static std::string GetPreamblePCHPath() {
+  // FIXME: This is lame; sys::Path should provide this function (in particular,
+  // it should know how to find the temporary files dir).
+  // FIXME: This is really lame. I copied this code from the Driver!
+  // FIXME: This is a hack so that we can override the preamble file during
+  // crash-recovery testing, which is the only case where the preamble files
+  // are not necessarily cleaned up. 
+  const char *TmpFile = ::getenv("CINDEXTEST_PREAMBLE_FILE");
+  if (TmpFile)
+    return TmpFile;
+  
+  std::string Error;
+  const char *TmpDir = ::getenv("TMPDIR");
+  if (!TmpDir)
+    TmpDir = ::getenv("TEMP");
+  if (!TmpDir)
+    TmpDir = ::getenv("TMP");
+#ifdef LLVM_ON_WIN32
+  if (!TmpDir)
+    TmpDir = ::getenv("USERPROFILE");
+#endif
+  if (!TmpDir)
+    TmpDir = "/tmp";
+  llvm::sys::Path P(TmpDir);
+  P.createDirectoryOnDisk(true);
+  P.appendComponent("preamble");
+  P.appendSuffix("pch");
+  if (P.makeUnique(/*reuse_current=*/false, /*ErrMsg*/0))
+    return std::string();
+  
+  return P.str();
+}
+
+/// \brief Compute the preamble for the main file, providing the source buffer
+/// that corresponds to the main file along with a pair (bytes, start-of-line)
+/// that describes the preamble.
+std::pair<llvm::MemoryBuffer *, std::pair<unsigned, bool> > 
+ASTUnit::ComputePreamble(CompilerInvocation &Invocation, 
+                         unsigned MaxLines, bool &CreatedBuffer) {
+  FrontendOptions &FrontendOpts = Invocation.getFrontendOpts();
+  PreprocessorOptions &PreprocessorOpts = Invocation.getPreprocessorOpts();
+  CreatedBuffer = false;
+  
+  // Try to determine if the main file has been remapped, either from the 
+  // command line (to another file) or directly through the compiler invocation
+  // (to a memory buffer).
+  llvm::MemoryBuffer *Buffer = 0;
+  llvm::sys::PathWithStatus MainFilePath(FrontendOpts.Inputs[0].File);
+  if (const llvm::sys::FileStatus *MainFileStatus = MainFilePath.getFileStatus()) {
+    // Check whether there is a file-file remapping of the main file
+    for (PreprocessorOptions::remapped_file_iterator
+          M = PreprocessorOpts.remapped_file_begin(),
+          E = PreprocessorOpts.remapped_file_end();
+         M != E;
+         ++M) {
+      llvm::sys::PathWithStatus MPath(M->first);    
+      if (const llvm::sys::FileStatus *MStatus = MPath.getFileStatus()) {
+        if (MainFileStatus->uniqueID == MStatus->uniqueID) {
+          // We found a remapping. Try to load the resulting, remapped source.
+          if (CreatedBuffer) {
+            delete Buffer;
+            CreatedBuffer = false;
+          }
+          
+          Buffer = getBufferForFile(M->second);
+          if (!Buffer)
+            return std::make_pair((llvm::MemoryBuffer*)0, 
+                                  std::make_pair(0, true));
+          CreatedBuffer = true;
+        }
+      }
+    }
+    
+    // Check whether there is a file-buffer remapping. It supercedes the
+    // file-file remapping.
+    for (PreprocessorOptions::remapped_file_buffer_iterator
+           M = PreprocessorOpts.remapped_file_buffer_begin(),
+           E = PreprocessorOpts.remapped_file_buffer_end();
+         M != E;
+         ++M) {
+      llvm::sys::PathWithStatus MPath(M->first);    
+      if (const llvm::sys::FileStatus *MStatus = MPath.getFileStatus()) {
+        if (MainFileStatus->uniqueID == MStatus->uniqueID) {
+          // We found a remapping. 
+          if (CreatedBuffer) {
+            delete Buffer;
+            CreatedBuffer = false;
+          }
+          
+          Buffer = const_cast<llvm::MemoryBuffer *>(M->second);
+        }
+      }
+    }
+  }
+  
+  // If the main source file was not remapped, load it now.
+  if (!Buffer) {
+    Buffer = getBufferForFile(FrontendOpts.Inputs[0].File);
+    if (!Buffer)
+      return std::make_pair((llvm::MemoryBuffer*)0, std::make_pair(0, true));    
+    
+    CreatedBuffer = true;
+  }
+  
+  return std::make_pair(Buffer, Lexer::ComputePreamble(Buffer,
+                                                       *Invocation.getLangOpts(),
+                                                       MaxLines));
+}
+
+static llvm::MemoryBuffer *CreatePaddedMainFileBuffer(llvm::MemoryBuffer *Old,
+                                                      unsigned NewSize,
+                                                      StringRef NewName) {
+  llvm::MemoryBuffer *Result
+    = llvm::MemoryBuffer::getNewUninitMemBuffer(NewSize, NewName);
+  memcpy(const_cast<char*>(Result->getBufferStart()), 
+         Old->getBufferStart(), Old->getBufferSize());
+  memset(const_cast<char*>(Result->getBufferStart()) + Old->getBufferSize(), 
+         ' ', NewSize - Old->getBufferSize() - 1);
+  const_cast<char*>(Result->getBufferEnd())[-1] = '\n';  
+  
+  return Result;
+}
+
+/// \brief Attempt to build or re-use a precompiled preamble when (re-)parsing
+/// the source file.
+///
+/// This routine will compute the preamble of the main source file. If a
+/// non-trivial preamble is found, it will precompile that preamble into a 
+/// precompiled header so that the precompiled preamble can be used to reduce
+/// reparsing time. If a precompiled preamble has already been constructed,
+/// this routine will determine if it is still valid and, if so, avoid 
+/// rebuilding the precompiled preamble.
+///
+/// \param AllowRebuild When true (the default), this routine is
+/// allowed to rebuild the precompiled preamble if it is found to be
+/// out-of-date.
+///
+/// \param MaxLines When non-zero, the maximum number of lines that
+/// can occur within the preamble.
+///
+/// \returns If the precompiled preamble can be used, returns a newly-allocated
+/// buffer that should be used in place of the main file when doing so.
+/// Otherwise, returns a NULL pointer.
+llvm::MemoryBuffer *ASTUnit::getMainBufferWithPrecompiledPreamble(
+                              const CompilerInvocation &PreambleInvocationIn,
+                                                           bool AllowRebuild,
+                                                           unsigned MaxLines) {
+  
+  IntrusiveRefCntPtr<CompilerInvocation>
+    PreambleInvocation(new CompilerInvocation(PreambleInvocationIn));
+  FrontendOptions &FrontendOpts = PreambleInvocation->getFrontendOpts();
+  PreprocessorOptions &PreprocessorOpts
+    = PreambleInvocation->getPreprocessorOpts();
+
+  bool CreatedPreambleBuffer = false;
+  std::pair<llvm::MemoryBuffer *, std::pair<unsigned, bool> > NewPreamble 
+    = ComputePreamble(*PreambleInvocation, MaxLines, CreatedPreambleBuffer);
+
+  // If ComputePreamble() Take ownership of the preamble buffer.
+  OwningPtr<llvm::MemoryBuffer> OwnedPreambleBuffer;
+  if (CreatedPreambleBuffer)
+    OwnedPreambleBuffer.reset(NewPreamble.first);
+
+  if (!NewPreamble.second.first) {
+    // We couldn't find a preamble in the main source. Clear out the current
+    // preamble, if we have one. It's obviously no good any more.
+    Preamble.clear();
+    erasePreambleFile(this);
+
+    // The next time we actually see a preamble, precompile it.
+    PreambleRebuildCounter = 1;
+    return 0;
+  }
+  
+  if (!Preamble.empty()) {
+    // We've previously computed a preamble. Check whether we have the same
+    // preamble now that we did before, and that there's enough space in
+    // the main-file buffer within the precompiled preamble to fit the
+    // new main file.
+    if (Preamble.size() == NewPreamble.second.first &&
+        PreambleEndsAtStartOfLine == NewPreamble.second.second &&
+        NewPreamble.first->getBufferSize() < PreambleReservedSize-2 &&
+        memcmp(Preamble.getBufferStart(), NewPreamble.first->getBufferStart(),
+               NewPreamble.second.first) == 0) {
+      // The preamble has not changed. We may be able to re-use the precompiled
+      // preamble.
+
+      // Check that none of the files used by the preamble have changed.
+      bool AnyFileChanged = false;
+          
+      // First, make a record of those files that have been overridden via
+      // remapping or unsaved_files.
+      llvm::StringMap<std::pair<off_t, time_t> > OverriddenFiles;
+      for (PreprocessorOptions::remapped_file_iterator
+                R = PreprocessorOpts.remapped_file_begin(),
+             REnd = PreprocessorOpts.remapped_file_end();
+           !AnyFileChanged && R != REnd;
+           ++R) {
+        struct stat StatBuf;
+        if (FileMgr->getNoncachedStatValue(R->second, StatBuf)) {
+          // If we can't stat the file we're remapping to, assume that something
+          // horrible happened.
+          AnyFileChanged = true;
+          break;
+        }
+        
+        OverriddenFiles[R->first] = std::make_pair(StatBuf.st_size, 
+                                                   StatBuf.st_mtime);
+      }
+      for (PreprocessorOptions::remapped_file_buffer_iterator
+                R = PreprocessorOpts.remapped_file_buffer_begin(),
+             REnd = PreprocessorOpts.remapped_file_buffer_end();
+           !AnyFileChanged && R != REnd;
+           ++R) {
+        // FIXME: Should we actually compare the contents of file->buffer
+        // remappings?
+        OverriddenFiles[R->first] = std::make_pair(R->second->getBufferSize(), 
+                                                   0);
+      }
+       
+      // Check whether anything has changed.
+      for (llvm::StringMap<std::pair<off_t, time_t> >::iterator 
+             F = FilesInPreamble.begin(), FEnd = FilesInPreamble.end();
+           !AnyFileChanged && F != FEnd; 
+           ++F) {
+        llvm::StringMap<std::pair<off_t, time_t> >::iterator Overridden
+          = OverriddenFiles.find(F->first());
+        if (Overridden != OverriddenFiles.end()) {
+          // This file was remapped; check whether the newly-mapped file 
+          // matches up with the previous mapping.
+          if (Overridden->second != F->second)
+            AnyFileChanged = true;
+          continue;
+        }
+        
+        // The file was not remapped; check whether it has changed on disk.
+        struct stat StatBuf;
+        if (FileMgr->getNoncachedStatValue(F->first(), StatBuf)) {
+          // If we can't stat the file, assume that something horrible happened.
+          AnyFileChanged = true;
+        } else if (StatBuf.st_size != F->second.first || 
+                   StatBuf.st_mtime != F->second.second)
+          AnyFileChanged = true;
+      }
+          
+      if (!AnyFileChanged) {
+        // Okay! We can re-use the precompiled preamble.
+
+        // Set the state of the diagnostic object to mimic its state
+        // after parsing the preamble.
+        getDiagnostics().Reset();
+        ProcessWarningOptions(getDiagnostics(), 
+                              PreambleInvocation->getDiagnosticOpts());
+        getDiagnostics().setNumWarnings(NumWarningsInPreamble);
+
+        // Create a version of the main file buffer that is padded to
+        // buffer size we reserved when creating the preamble.
+        return CreatePaddedMainFileBuffer(NewPreamble.first, 
+                                          PreambleReservedSize,
+                                          FrontendOpts.Inputs[0].File);
+      }
+    }
+
+    // If we aren't allowed to rebuild the precompiled preamble, just
+    // return now.
+    if (!AllowRebuild)
+      return 0;
+
+    // We can't reuse the previously-computed preamble. Build a new one.
+    Preamble.clear();
+    PreambleDiagnostics.clear();
+    erasePreambleFile(this);
+    PreambleRebuildCounter = 1;
+  } else if (!AllowRebuild) {
+    // We aren't allowed to rebuild the precompiled preamble; just
+    // return now.
+    return 0;
+  }
+
+  // If the preamble rebuild counter > 1, it's because we previously
+  // failed to build a preamble and we're not yet ready to try
+  // again. Decrement the counter and return a failure.
+  if (PreambleRebuildCounter > 1) {
+    --PreambleRebuildCounter;
+    return 0;
+  }
+
+  // Create a temporary file for the precompiled preamble. In rare 
+  // circumstances, this can fail.
+  std::string PreamblePCHPath = GetPreamblePCHPath();
+  if (PreamblePCHPath.empty()) {
+    // Try again next time.
+    PreambleRebuildCounter = 1;
+    return 0;
+  }
+  
+  // We did not previously compute a preamble, or it can't be reused anyway.
+  SimpleTimer PreambleTimer(WantTiming);
+  PreambleTimer.setOutput("Precompiling preamble");
+  
+  // Create a new buffer that stores the preamble. The buffer also contains
+  // extra space for the original contents of the file (which will be present
+  // when we actually parse the file) along with more room in case the file
+  // grows.  
+  PreambleReservedSize = NewPreamble.first->getBufferSize();
+  if (PreambleReservedSize < 4096)
+    PreambleReservedSize = 8191;
+  else
+    PreambleReservedSize *= 2;
+
+  // Save the preamble text for later; we'll need to compare against it for
+  // subsequent reparses.
+  StringRef MainFilename = PreambleInvocation->getFrontendOpts().Inputs[0].File;
+  Preamble.assign(FileMgr->getFile(MainFilename),
+                  NewPreamble.first->getBufferStart(), 
+                  NewPreamble.first->getBufferStart() 
+                                                  + NewPreamble.second.first);
+  PreambleEndsAtStartOfLine = NewPreamble.second.second;
+
+  delete PreambleBuffer;
+  PreambleBuffer
+    = llvm::MemoryBuffer::getNewUninitMemBuffer(PreambleReservedSize,
+                                                FrontendOpts.Inputs[0].File);
+  memcpy(const_cast<char*>(PreambleBuffer->getBufferStart()), 
+         NewPreamble.first->getBufferStart(), Preamble.size());
+  memset(const_cast<char*>(PreambleBuffer->getBufferStart()) + Preamble.size(), 
+         ' ', PreambleReservedSize - Preamble.size() - 1);
+  const_cast<char*>(PreambleBuffer->getBufferEnd())[-1] = '\n';  
+  
+  // Remap the main source file to the preamble buffer.
+  llvm::sys::PathWithStatus MainFilePath(FrontendOpts.Inputs[0].File);
+  PreprocessorOpts.addRemappedFile(MainFilePath.str(), PreambleBuffer);
+  
+  // Tell the compiler invocation to generate a temporary precompiled header.
+  FrontendOpts.ProgramAction = frontend::GeneratePCH;
+  // FIXME: Generate the precompiled header into memory?
+  FrontendOpts.OutputFile = PreamblePCHPath;
+  PreprocessorOpts.PrecompiledPreambleBytes.first = 0;
+  PreprocessorOpts.PrecompiledPreambleBytes.second = false;
+  
+  // Create the compiler instance to use for building the precompiled preamble.
+  OwningPtr<CompilerInstance> Clang(new CompilerInstance());
+
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance>
+    CICleanup(Clang.get());
+
+  Clang->setInvocation(&*PreambleInvocation);
+  OriginalSourceFile = Clang->getFrontendOpts().Inputs[0].File;
+  
+  // Set up diagnostics, capturing all of the diagnostics produced.
+  Clang->setDiagnostics(&getDiagnostics());
+  
+  // Create the target instance.
+  Clang->getTargetOpts().Features = TargetFeatures;
+  Clang->setTarget(TargetInfo::CreateTargetInfo(Clang->getDiagnostics(),
+                                               Clang->getTargetOpts()));
+  if (!Clang->hasTarget()) {
+    llvm::sys::Path(FrontendOpts.OutputFile).eraseFromDisk();
+    Preamble.clear();
+    PreambleRebuildCounter = DefaultPreambleRebuildInterval;
+    PreprocessorOpts.eraseRemappedFile(
+                               PreprocessorOpts.remapped_file_buffer_end() - 1);
+    return 0;
+  }
+  
+  // Inform the target of the language options.
+  //
+  // FIXME: We shouldn't need to do this, the target should be immutable once
+  // created. This complexity should be lifted elsewhere.
+  Clang->getTarget().setForcedLangOptions(Clang->getLangOpts());
+  
+  assert(Clang->getFrontendOpts().Inputs.size() == 1 &&
+         "Invocation must have exactly one source file!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_AST &&
+         "FIXME: AST inputs not yet supported here!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_LLVM_IR &&
+         "IR inputs not support here!");
+  
+  // Clear out old caches and data.
+  getDiagnostics().Reset();
+  ProcessWarningOptions(getDiagnostics(), Clang->getDiagnosticOpts());
+  checkAndRemoveNonDriverDiags(StoredDiagnostics);
+  TopLevelDecls.clear();
+  TopLevelDeclsInPreamble.clear();
+  
+  // Create a file manager object to provide access to and cache the filesystem.
+  Clang->setFileManager(new FileManager(Clang->getFileSystemOpts()));
+  
+  // Create the source manager.
+  Clang->setSourceManager(new SourceManager(getDiagnostics(),
+                                            Clang->getFileManager()));
+  
+  OwningPtr<PrecompilePreambleAction> Act;
+  Act.reset(new PrecompilePreambleAction(*this));
+  if (!Act->BeginSourceFile(*Clang.get(), Clang->getFrontendOpts().Inputs[0])) {
+    llvm::sys::Path(FrontendOpts.OutputFile).eraseFromDisk();
+    Preamble.clear();
+    PreambleRebuildCounter = DefaultPreambleRebuildInterval;
+    PreprocessorOpts.eraseRemappedFile(
+                               PreprocessorOpts.remapped_file_buffer_end() - 1);
+    return 0;
+  }
+  
+  Act->Execute();
+  Act->EndSourceFile();
+
+  if (Diagnostics->hasErrorOccurred()) {
+    // There were errors parsing the preamble, so no precompiled header was
+    // generated. Forget that we even tried.
+    // FIXME: Should we leave a note for ourselves to try again?
+    llvm::sys::Path(FrontendOpts.OutputFile).eraseFromDisk();
+    Preamble.clear();
+    TopLevelDeclsInPreamble.clear();
+    PreambleRebuildCounter = DefaultPreambleRebuildInterval;
+    PreprocessorOpts.eraseRemappedFile(
+                               PreprocessorOpts.remapped_file_buffer_end() - 1);
+    return 0;
+  }
+  
+  // Transfer any diagnostics generated when parsing the preamble into the set
+  // of preamble diagnostics.
+  PreambleDiagnostics.clear();
+  PreambleDiagnostics.insert(PreambleDiagnostics.end(), 
+                            stored_diag_afterDriver_begin(), stored_diag_end());
+  checkAndRemoveNonDriverDiags(StoredDiagnostics);
+  
+  // Keep track of the preamble we precompiled.
+  setPreambleFile(this, FrontendOpts.OutputFile);
+  NumWarningsInPreamble = getDiagnostics().getNumWarnings();
+  
+  // Keep track of all of the files that the source manager knows about,
+  // so we can verify whether they have changed or not.
+  FilesInPreamble.clear();
+  SourceManager &SourceMgr = Clang->getSourceManager();
+  const llvm::MemoryBuffer *MainFileBuffer
+    = SourceMgr.getBuffer(SourceMgr.getMainFileID());
+  for (SourceManager::fileinfo_iterator F = SourceMgr.fileinfo_begin(),
+                                     FEnd = SourceMgr.fileinfo_end();
+       F != FEnd;
+       ++F) {
+    const FileEntry *File = F->second->OrigEntry;
+    if (!File || F->second->getRawBuffer() == MainFileBuffer)
+      continue;
+    
+    FilesInPreamble[File->getName()]
+      = std::make_pair(F->second->getSize(), File->getModificationTime());
+  }
+  
+  PreambleRebuildCounter = 1;
+  PreprocessorOpts.eraseRemappedFile(
+                               PreprocessorOpts.remapped_file_buffer_end() - 1);
+  
+  // If the hash of top-level entities differs from the hash of the top-level
+  // entities the last time we rebuilt the preamble, clear out the completion
+  // cache.
+  if (CurrentTopLevelHashValue != PreambleTopLevelHashValue) {
+    CompletionCacheTopLevelHashValue = 0;
+    PreambleTopLevelHashValue = CurrentTopLevelHashValue;
+  }
+  
+  return CreatePaddedMainFileBuffer(NewPreamble.first, 
+                                    PreambleReservedSize,
+                                    FrontendOpts.Inputs[0].File);
+}
+
+void ASTUnit::RealizeTopLevelDeclsFromPreamble() {
+  std::vector<Decl *> Resolved;
+  Resolved.reserve(TopLevelDeclsInPreamble.size());
+  ExternalASTSource &Source = *getASTContext().getExternalSource();
+  for (unsigned I = 0, N = TopLevelDeclsInPreamble.size(); I != N; ++I) {
+    // Resolve the declaration ID to an actual declaration, possibly
+    // deserializing the declaration in the process.
+    Decl *D = Source.GetExternalDecl(TopLevelDeclsInPreamble[I]);
+    if (D)
+      Resolved.push_back(D);
+  }
+  TopLevelDeclsInPreamble.clear();
+  TopLevelDecls.insert(TopLevelDecls.begin(), Resolved.begin(), Resolved.end());
+}
+
+void ASTUnit::transferASTDataFromCompilerInstance(CompilerInstance &CI) {
+  // Steal the created target, context, and preprocessor.
+  TheSema.reset(CI.takeSema());
+  Consumer.reset(CI.takeASTConsumer());
+  Ctx = &CI.getASTContext();
+  PP = &CI.getPreprocessor();
+  CI.setSourceManager(0);
+  CI.setFileManager(0);
+  Target = &CI.getTarget();
+  Reader = CI.getModuleManager();
+}
+
+StringRef ASTUnit::getMainFileName() const {
+  return Invocation->getFrontendOpts().Inputs[0].File;
+}
+
+ASTUnit *ASTUnit::create(CompilerInvocation *CI,
+                         IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+                         bool CaptureDiagnostics) {
+  OwningPtr<ASTUnit> AST;
+  AST.reset(new ASTUnit(false));
+  ConfigureDiags(Diags, 0, 0, *AST, CaptureDiagnostics);
+  AST->Diagnostics = Diags;
+  AST->Invocation = CI;
+  AST->FileSystemOpts = CI->getFileSystemOpts();
+  AST->FileMgr = new FileManager(AST->FileSystemOpts);
+  AST->SourceMgr = new SourceManager(AST->getDiagnostics(), *AST->FileMgr);
+
+  return AST.take();
+}
+
+ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(CompilerInvocation *CI,
+                              IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+                                             ASTFrontendAction *Action,
+                                             ASTUnit *Unit,
+                                             bool Persistent,
+                                             StringRef ResourceFilesPath,
+                                             bool OnlyLocalDecls,
+                                             bool CaptureDiagnostics,
+                                             bool PrecompilePreamble,
+                                             bool CacheCodeCompletionResults,
+                                             OwningPtr<ASTUnit> *ErrAST) {
+  assert(CI && "A CompilerInvocation is required");
+
+  OwningPtr<ASTUnit> OwnAST;
+  ASTUnit *AST = Unit;
+  if (!AST) {
+    // Create the AST unit.
+    OwnAST.reset(create(CI, Diags, CaptureDiagnostics));
+    AST = OwnAST.get();
+  }
+  
+  if (!ResourceFilesPath.empty()) {
+    // Override the resources path.
+    CI->getHeaderSearchOpts().ResourceDir = ResourceFilesPath;
+  }
+  AST->OnlyLocalDecls = OnlyLocalDecls;
+  AST->CaptureDiagnostics = CaptureDiagnostics;
+  if (PrecompilePreamble)
+    AST->PreambleRebuildCounter = 2;
+  AST->TUKind = Action ? Action->getTranslationUnitKind() : TU_Complete;
+  AST->ShouldCacheCodeCompletionResults = CacheCodeCompletionResults;
+
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<ASTUnit>
+    ASTUnitCleanup(OwnAST.get());
+  llvm::CrashRecoveryContextCleanupRegistrar<DiagnosticsEngine,
+    llvm::CrashRecoveryContextReleaseRefCleanup<DiagnosticsEngine> >
+    DiagCleanup(Diags.getPtr());
+
+  // We'll manage file buffers ourselves.
+  CI->getPreprocessorOpts().RetainRemappedFileBuffers = true;
+  CI->getFrontendOpts().DisableFree = false;
+  ProcessWarningOptions(AST->getDiagnostics(), CI->getDiagnosticOpts());
+
+  // Save the target features.
+  AST->TargetFeatures = CI->getTargetOpts().Features;
+
+  // Create the compiler instance to use for building the AST.
+  OwningPtr<CompilerInstance> Clang(new CompilerInstance());
+
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance>
+    CICleanup(Clang.get());
+
+  Clang->setInvocation(CI);
+  AST->OriginalSourceFile = Clang->getFrontendOpts().Inputs[0].File;
+    
+  // Set up diagnostics, capturing any diagnostics that would
+  // otherwise be dropped.
+  Clang->setDiagnostics(&AST->getDiagnostics());
+  
+  // Create the target instance.
+  Clang->getTargetOpts().Features = AST->TargetFeatures;
+  Clang->setTarget(TargetInfo::CreateTargetInfo(Clang->getDiagnostics(),
+                   Clang->getTargetOpts()));
+  if (!Clang->hasTarget())
+    return 0;
+
+  // Inform the target of the language options.
+  //
+  // FIXME: We shouldn't need to do this, the target should be immutable once
+  // created. This complexity should be lifted elsewhere.
+  Clang->getTarget().setForcedLangOptions(Clang->getLangOpts());
+  
+  assert(Clang->getFrontendOpts().Inputs.size() == 1 &&
+         "Invocation must have exactly one source file!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_AST &&
+         "FIXME: AST inputs not yet supported here!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_LLVM_IR &&
+         "IR inputs not supported here!");
+
+  // Configure the various subsystems.
+  AST->TheSema.reset();
+  AST->Ctx = 0;
+  AST->PP = 0;
+  AST->Reader = 0;
+  
+  // Create a file manager object to provide access to and cache the filesystem.
+  Clang->setFileManager(&AST->getFileManager());
+  
+  // Create the source manager.
+  Clang->setSourceManager(&AST->getSourceManager());
+
+  ASTFrontendAction *Act = Action;
+
+  OwningPtr<TopLevelDeclTrackerAction> TrackerAct;
+  if (!Act) {
+    TrackerAct.reset(new TopLevelDeclTrackerAction(*AST));
+    Act = TrackerAct.get();
+  }
+
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<TopLevelDeclTrackerAction>
+    ActCleanup(TrackerAct.get());
+
+  if (!Act->BeginSourceFile(*Clang.get(), Clang->getFrontendOpts().Inputs[0])) {
+    AST->transferASTDataFromCompilerInstance(*Clang);
+    if (OwnAST && ErrAST)
+      ErrAST->swap(OwnAST);
+
+    return 0;
+  }
+
+  if (Persistent && !TrackerAct) {
+    Clang->getPreprocessor().addPPCallbacks(
+     new MacroDefinitionTrackerPPCallbacks(AST->getCurrentTopLevelHashValue()));
+    std::vector<ASTConsumer*> Consumers;
+    if (Clang->hasASTConsumer())
+      Consumers.push_back(Clang->takeASTConsumer());
+    Consumers.push_back(new TopLevelDeclTrackerConsumer(*AST,
+                                           AST->getCurrentTopLevelHashValue()));
+    Clang->setASTConsumer(new MultiplexConsumer(Consumers));
+  }
+  Act->Execute();
+
+  // Steal the created target, context, and preprocessor.
+  AST->transferASTDataFromCompilerInstance(*Clang);
+  
+  Act->EndSourceFile();
+
+  if (OwnAST)
+    return OwnAST.take();
+  else
+    return AST;
+}
+
+bool ASTUnit::LoadFromCompilerInvocation(bool PrecompilePreamble) {
+  if (!Invocation)
+    return true;
+  
+  // We'll manage file buffers ourselves.
+  Invocation->getPreprocessorOpts().RetainRemappedFileBuffers = true;
+  Invocation->getFrontendOpts().DisableFree = false;
+  ProcessWarningOptions(getDiagnostics(), Invocation->getDiagnosticOpts());
+
+  // Save the target features.
+  TargetFeatures = Invocation->getTargetOpts().Features;
+  
+  llvm::MemoryBuffer *OverrideMainBuffer = 0;
+  if (PrecompilePreamble) {
+    PreambleRebuildCounter = 2;
+    OverrideMainBuffer
+      = getMainBufferWithPrecompiledPreamble(*Invocation);
+  }
+  
+  SimpleTimer ParsingTimer(WantTiming);
+  ParsingTimer.setOutput("Parsing " + getMainFileName());
+  
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<llvm::MemoryBuffer>
+    MemBufferCleanup(OverrideMainBuffer);
+  
+  return Parse(OverrideMainBuffer);
+}
+
+ASTUnit *ASTUnit::LoadFromCompilerInvocation(CompilerInvocation *CI,
+                              IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+                                             bool OnlyLocalDecls,
+                                             bool CaptureDiagnostics,
+                                             bool PrecompilePreamble,
+                                             TranslationUnitKind TUKind,
+                                             bool CacheCodeCompletionResults) {  
+  // Create the AST unit.
+  OwningPtr<ASTUnit> AST;
+  AST.reset(new ASTUnit(false));
+  ConfigureDiags(Diags, 0, 0, *AST, CaptureDiagnostics);
+  AST->Diagnostics = Diags;
+  AST->OnlyLocalDecls = OnlyLocalDecls;
+  AST->CaptureDiagnostics = CaptureDiagnostics;
+  AST->TUKind = TUKind;
+  AST->ShouldCacheCodeCompletionResults = CacheCodeCompletionResults;
+  AST->Invocation = CI;
+  
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<ASTUnit>
+    ASTUnitCleanup(AST.get());
+  llvm::CrashRecoveryContextCleanupRegistrar<DiagnosticsEngine,
+    llvm::CrashRecoveryContextReleaseRefCleanup<DiagnosticsEngine> >
+    DiagCleanup(Diags.getPtr());
+
+  return AST->LoadFromCompilerInvocation(PrecompilePreamble)? 0 : AST.take();
+}
+
+ASTUnit *ASTUnit::LoadFromCommandLine(const char **ArgBegin,
+                                      const char **ArgEnd,
+                                    IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+                                      StringRef ResourceFilesPath,
+                                      bool OnlyLocalDecls,
+                                      bool CaptureDiagnostics,
+                                      RemappedFile *RemappedFiles,
+                                      unsigned NumRemappedFiles,
+                                      bool RemappedFilesKeepOriginalName,
+                                      bool PrecompilePreamble,
+                                      TranslationUnitKind TUKind,
+                                      bool CacheCodeCompletionResults,
+                                      bool AllowPCHWithCompilerErrors,
+                                      bool SkipFunctionBodies,
+                                      OwningPtr<ASTUnit> *ErrAST) {
+  if (!Diags.getPtr()) {
+    // No diagnostics engine was provided, so create our own diagnostics object
+    // with the default options.
+    DiagnosticOptions DiagOpts;
+    Diags = CompilerInstance::createDiagnostics(DiagOpts, ArgEnd - ArgBegin, 
+                                                ArgBegin);
+  }
+
+  SmallVector<StoredDiagnostic, 4> StoredDiagnostics;
+  
+  IntrusiveRefCntPtr<CompilerInvocation> CI;
+
+  {
+
+    CaptureDroppedDiagnostics Capture(CaptureDiagnostics, *Diags, 
+                                      StoredDiagnostics);
+
+    CI = clang::createInvocationFromCommandLine(
+                                           llvm::makeArrayRef(ArgBegin, ArgEnd),
+                                           Diags);
+    if (!CI)
+      return 0;
+  }
+
+  // Override any files that need remapping
+  for (unsigned I = 0; I != NumRemappedFiles; ++I) {
+    FilenameOrMemBuf fileOrBuf = RemappedFiles[I].second;
+    if (const llvm::MemoryBuffer *
+            memBuf = fileOrBuf.dyn_cast<const llvm::MemoryBuffer *>()) {
+      CI->getPreprocessorOpts().addRemappedFile(RemappedFiles[I].first, memBuf);
+    } else {
+      const char *fname = fileOrBuf.get<const char *>();
+      CI->getPreprocessorOpts().addRemappedFile(RemappedFiles[I].first, fname);
+    }
+  }
+  PreprocessorOptions &PPOpts = CI->getPreprocessorOpts();
+  PPOpts.RemappedFilesKeepOriginalName = RemappedFilesKeepOriginalName;
+  PPOpts.AllowPCHWithCompilerErrors = AllowPCHWithCompilerErrors;
+  
+  // Override the resources path.
+  CI->getHeaderSearchOpts().ResourceDir = ResourceFilesPath;
+
+  CI->getFrontendOpts().SkipFunctionBodies = SkipFunctionBodies;
+
+  // Create the AST unit.
+  OwningPtr<ASTUnit> AST;
+  AST.reset(new ASTUnit(false));
+  ConfigureDiags(Diags, ArgBegin, ArgEnd, *AST, CaptureDiagnostics);
+  AST->Diagnostics = Diags;
+  Diags = 0; // Zero out now to ease cleanup during crash recovery.
+  AST->FileSystemOpts = CI->getFileSystemOpts();
+  AST->FileMgr = new FileManager(AST->FileSystemOpts);
+  AST->OnlyLocalDecls = OnlyLocalDecls;
+  AST->CaptureDiagnostics = CaptureDiagnostics;
+  AST->TUKind = TUKind;
+  AST->ShouldCacheCodeCompletionResults = CacheCodeCompletionResults;
+  AST->NumStoredDiagnosticsFromDriver = StoredDiagnostics.size();
+  AST->StoredDiagnostics.swap(StoredDiagnostics);
+  AST->Invocation = CI;
+  CI = 0; // Zero out now to ease cleanup during crash recovery.
+  
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<ASTUnit>
+    ASTUnitCleanup(AST.get());
+
+  if (AST->LoadFromCompilerInvocation(PrecompilePreamble)) {
+    // Some error occurred, if caller wants to examine diagnostics, pass it the
+    // ASTUnit.
+    if (ErrAST) {
+      AST->StoredDiagnostics.swap(AST->FailedParseDiagnostics);
+      ErrAST->swap(AST);
+    }
+    return 0;
+  }
+
+  return AST.take();
+}
+
+bool ASTUnit::Reparse(RemappedFile *RemappedFiles, unsigned NumRemappedFiles) {
+  if (!Invocation)
+    return true;
+
+  clearFileLevelDecls();
+  
+  SimpleTimer ParsingTimer(WantTiming);
+  ParsingTimer.setOutput("Reparsing " + getMainFileName());
+
+  // Remap files.
+  PreprocessorOptions &PPOpts = Invocation->getPreprocessorOpts();
+  PPOpts.DisableStatCache = true;
+  for (PreprocessorOptions::remapped_file_buffer_iterator 
+         R = PPOpts.remapped_file_buffer_begin(),
+         REnd = PPOpts.remapped_file_buffer_end();
+       R != REnd; 
+       ++R) {
+    delete R->second;
+  }
+  Invocation->getPreprocessorOpts().clearRemappedFiles();
+  for (unsigned I = 0; I != NumRemappedFiles; ++I) {
+    FilenameOrMemBuf fileOrBuf = RemappedFiles[I].second;
+    if (const llvm::MemoryBuffer *
+            memBuf = fileOrBuf.dyn_cast<const llvm::MemoryBuffer *>()) {
+      Invocation->getPreprocessorOpts().addRemappedFile(RemappedFiles[I].first,
+                                                        memBuf);
+    } else {
+      const char *fname = fileOrBuf.get<const char *>();
+      Invocation->getPreprocessorOpts().addRemappedFile(RemappedFiles[I].first,
+                                                        fname);
+    }
+  }
+  
+  // If we have a preamble file lying around, or if we might try to
+  // build a precompiled preamble, do so now.
+  llvm::MemoryBuffer *OverrideMainBuffer = 0;
+  if (!getPreambleFile(this).empty() || PreambleRebuildCounter > 0)
+    OverrideMainBuffer = getMainBufferWithPrecompiledPreamble(*Invocation);
+    
+  // Clear out the diagnostics state.
+  getDiagnostics().Reset();
+  ProcessWarningOptions(getDiagnostics(), Invocation->getDiagnosticOpts());
+  if (OverrideMainBuffer)
+    getDiagnostics().setNumWarnings(NumWarningsInPreamble);
+
+  // Parse the sources
+  bool Result = Parse(OverrideMainBuffer);
+  
+  // If we're caching global code-completion results, and the top-level 
+  // declarations have changed, clear out the code-completion cache.
+  if (!Result && ShouldCacheCodeCompletionResults &&
+      CurrentTopLevelHashValue != CompletionCacheTopLevelHashValue)
+    CacheCodeCompletionResults();
+
+  // We now need to clear out the completion info related to this translation
+  // unit; it'll be recreated if necessary.
+  CCTUInfo.reset();
+  
+  return Result;
+}
+
+//----------------------------------------------------------------------------//
+// Code completion
+//----------------------------------------------------------------------------//
+
+namespace {
+  /// \brief Code completion consumer that combines the cached code-completion
+  /// results from an ASTUnit with the code-completion results provided to it,
+  /// then passes the result on to 
+  class AugmentedCodeCompleteConsumer : public CodeCompleteConsumer {
+    unsigned long long NormalContexts;
+    ASTUnit &AST;
+    CodeCompleteConsumer &Next;
+    
+  public:
+    AugmentedCodeCompleteConsumer(ASTUnit &AST, CodeCompleteConsumer &Next,
+                                  bool IncludeMacros, bool IncludeCodePatterns,
+                                  bool IncludeGlobals)
+      : CodeCompleteConsumer(IncludeMacros, IncludeCodePatterns, IncludeGlobals,
+                             Next.isOutputBinary()), AST(AST), Next(Next) 
+    { 
+      // Compute the set of contexts in which we will look when we don't have
+      // any information about the specific context.
+      NormalContexts 
+        = (1LL << (CodeCompletionContext::CCC_TopLevel - 1))
+        | (1LL << (CodeCompletionContext::CCC_ObjCInterface - 1))
+        | (1LL << (CodeCompletionContext::CCC_ObjCImplementation - 1))
+        | (1LL << (CodeCompletionContext::CCC_ObjCIvarList - 1))
+        | (1LL << (CodeCompletionContext::CCC_Statement - 1))
+        | (1LL << (CodeCompletionContext::CCC_Expression - 1))
+        | (1LL << (CodeCompletionContext::CCC_ObjCMessageReceiver - 1))
+        | (1LL << (CodeCompletionContext::CCC_DotMemberAccess - 1))
+        | (1LL << (CodeCompletionContext::CCC_ArrowMemberAccess - 1))
+        | (1LL << (CodeCompletionContext::CCC_ObjCPropertyAccess - 1))
+        | (1LL << (CodeCompletionContext::CCC_ObjCProtocolName - 1))
+        | (1LL << (CodeCompletionContext::CCC_ParenthesizedExpression - 1))
+        | (1LL << (CodeCompletionContext::CCC_Recovery - 1));
+
+      if (AST.getASTContext().getLangOpts().CPlusPlus)
+        NormalContexts |= (1LL << (CodeCompletionContext::CCC_EnumTag - 1))
+                   | (1LL << (CodeCompletionContext::CCC_UnionTag - 1))
+                   | (1LL << (CodeCompletionContext::CCC_ClassOrStructTag - 1));
+    }
+    
+    virtual void ProcessCodeCompleteResults(Sema &S, 
+                                            CodeCompletionContext Context,
+                                            CodeCompletionResult *Results,
+                                            unsigned NumResults);
+    
+    virtual void ProcessOverloadCandidates(Sema &S, unsigned CurrentArg,
+                                           OverloadCandidate *Candidates,
+                                           unsigned NumCandidates) { 
+      Next.ProcessOverloadCandidates(S, CurrentArg, Candidates, NumCandidates);
+    }
+    
+    virtual CodeCompletionAllocator &getAllocator() {
+      return Next.getAllocator();
+    }
+
+    virtual CodeCompletionTUInfo &getCodeCompletionTUInfo() {
+      return Next.getCodeCompletionTUInfo();
+    }
+  };
+}
+
+/// \brief Helper function that computes which global names are hidden by the
+/// local code-completion results.
+static void CalculateHiddenNames(const CodeCompletionContext &Context,
+                                 CodeCompletionResult *Results,
+                                 unsigned NumResults,
+                                 ASTContext &Ctx,
+                          llvm::StringSet<llvm::BumpPtrAllocator> &HiddenNames){
+  bool OnlyTagNames = false;
+  switch (Context.getKind()) {
+  case CodeCompletionContext::CCC_Recovery:
+  case CodeCompletionContext::CCC_TopLevel:
+  case CodeCompletionContext::CCC_ObjCInterface:
+  case CodeCompletionContext::CCC_ObjCImplementation:
+  case CodeCompletionContext::CCC_ObjCIvarList:
+  case CodeCompletionContext::CCC_ClassStructUnion:
+  case CodeCompletionContext::CCC_Statement:
+  case CodeCompletionContext::CCC_Expression:
+  case CodeCompletionContext::CCC_ObjCMessageReceiver:
+  case CodeCompletionContext::CCC_DotMemberAccess:
+  case CodeCompletionContext::CCC_ArrowMemberAccess:
+  case CodeCompletionContext::CCC_ObjCPropertyAccess:
+  case CodeCompletionContext::CCC_Namespace:
+  case CodeCompletionContext::CCC_Type:
+  case CodeCompletionContext::CCC_Name:
+  case CodeCompletionContext::CCC_PotentiallyQualifiedName:
+  case CodeCompletionContext::CCC_ParenthesizedExpression:
+  case CodeCompletionContext::CCC_ObjCInterfaceName:
+    break;
+    
+  case CodeCompletionContext::CCC_EnumTag:
+  case CodeCompletionContext::CCC_UnionTag:
+  case CodeCompletionContext::CCC_ClassOrStructTag:
+    OnlyTagNames = true;
+    break;
+    
+  case CodeCompletionContext::CCC_ObjCProtocolName:
+  case CodeCompletionContext::CCC_MacroName:
+  case CodeCompletionContext::CCC_MacroNameUse:
+  case CodeCompletionContext::CCC_PreprocessorExpression:
+  case CodeCompletionContext::CCC_PreprocessorDirective:
+  case CodeCompletionContext::CCC_NaturalLanguage:
+  case CodeCompletionContext::CCC_SelectorName:
+  case CodeCompletionContext::CCC_TypeQualifiers:
+  case CodeCompletionContext::CCC_Other:
+  case CodeCompletionContext::CCC_OtherWithMacros:
+  case CodeCompletionContext::CCC_ObjCInstanceMessage:
+  case CodeCompletionContext::CCC_ObjCClassMessage:
+  case CodeCompletionContext::CCC_ObjCCategoryName:
+    // We're looking for nothing, or we're looking for names that cannot
+    // be hidden.
+    return;
+  }
+  
+  typedef CodeCompletionResult Result;
+  for (unsigned I = 0; I != NumResults; ++I) {
+    if (Results[I].Kind != Result::RK_Declaration)
+      continue;
+    
+    unsigned IDNS
+      = Results[I].Declaration->getUnderlyingDecl()->getIdentifierNamespace();
+
+    bool Hiding = false;
+    if (OnlyTagNames)
+      Hiding = (IDNS & Decl::IDNS_Tag);
+    else {
+      unsigned HiddenIDNS = (Decl::IDNS_Type | Decl::IDNS_Member | 
+                             Decl::IDNS_Namespace | Decl::IDNS_Ordinary |
+                             Decl::IDNS_NonMemberOperator);
+      if (Ctx.getLangOpts().CPlusPlus)
+        HiddenIDNS |= Decl::IDNS_Tag;
+      Hiding = (IDNS & HiddenIDNS);
+    }
+  
+    if (!Hiding)
+      continue;
+    
+    DeclarationName Name = Results[I].Declaration->getDeclName();
+    if (IdentifierInfo *Identifier = Name.getAsIdentifierInfo())
+      HiddenNames.insert(Identifier->getName());
+    else
+      HiddenNames.insert(Name.getAsString());
+  }
+}
+
+
+void AugmentedCodeCompleteConsumer::ProcessCodeCompleteResults(Sema &S,
+                                            CodeCompletionContext Context,
+                                            CodeCompletionResult *Results,
+                                            unsigned NumResults) { 
+  // Merge the results we were given with the results we cached.
+  bool AddedResult = false;
+  unsigned InContexts  
+    = (Context.getKind() == CodeCompletionContext::CCC_Recovery? NormalContexts
+                                        : (1ULL << (Context.getKind() - 1)));
+  // Contains the set of names that are hidden by "local" completion results.
+  llvm::StringSet<llvm::BumpPtrAllocator> HiddenNames;
+  typedef CodeCompletionResult Result;
+  SmallVector<Result, 8> AllResults;
+  for (ASTUnit::cached_completion_iterator 
+            C = AST.cached_completion_begin(),
+         CEnd = AST.cached_completion_end();
+       C != CEnd; ++C) {
+    // If the context we are in matches any of the contexts we are 
+    // interested in, we'll add this result.
+    if ((C->ShowInContexts & InContexts) == 0)
+      continue;
+    
+    // If we haven't added any results previously, do so now.
+    if (!AddedResult) {
+      CalculateHiddenNames(Context, Results, NumResults, S.Context, 
+                           HiddenNames);
+      AllResults.insert(AllResults.end(), Results, Results + NumResults);
+      AddedResult = true;
+    }
+    
+    // Determine whether this global completion result is hidden by a local
+    // completion result. If so, skip it.
+    if (C->Kind != CXCursor_MacroDefinition &&
+        HiddenNames.count(C->Completion->getTypedText()))
+      continue;
+    
+    // Adjust priority based on similar type classes.
+    unsigned Priority = C->Priority;
+    CXCursorKind CursorKind = C->Kind;
+    CodeCompletionString *Completion = C->Completion;
+    if (!Context.getPreferredType().isNull()) {
+      if (C->Kind == CXCursor_MacroDefinition) {
+        Priority = getMacroUsagePriority(C->Completion->getTypedText(),
+                                         S.getLangOpts(),
+                               Context.getPreferredType()->isAnyPointerType());        
+      } else if (C->Type) {
+        CanQualType Expected
+          = S.Context.getCanonicalType(
+                               Context.getPreferredType().getUnqualifiedType());
+        SimplifiedTypeClass ExpectedSTC = getSimplifiedTypeClass(Expected);
+        if (ExpectedSTC == C->TypeClass) {
+          // We know this type is similar; check for an exact match.
+          llvm::StringMap<unsigned> &CachedCompletionTypes
+            = AST.getCachedCompletionTypes();
+          llvm::StringMap<unsigned>::iterator Pos
+            = CachedCompletionTypes.find(QualType(Expected).getAsString());
+          if (Pos != CachedCompletionTypes.end() && Pos->second == C->Type)
+            Priority /= CCF_ExactTypeMatch;
+          else
+            Priority /= CCF_SimilarTypeMatch;
+        }
+      }
+    }
+    
+    // Adjust the completion string, if required.
+    if (C->Kind == CXCursor_MacroDefinition &&
+        Context.getKind() == CodeCompletionContext::CCC_MacroNameUse) {
+      // Create a new code-completion string that just contains the
+      // macro name, without its arguments.
+      CodeCompletionBuilder Builder(getAllocator(), getCodeCompletionTUInfo(),
+                                    CCP_CodePattern, C->Availability);
+      Builder.AddTypedTextChunk(C->Completion->getTypedText());
+      CursorKind = CXCursor_NotImplemented;
+      Priority = CCP_CodePattern;
+      Completion = Builder.TakeString();
+    }
+    
+    AllResults.push_back(Result(Completion, Priority, CursorKind, 
+                                C->Availability));
+  }
+  
+  // If we did not add any cached completion results, just forward the
+  // results we were given to the next consumer.
+  if (!AddedResult) {
+    Next.ProcessCodeCompleteResults(S, Context, Results, NumResults);
+    return;
+  }
+  
+  Next.ProcessCodeCompleteResults(S, Context, AllResults.data(),
+                                  AllResults.size());
+}
+
+
+
+void ASTUnit::CodeComplete(StringRef File, unsigned Line, unsigned Column,
+                           RemappedFile *RemappedFiles, 
+                           unsigned NumRemappedFiles,
+                           bool IncludeMacros, 
+                           bool IncludeCodePatterns,
+                           CodeCompleteConsumer &Consumer,
+                           DiagnosticsEngine &Diag, LangOptions &LangOpts,
+                           SourceManager &SourceMgr, FileManager &FileMgr,
+                   SmallVectorImpl<StoredDiagnostic> &StoredDiagnostics,
+             SmallVectorImpl<const llvm::MemoryBuffer *> &OwnedBuffers) {
+  if (!Invocation)
+    return;
+
+  SimpleTimer CompletionTimer(WantTiming);
+  CompletionTimer.setOutput("Code completion @ " + File + ":" +
+                            Twine(Line) + ":" + Twine(Column));
+
+  IntrusiveRefCntPtr<CompilerInvocation>
+    CCInvocation(new CompilerInvocation(*Invocation));
+
+  FrontendOptions &FrontendOpts = CCInvocation->getFrontendOpts();
+  PreprocessorOptions &PreprocessorOpts = CCInvocation->getPreprocessorOpts();
+
+  FrontendOpts.ShowMacrosInCodeCompletion
+    = IncludeMacros && CachedCompletionResults.empty();
+  FrontendOpts.ShowCodePatternsInCodeCompletion = IncludeCodePatterns;
+  FrontendOpts.ShowGlobalSymbolsInCodeCompletion
+    = CachedCompletionResults.empty();
+  FrontendOpts.CodeCompletionAt.FileName = File;
+  FrontendOpts.CodeCompletionAt.Line = Line;
+  FrontendOpts.CodeCompletionAt.Column = Column;
+
+  // Set the language options appropriately.
+  LangOpts = *CCInvocation->getLangOpts();
+
+  OwningPtr<CompilerInstance> Clang(new CompilerInstance());
+
+  // Recover resources if we crash before exiting this method.
+  llvm::CrashRecoveryContextCleanupRegistrar<CompilerInstance>
+    CICleanup(Clang.get());
+
+  Clang->setInvocation(&*CCInvocation);
+  OriginalSourceFile = Clang->getFrontendOpts().Inputs[0].File;
+    
+  // Set up diagnostics, capturing any diagnostics produced.
+  Clang->setDiagnostics(&Diag);
+  ProcessWarningOptions(Diag, CCInvocation->getDiagnosticOpts());
+  CaptureDroppedDiagnostics Capture(true, 
+                                    Clang->getDiagnostics(), 
+                                    StoredDiagnostics);
+  
+  // Create the target instance.
+  Clang->getTargetOpts().Features = TargetFeatures;
+  Clang->setTarget(TargetInfo::CreateTargetInfo(Clang->getDiagnostics(),
+                                               Clang->getTargetOpts()));
+  if (!Clang->hasTarget()) {
+    Clang->setInvocation(0);
+    return;
+  }
+  
+  // Inform the target of the language options.
+  //
+  // FIXME: We shouldn't need to do this, the target should be immutable once
+  // created. This complexity should be lifted elsewhere.
+  Clang->getTarget().setForcedLangOptions(Clang->getLangOpts());
+  
+  assert(Clang->getFrontendOpts().Inputs.size() == 1 &&
+         "Invocation must have exactly one source file!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_AST &&
+         "FIXME: AST inputs not yet supported here!");
+  assert(Clang->getFrontendOpts().Inputs[0].Kind != IK_LLVM_IR &&
+         "IR inputs not support here!");
+
+  
+  // Use the source and file managers that we were given.
+  Clang->setFileManager(&FileMgr);
+  Clang->setSourceManager(&SourceMgr);
+
+  // Remap files.
+  PreprocessorOpts.clearRemappedFiles();
+  PreprocessorOpts.RetainRemappedFileBuffers = true;
+  for (unsigned I = 0; I != NumRemappedFiles; ++I) {
+    FilenameOrMemBuf fileOrBuf = RemappedFiles[I].second;
+    if (const llvm::MemoryBuffer *
+            memBuf = fileOrBuf.dyn_cast<const llvm::MemoryBuffer *>()) {
+      PreprocessorOpts.addRemappedFile(RemappedFiles[I].first, memBuf);
+      OwnedBuffers.push_back(memBuf);
+    } else {
+      const char *fname = fileOrBuf.get<const char *>();
+      PreprocessorOpts.addRemappedFile(RemappedFiles[I].first, fname);
+    }
+  }
+  
+  // Use the code completion consumer we were given, but adding any cached
+  // code-completion results.
+  AugmentedCodeCompleteConsumer *AugmentedConsumer
+    = new AugmentedCodeCompleteConsumer(*this, Consumer, 
+                                        FrontendOpts.ShowMacrosInCodeCompletion,
+                                FrontendOpts.ShowCodePatternsInCodeCompletion,
+                                FrontendOpts.ShowGlobalSymbolsInCodeCompletion);
+  Clang->setCodeCompletionConsumer(AugmentedConsumer);
+
+  Clang->getFrontendOpts().SkipFunctionBodies = true;
+
+  // If we have a precompiled preamble, try to use it. We only allow
+  // the use of the precompiled preamble if we're if the completion
+  // point is within the main file, after the end of the precompiled
+  // preamble.
+  llvm::MemoryBuffer *OverrideMainBuffer = 0;
+  if (!getPreambleFile(this).empty()) {
+    using llvm::sys::FileStatus;
+    llvm::sys::PathWithStatus CompleteFilePath(File);
+    llvm::sys::PathWithStatus MainPath(OriginalSourceFile);
+    if (const FileStatus *CompleteFileStatus = CompleteFilePath.getFileStatus())
+      if (const FileStatus *MainStatus = MainPath.getFileStatus())
+        if (CompleteFileStatus->getUniqueID() == MainStatus->getUniqueID() &&
+            Line > 1)
+          OverrideMainBuffer
+            = getMainBufferWithPrecompiledPreamble(*CCInvocation, false, 
+                                                   Line - 1);
+  }
+
+  // If the main file has been overridden due to the use of a preamble,
+  // make that override happen and introduce the preamble.
+  PreprocessorOpts.DisableStatCache = true;
+  StoredDiagnostics.insert(StoredDiagnostics.end(),
+                           stored_diag_begin(),
+                           stored_diag_afterDriver_begin());
+  if (OverrideMainBuffer) {
+    PreprocessorOpts.addRemappedFile(OriginalSourceFile, OverrideMainBuffer);
+    PreprocessorOpts.PrecompiledPreambleBytes.first = Preamble.size();
+    PreprocessorOpts.PrecompiledPreambleBytes.second
+                                                    = PreambleEndsAtStartOfLine;
+    PreprocessorOpts.ImplicitPCHInclude = getPreambleFile(this);
+    PreprocessorOpts.DisablePCHValidation = true;
+    
+    OwnedBuffers.push_back(OverrideMainBuffer);
+  } else {
+    PreprocessorOpts.PrecompiledPreambleBytes.first = 0;
+    PreprocessorOpts.PrecompiledPreambleBytes.second = false;
+  }
+
+  // Disable the preprocessing record
+  PreprocessorOpts.DetailedRecord = false;
+  
+  OwningPtr<SyntaxOnlyAction> Act;
+  Act.reset(new SyntaxOnlyAction);
+  if (Act->BeginSourceFile(*Clang.get(), Clang->getFrontendOpts().Inputs[0])) {
+    if (OverrideMainBuffer) {
+      std::string ModName = getPreambleFile(this);
+      TranslateStoredDiagnostics(Clang->getModuleManager(), ModName,
+                                 getSourceManager(), PreambleDiagnostics,
+                                 StoredDiagnostics);
+    }
+    Act->Execute();
+    Act->EndSourceFile();
+  }
+
+  checkAndSanitizeDiags(StoredDiagnostics, getSourceManager());
+}
+
+CXSaveError ASTUnit::Save(StringRef File) {
+  // Write to a temporary file and later rename it to the actual file, to avoid
+  // possible race conditions.
+  SmallString<128> TempPath;
+  TempPath = File;
+  TempPath += "-%%%%%%%%";
+  int fd;
+  if (llvm::sys::fs::unique_file(TempPath.str(), fd, TempPath,
+                                 /*makeAbsolute=*/false))
+    return CXSaveError_Unknown;
+
+  // FIXME: Can we somehow regenerate the stat cache here, or do we need to 
+  // unconditionally create a stat cache when we parse the file?
+  llvm::raw_fd_ostream Out(fd, /*shouldClose=*/true);
+
+  serialize(Out);
+  Out.close();
+  if (Out.has_error()) {
+    Out.clear_error();
+    return CXSaveError_Unknown;
+  }
+
+  if (llvm::sys::fs::rename(TempPath.str(), File)) {
+    bool exists;
+    llvm::sys::fs::remove(TempPath.str(), exists);
+    return CXSaveError_Unknown;
+  }
+
+  return CXSaveError_None;
+}
+
+bool ASTUnit::serialize(raw_ostream &OS) {
+  bool hasErrors = getDiagnostics().hasErrorOccurred();
+
+  SmallString<128> Buffer;
+  llvm::BitstreamWriter Stream(Buffer);
+  ASTWriter Writer(Stream);
+  // FIXME: Handle modules
+  Writer.WriteAST(getSema(), 0, std::string(), 0, "", hasErrors);
+  
+  // Write the generated bitstream to "Out".
+  if (!Buffer.empty())
+    OS.write((char *)&Buffer.front(), Buffer.size());
+
+  return false;
+}
+
+typedef ContinuousRangeMap<unsigned, int, 2> SLocRemap;
+
+static void TranslateSLoc(SourceLocation &L, SLocRemap &Remap) {
+  unsigned Raw = L.getRawEncoding();
+  const unsigned MacroBit = 1U << 31;
+  L = SourceLocation::getFromRawEncoding((Raw & MacroBit) |
+      ((Raw & ~MacroBit) + Remap.find(Raw & ~MacroBit)->second));
+}
+
+void ASTUnit::TranslateStoredDiagnostics(
+                          ASTReader *MMan,
+                          StringRef ModName,
+                          SourceManager &SrcMgr,
+                          const SmallVectorImpl<StoredDiagnostic> &Diags,
+                          SmallVectorImpl<StoredDiagnostic> &Out) {
+  // The stored diagnostic has the old source manager in it; update
+  // the locations to refer into the new source manager. We also need to remap
+  // all the locations to the new view. This includes the diag location, any
+  // associated source ranges, and the source ranges of associated fix-its.
+  // FIXME: There should be a cleaner way to do this.
+
+  SmallVector<StoredDiagnostic, 4> Result;
+  Result.reserve(Diags.size());
+  assert(MMan && "Don't have a module manager");
+  serialization::ModuleFile *Mod = MMan->ModuleMgr.lookup(ModName);
+  assert(Mod && "Don't have preamble module");
+  SLocRemap &Remap = Mod->SLocRemap;
+  for (unsigned I = 0, N = Diags.size(); I != N; ++I) {
+    // Rebuild the StoredDiagnostic.
+    const StoredDiagnostic &SD = Diags[I];
+    SourceLocation L = SD.getLocation();
+    TranslateSLoc(L, Remap);
+    FullSourceLoc Loc(L, SrcMgr);
+
+    SmallVector<CharSourceRange, 4> Ranges;
+    Ranges.reserve(SD.range_size());
+    for (StoredDiagnostic::range_iterator I = SD.range_begin(),
+                                          E = SD.range_end();
+         I != E; ++I) {
+      SourceLocation BL = I->getBegin();
+      TranslateSLoc(BL, Remap);
+      SourceLocation EL = I->getEnd();
+      TranslateSLoc(EL, Remap);
+      Ranges.push_back(CharSourceRange(SourceRange(BL, EL), I->isTokenRange()));
+    }
+
+    SmallVector<FixItHint, 2> FixIts;
+    FixIts.reserve(SD.fixit_size());
+    for (StoredDiagnostic::fixit_iterator I = SD.fixit_begin(),
+                                          E = SD.fixit_end();
+         I != E; ++I) {
+      FixIts.push_back(FixItHint());
+      FixItHint &FH = FixIts.back();
+      FH.CodeToInsert = I->CodeToInsert;
+      SourceLocation BL = I->RemoveRange.getBegin();
+      TranslateSLoc(BL, Remap);
+      SourceLocation EL = I->RemoveRange.getEnd();
+      TranslateSLoc(EL, Remap);
+      FH.RemoveRange = CharSourceRange(SourceRange(BL, EL),
+                                       I->RemoveRange.isTokenRange());
+    }
+
+    Result.push_back(StoredDiagnostic(SD.getLevel(), SD.getID(), 
+                                      SD.getMessage(), Loc, Ranges, FixIts));
+  }
+  Result.swap(Out);
+}
+
+static inline bool compLocDecl(std::pair<unsigned, Decl *> L,
+                               std::pair<unsigned, Decl *> R) {
+  return L.first < R.first;
+}
+
+void ASTUnit::addFileLevelDecl(Decl *D) {
+  assert(D);
+  
+  // We only care about local declarations.
+  if (D->isFromASTFile())
+    return;
+
+  SourceManager &SM = *SourceMgr;
+  SourceLocation Loc = D->getLocation();
+  if (Loc.isInvalid() || !SM.isLocalSourceLocation(Loc))
+    return;
+
+  // We only keep track of the file-level declarations of each file.
+  if (!D->getLexicalDeclContext()->isFileContext())
+    return;
+
+  SourceLocation FileLoc = SM.getFileLoc(Loc);
+  assert(SM.isLocalSourceLocation(FileLoc));
+  FileID FID;
+  unsigned Offset;
+  llvm::tie(FID, Offset) = SM.getDecomposedLoc(FileLoc);
+  if (FID.isInvalid())
+    return;
+
+  LocDeclsTy *&Decls = FileDecls[FID];
+  if (!Decls)
+    Decls = new LocDeclsTy();
+
+  std::pair<unsigned, Decl *> LocDecl(Offset, D);
+
+  if (Decls->empty() || Decls->back().first <= Offset) {
+    Decls->push_back(LocDecl);
+    return;
+  }
+
+  LocDeclsTy::iterator
+    I = std::upper_bound(Decls->begin(), Decls->end(), LocDecl, compLocDecl);
+
+  Decls->insert(I, LocDecl);
+}
+
+void ASTUnit::findFileRegionDecls(FileID File, unsigned Offset, unsigned Length,
+                                  SmallVectorImpl<Decl *> &Decls) {
+  if (File.isInvalid())
+    return;
+
+  if (SourceMgr->isLoadedFileID(File)) {
+    assert(Ctx->getExternalSource() && "No external source!");
+    return Ctx->getExternalSource()->FindFileRegionDecls(File, Offset, Length,
+                                                         Decls);
+  }
+
+  FileDeclsTy::iterator I = FileDecls.find(File);
+  if (I == FileDecls.end())
+    return;
+
+  LocDeclsTy &LocDecls = *I->second;
+  if (LocDecls.empty())
+    return;
+
+  LocDeclsTy::iterator
+    BeginIt = std::lower_bound(LocDecls.begin(), LocDecls.end(),
+                               std::make_pair(Offset, (Decl*)0), compLocDecl);
+  if (BeginIt != LocDecls.begin())
+    --BeginIt;
+
+  // If we are pointing at a top-level decl inside an objc container, we need
+  // to backtrack until we find it otherwise we will fail to report that the
+  // region overlaps with an objc container.
+  while (BeginIt != LocDecls.begin() &&
+         BeginIt->second->isTopLevelDeclInObjCContainer())
+    --BeginIt;
+
+  LocDeclsTy::iterator
+    EndIt = std::upper_bound(LocDecls.begin(), LocDecls.end(),
+                             std::make_pair(Offset+Length, (Decl*)0),
+                             compLocDecl);
+  if (EndIt != LocDecls.end())
+    ++EndIt;
+  
+  for (LocDeclsTy::iterator DIt = BeginIt; DIt != EndIt; ++DIt)
+    Decls.push_back(DIt->second);
+}
+
+SourceLocation ASTUnit::getLocation(const FileEntry *File,
+                                    unsigned Line, unsigned Col) const {
+  const SourceManager &SM = getSourceManager();
+  SourceLocation Loc = SM.translateFileLineCol(File, Line, Col);
+  return SM.getMacroArgExpandedLocation(Loc);
+}
+
+SourceLocation ASTUnit::getLocation(const FileEntry *File,
+                                    unsigned Offset) const {
+  const SourceManager &SM = getSourceManager();
+  SourceLocation FileLoc = SM.translateFileLineCol(File, 1, 1);
+  return SM.getMacroArgExpandedLocation(FileLoc.getLocWithOffset(Offset));
+}
+
+/// \brief If \arg Loc is a loaded location from the preamble, returns
+/// the corresponding local location of the main file, otherwise it returns
+/// \arg Loc.
+SourceLocation ASTUnit::mapLocationFromPreamble(SourceLocation Loc) {
+  FileID PreambleID;
+  if (SourceMgr)
+    PreambleID = SourceMgr->getPreambleFileID();
+
+  if (Loc.isInvalid() || Preamble.empty() || PreambleID.isInvalid())
+    return Loc;
+
+  unsigned Offs;
+  if (SourceMgr->isInFileID(Loc, PreambleID, &Offs) && Offs < Preamble.size()) {
+    SourceLocation FileLoc
+        = SourceMgr->getLocForStartOfFile(SourceMgr->getMainFileID());
+    return FileLoc.getLocWithOffset(Offs);
+  }
+
+  return Loc;
+}
+
+/// \brief If \arg Loc is a local location of the main file but inside the
+/// preamble chunk, returns the corresponding loaded location from the
+/// preamble, otherwise it returns \arg Loc.
+SourceLocation ASTUnit::mapLocationToPreamble(SourceLocation Loc) {
+  FileID PreambleID;
+  if (SourceMgr)
+    PreambleID = SourceMgr->getPreambleFileID();
+
+  if (Loc.isInvalid() || Preamble.empty() || PreambleID.isInvalid())
+    return Loc;
+
+  unsigned Offs;
+  if (SourceMgr->isInFileID(Loc, SourceMgr->getMainFileID(), &Offs) &&
+      Offs < Preamble.size()) {
+    SourceLocation FileLoc = SourceMgr->getLocForStartOfFile(PreambleID);
+    return FileLoc.getLocWithOffset(Offs);
+  }
+
+  return Loc;
+}
+
+bool ASTUnit::isInPreambleFileID(SourceLocation Loc) {
+  FileID FID;
+  if (SourceMgr)
+    FID = SourceMgr->getPreambleFileID();
+  
+  if (Loc.isInvalid() || FID.isInvalid())
+    return false;
+  
+  return SourceMgr->isInFileID(Loc, FID);
+}
+
+bool ASTUnit::isInMainFileID(SourceLocation Loc) {
+  FileID FID;
+  if (SourceMgr)
+    FID = SourceMgr->getMainFileID();
+  
+  if (Loc.isInvalid() || FID.isInvalid())
+    return false;
+  
+  return SourceMgr->isInFileID(Loc, FID);
+}
+
+SourceLocation ASTUnit::getEndOfPreambleFileID() {
+  FileID FID;
+  if (SourceMgr)
+    FID = SourceMgr->getPreambleFileID();
+  
+  if (FID.isInvalid())
+    return SourceLocation();
+
+  return SourceMgr->getLocForEndOfFile(FID);
+}
+
+SourceLocation ASTUnit::getStartOfMainFileID() {
+  FileID FID;
+  if (SourceMgr)
+    FID = SourceMgr->getMainFileID();
+  
+  if (FID.isInvalid())
+    return SourceLocation();
+  
+  return SourceMgr->getLocForStartOfFile(FID);
+}
+
+void ASTUnit::PreambleData::countLines() const {
+  NumLines = 0;
+  if (empty())
+    return;
+
+  for (std::vector<char>::const_iterator
+         I = Buffer.begin(), E = Buffer.end(); I != E; ++I) {
+    if (*I == '\n')
+      ++NumLines;
+  }
+  if (Buffer.back() != '\n')
+    ++NumLines;
+}
+
+#ifndef NDEBUG
+ASTUnit::ConcurrencyState::ConcurrencyState() {
+  Mutex = new llvm::sys::MutexImpl(/*recursive=*/true);
+}
+
+ASTUnit::ConcurrencyState::~ConcurrencyState() {
+  delete static_cast<llvm::sys::MutexImpl *>(Mutex);
+}
+
+void ASTUnit::ConcurrencyState::start() {
+  bool acquired = static_cast<llvm::sys::MutexImpl *>(Mutex)->tryacquire();
+  assert(acquired && "Concurrent access to ASTUnit!");
+}
+
+void ASTUnit::ConcurrencyState::finish() {
+  static_cast<llvm::sys::MutexImpl *>(Mutex)->release();
+}
+
+#else // NDEBUG
+
+ASTUnit::ConcurrencyState::ConcurrencyState() {}
+ASTUnit::ConcurrencyState::~ConcurrencyState() {}
+void ASTUnit::ConcurrencyState::start() {}
+void ASTUnit::ConcurrencyState::finish() {}
+
+#endif