diff --git a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp
--- a/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp
+++ b/clang-tools-extra/clang-include-fixer/find-all-symbols/FindAllMacros.cpp
@@ -10,6 +10,7 @@
 #include "HeaderMapCollector.h"
 #include "PathConfig.h"
 #include "SymbolInfo.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/MacroInfo.h"
diff --git a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h
--- a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h
+++ b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.h
@@ -13,6 +13,13 @@
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/DenseSet.h"
 
+namespace llvm {
+namespace vfs {
+class OverlayFileSystem;
+class InMemoryFileSystem;
+}
+}
+
 namespace clang {
 class CompilerInstance;
 
diff --git a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
--- a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
+++ b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "ExpandModularHeadersPPCallbacks.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Serialization/ASTReader.h"
diff --git a/clang-tools-extra/clangd/Format.cpp b/clang-tools-extra/clangd/Format.cpp
--- a/clang-tools-extra/clangd/Format.cpp
+++ b/clang-tools-extra/clangd/Format.cpp
@@ -8,6 +8,7 @@
 #include "Format.h"
 #include "Logger.h"
 #include "clang/Basic/SourceManager.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Format/Format.h"
 #include "clang/Lex/Lexer.h"
 #include "clang/Tooling/Core/Replacement.h"
diff --git a/clang-tools-extra/pp-trace/PPCallbacksTracker.cpp b/clang-tools-extra/pp-trace/PPCallbacksTracker.cpp
--- a/clang-tools-extra/pp-trace/PPCallbacksTracker.cpp
+++ b/clang-tools-extra/pp-trace/PPCallbacksTracker.cpp
@@ -14,6 +14,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "PPCallbacksTracker.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Lex/MacroArgs.h"
 #include "llvm/Support/raw_ostream.h"
 
diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -52,7 +52,6 @@
 #include "clang/AST/DeclFriend.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclTemplate.h"
-#include "clang/AST/ParentMapContext.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/ExprObjC.h"
@@ -60,6 +59,7 @@
 #include "clang/AST/NestedNameSpecifier.h"
 #include "clang/AST/OpenMPClause.h"
 #include "clang/AST/OperationKinds.h"
+#include "clang/AST/ParentMapContext.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/StmtCXX.h"
 #include "clang/AST/StmtObjC.h"
@@ -72,6 +72,7 @@
 #include "clang/ASTMatchers/ASTMatchersMacros.h"
 #include "clang/Basic/AttrKinds.h"
 #include "clang/Basic/ExceptionSpecificationType.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceManager.h"
diff --git a/clang/include/clang/Basic/SourceManager.h b/clang/include/clang/Basic/SourceManager.h
--- a/clang/include/clang/Basic/SourceManager.h
+++ b/clang/include/clang/Basic/SourceManager.h
@@ -35,7 +35,6 @@
 #define LLVM_CLANG_BASIC_SOURCEMANAGER_H
 
 #include "clang/Basic/Diagnostic.h"
-#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/BitVector.h"
@@ -60,6 +59,9 @@
 
 class ASTReader;
 class ASTWriter;
+class FileManager;
+class FileEntry;
+class FileEntryRef;
 class LineTableInfo;
 class SourceManager;
 
@@ -830,24 +832,11 @@
   /// This translates NULL into standard input.
   FileID createFileID(const FileEntry *SourceFile, SourceLocation IncludePos,
                       SrcMgr::CharacteristicKind FileCharacter,
-                      int LoadedID = 0, unsigned LoadedOffset = 0) {
-    assert(SourceFile && "Null source file!");
-    const SrcMgr::ContentCache *IR =
-        getOrCreateContentCache(SourceFile, isSystem(FileCharacter));
-    assert(IR && "getOrCreateContentCache() cannot return NULL");
-    return createFileID(IR, SourceFile->getName(), IncludePos, FileCharacter,
-                        LoadedID, LoadedOffset);
-  }
+                      int LoadedID = 0, unsigned LoadedOffset = 0);
 
   FileID createFileID(FileEntryRef SourceFile, SourceLocation IncludePos,
                       SrcMgr::CharacteristicKind FileCharacter,
-                      int LoadedID = 0, unsigned LoadedOffset = 0) {
-    const SrcMgr::ContentCache *IR = getOrCreateContentCache(
-        &SourceFile.getFileEntry(), isSystem(FileCharacter));
-    assert(IR && "getOrCreateContentCache() cannot return NULL");
-    return createFileID(IR, SourceFile.getName(), IncludePos, FileCharacter,
-                        LoadedID, LoadedOffset);
-  }
+                      int LoadedID = 0, unsigned LoadedOffset = 0);
 
   /// Create a new FileID that represents the specified memory buffer.
   ///
@@ -856,12 +845,7 @@
   FileID createFileID(std::unique_ptr<llvm::MemoryBuffer> Buffer,
                       SrcMgr::CharacteristicKind FileCharacter = SrcMgr::C_User,
                       int LoadedID = 0, unsigned LoadedOffset = 0,
-                      SourceLocation IncludeLoc = SourceLocation()) {
-    StringRef Name = Buffer->getBufferIdentifier();
-    return createFileID(
-        createMemBufferContentCache(Buffer.release(), /*DoNotFree*/ false),
-        Name, IncludeLoc, FileCharacter, LoadedID, LoadedOffset);
-  }
+                      SourceLocation IncludeLoc = SourceLocation());
 
   enum UnownedTag { Unowned };
 
@@ -872,20 +856,12 @@
   FileID createFileID(UnownedTag, const llvm::MemoryBuffer *Buffer,
                       SrcMgr::CharacteristicKind FileCharacter = SrcMgr::C_User,
                       int LoadedID = 0, unsigned LoadedOffset = 0,
-                      SourceLocation IncludeLoc = SourceLocation()) {
-    return createFileID(createMemBufferContentCache(Buffer, /*DoNotFree*/ true),
-                        Buffer->getBufferIdentifier(), IncludeLoc,
-                        FileCharacter, LoadedID, LoadedOffset);
-  }
+                      SourceLocation IncludeLoc = SourceLocation());
 
   /// Get the FileID for \p SourceFile if it exists. Otherwise, create a
   /// new FileID for the \p SourceFile.
   FileID getOrCreateFileID(const FileEntry *SourceFile,
-                           SrcMgr::CharacteristicKind FileCharacter) {
-    FileID ID = translateFile(SourceFile);
-    return ID.isValid() ? ID : createFileID(SourceFile, SourceLocation(),
-                                            FileCharacter);
-  }
+                           SrcMgr::CharacteristicKind FileCharacter);
 
   /// Return a new SourceLocation that encodes the
   /// fact that a token from SpellingLoc should actually be referenced from
@@ -1025,17 +1001,7 @@
   }
 
   /// Returns the FileEntryRef for the provided FileID.
-  Optional<FileEntryRef> getFileEntryRefForID(FileID FID) const {
-    bool Invalid = false;
-    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
-    if (Invalid || !Entry.isFile())
-      return None;
-
-    const SrcMgr::ContentCache *Content = Entry.getFile().getContentCache();
-    if (!Content || !Content->OrigEntry)
-      return None;
-    return FileEntryRef(Entry.getFile().getName(), *Content->OrigEntry);
-  }
+  Optional<FileEntryRef> getFileEntryRefForID(FileID FID) const;
 
   /// Returns the FileEntry record for the provided SLocEntry.
   const FileEntry *getFileEntryForSLocEntry(const SrcMgr::SLocEntry &sloc) const
@@ -1098,11 +1064,7 @@
   }
 
   /// Return the filename of the file containing a SourceLocation.
-  StringRef getFilename(SourceLocation SpellingLoc) const {
-    if (const FileEntry *F = getFileEntryForID(getFileID(SpellingLoc)))
-      return F->getName();
-    return StringRef();
-  }
+  StringRef getFilename(SourceLocation SpellingLoc) const;
 
   /// Return the source location corresponding to the first byte of
   /// the specified file.
diff --git a/clang/include/clang/Frontend/CompilerInstance.h b/clang/include/clang/Frontend/CompilerInstance.h
--- a/clang/include/clang/Frontend/CompilerInstance.h
+++ b/clang/include/clang/Frontend/CompilerInstance.h
@@ -390,9 +390,7 @@
   /// @name Virtual File System
   /// {
 
-  llvm::vfs::FileSystem &getVirtualFileSystem() const {
-    return getFileManager().getVirtualFileSystem();
-  }
+  llvm::vfs::FileSystem &getVirtualFileSystem() const;
 
   /// }
   /// @name File Manager
diff --git a/clang/include/clang/Frontend/VerifyDiagnosticConsumer.h b/clang/include/clang/Frontend/VerifyDiagnosticConsumer.h
--- a/clang/include/clang/Frontend/VerifyDiagnosticConsumer.h
+++ b/clang/include/clang/Frontend/VerifyDiagnosticConsumer.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_FRONTEND_VERIFYDIAGNOSTICCONSUMER_H
 
 #include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Lex/Preprocessor.h"
diff --git a/clang/include/clang/Lex/DirectoryLookup.h b/clang/include/clang/Lex/DirectoryLookup.h
--- a/clang/include/clang/Lex/DirectoryLookup.h
+++ b/clang/include/clang/Lex/DirectoryLookup.h
@@ -14,13 +14,12 @@
 #define LLVM_CLANG_LEX_DIRECTORYLOOKUP_H
 
 #include "clang/Basic/LLVM.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/ModuleMap.h"
 
 namespace clang {
 class HeaderMap;
-class DirectoryEntry;
-class FileEntry;
 class HeaderSearch;
 class Module;
 
diff --git a/clang/include/clang/Lex/ModuleMap.h b/clang/include/clang/Lex/ModuleMap.h
--- a/clang/include/clang/Lex/ModuleMap.h
+++ b/clang/include/clang/Lex/ModuleMap.h
@@ -605,9 +605,7 @@
     return &I->second;
   }
 
-  void addAdditionalModuleMapFile(const Module *M, const FileEntry *ModuleMap) {
-    AdditionalModMaps[M].insert(ModuleMap);
-  }
+  void addAdditionalModuleMapFile(const Module *M, const FileEntry *ModuleMap);
 
   /// Resolve all of the unresolved exports in the given module.
   ///
diff --git a/clang/include/clang/Lex/PPCallbacks.h b/clang/include/clang/Lex/PPCallbacks.h
--- a/clang/include/clang/Lex/PPCallbacks.h
+++ b/clang/include/clang/Lex/PPCallbacks.h
@@ -308,7 +308,7 @@
   /// read.
   virtual void HasInclude(SourceLocation Loc, StringRef FileName, bool IsAngled,
                           Optional<FileEntryRef> File,
-                          SrcMgr::CharacteristicKind FileType) {}
+                          SrcMgr::CharacteristicKind FileType);
 
   /// Hook called when a source range is skipped.
   /// \param Range The SourceRange that was skipped. The range begins at the
@@ -374,7 +374,6 @@
 
 /// Simple wrapper class for chaining callbacks.
 class PPChainedCallbacks : public PPCallbacks {
-  virtual void anchor();
   std::unique_ptr<PPCallbacks> First, Second;
 
 public:
@@ -382,6 +381,8 @@
                      std::unique_ptr<PPCallbacks> _Second)
     : First(std::move(_First)), Second(std::move(_Second)) {}
 
+  ~PPChainedCallbacks() override;
+
   void FileChanged(SourceLocation Loc, FileChangeReason Reason,
                    SrcMgr::CharacteristicKind FileType,
                    FileID PrevFID) override {
@@ -490,10 +491,7 @@
 
   void HasInclude(SourceLocation Loc, StringRef FileName, bool IsAngled,
                   Optional<FileEntryRef> File,
-                  SrcMgr::CharacteristicKind FileType) override {
-    First->HasInclude(Loc, FileName, IsAngled, File, FileType);
-    Second->HasInclude(Loc, FileName, IsAngled, File, FileType);
-  }
+                  SrcMgr::CharacteristicKind FileType) override;
 
   void PragmaOpenCLExtension(SourceLocation NameLoc, const IdentifierInfo *Name,
                              SourceLocation StateLoc, unsigned State) override {
diff --git a/clang/lib/AST/ExternalASTSource.cpp b/clang/lib/AST/ExternalASTSource.cpp
--- a/clang/lib/AST/ExternalASTSource.cpp
+++ b/clang/lib/AST/ExternalASTSource.cpp
@@ -15,6 +15,7 @@
 #include "clang/AST/ExternalASTSource.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclarationName.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/Module.h"
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -25,6 +25,7 @@
 #include "clang/AST/VTableBuilder.h"
 #include "clang/Basic/ABI.h"
 #include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/StringExtras.h"
diff --git a/clang/lib/Basic/SanitizerBlacklist.cpp b/clang/lib/Basic/SanitizerBlacklist.cpp
--- a/clang/lib/Basic/SanitizerBlacklist.cpp
+++ b/clang/lib/Basic/SanitizerBlacklist.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Basic/SanitizerBlacklist.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SanitizerSpecialCaseList.h"
 #include "clang/Basic/Sanitizers.h"
 #include "clang/Basic/SourceManager.h"
diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -17,12 +17,12 @@
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/SourceManagerInternals.h"
 #include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/None.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Capacity.h"
 #include "llvm/Support/Compiler.h"
@@ -560,6 +560,70 @@
 // Methods to create new FileID's and macro expansions.
 //===----------------------------------------------------------------------===//
 
+/// Create a new FileID that represents the specified file
+/// being \#included from the specified IncludePosition.
+///
+/// This translates NULL into standard input.
+FileID SourceManager::createFileID(const FileEntry *SourceFile,
+                                   SourceLocation IncludePos,
+                                   SrcMgr::CharacteristicKind FileCharacter,
+                                   int LoadedID, unsigned LoadedOffset) {
+  assert(SourceFile && "Null source file!");
+  const SrcMgr::ContentCache *IR =
+      getOrCreateContentCache(SourceFile, isSystem(FileCharacter));
+  assert(IR && "getOrCreateContentCache() cannot return NULL");
+  return createFileID(IR, SourceFile->getName(), IncludePos, FileCharacter,
+		      LoadedID, LoadedOffset);
+}
+
+FileID SourceManager::createFileID(FileEntryRef SourceFile,
+                                   SourceLocation IncludePos,
+                                   SrcMgr::CharacteristicKind FileCharacter,
+                                   int LoadedID, unsigned LoadedOffset) {
+  const SrcMgr::ContentCache *IR = getOrCreateContentCache(
+      &SourceFile.getFileEntry(), isSystem(FileCharacter));
+  assert(IR && "getOrCreateContentCache() cannot return NULL");
+  return createFileID(IR, SourceFile.getName(), IncludePos, FileCharacter,
+		      LoadedID, LoadedOffset);
+}
+
+/// Create a new FileID that represents the specified memory buffer.
+///
+/// This does no caching of the buffer and takes ownership of the
+/// MemoryBuffer, so only pass a MemoryBuffer to this once.
+FileID SourceManager::createFileID(std::unique_ptr<llvm::MemoryBuffer> Buffer,
+                                   SrcMgr::CharacteristicKind FileCharacter,
+                                   int LoadedID, unsigned LoadedOffset,
+                                   SourceLocation IncludeLoc) {
+  StringRef Name = Buffer->getBufferIdentifier();
+  return createFileID(
+      createMemBufferContentCache(Buffer.release(), /*DoNotFree*/ false),
+      Name, IncludeLoc, FileCharacter, LoadedID, LoadedOffset);
+}
+
+/// Create a new FileID that represents the specified memory buffer.
+///
+/// This does not take ownership of the MemoryBuffer. The memory buffer must
+/// outlive the SourceManager.
+FileID SourceManager::createFileID(UnownedTag, const llvm::MemoryBuffer *Buffer,
+                                   SrcMgr::CharacteristicKind FileCharacter,
+                                   int LoadedID, unsigned LoadedOffset,
+                                   SourceLocation IncludeLoc) {
+  return createFileID(createMemBufferContentCache(Buffer, /*DoNotFree*/ true),
+		      Buffer->getBufferIdentifier(), IncludeLoc,
+		      FileCharacter, LoadedID, LoadedOffset);
+}
+
+/// Get the FileID for \p SourceFile if it exists. Otherwise, create a
+/// new FileID for the \p SourceFile.
+FileID
+SourceManager::getOrCreateFileID(const FileEntry *SourceFile,
+                                 SrcMgr::CharacteristicKind FileCharacter) {
+  FileID ID = translateFile(SourceFile);
+  return ID.isValid() ? ID : createFileID(SourceFile, SourceLocation(),
+					  FileCharacter);
+}
+
 /// createFileID - Create a new FileID for the specified ContentCache and
 /// include position.  This works regardless of whether the ContentCache
 /// corresponds to a file or some other input source.
@@ -701,6 +765,18 @@
   const_cast<SrcMgr::ContentCache *>(CC)->IsTransient = true;
 }
 
+Optional<FileEntryRef> SourceManager::getFileEntryRefForID(FileID FID) const {
+  bool Invalid = false;
+  const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+  if (Invalid || !Entry.isFile())
+    return None;
+
+  const SrcMgr::ContentCache *Content = Entry.getFile().getContentCache();
+  if (!Content || !Content->OrigEntry)
+    return None;
+  return FileEntryRef(Entry.getFile().getName(), *Content->OrigEntry);
+}
+
 StringRef SourceManager::getBufferData(FileID FID, bool *Invalid) const {
   bool MyInvalid = false;
   const SLocEntry &SLoc = getSLocEntry(FID, &MyInvalid);
@@ -992,6 +1068,13 @@
   return Loc.getLocWithOffset(LocInfo.second);
 }
 
+/// Return the filename of the file containing a SourceLocation.
+StringRef SourceManager::getFilename(SourceLocation SpellingLoc) const {
+  if (const FileEntry *F = getFileEntryForID(getFileID(SpellingLoc)))
+    return F->getName();
+  return StringRef();
+}
+
 /// getImmediateExpansionRange - Loc is required to be an expansion location.
 /// Return the start/end of the expansion information.
 CharSourceRange
diff --git a/clang/lib/Basic/XRayLists.cpp b/clang/lib/Basic/XRayLists.cpp
--- a/clang/lib/Basic/XRayLists.cpp
+++ b/clang/lib/Basic/XRayLists.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Basic/XRayLists.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "llvm/Support/SpecialCaseList.h"
 
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -21,6 +21,7 @@
 #include "clang/AST/StmtOpenMP.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Basic/BitmaskEnum.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/OpenMPKinds.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/CodeGen/ConstantInitBuilder.h"
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -38,6 +38,7 @@
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/CodeGenOptions.h"
 #include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/Module.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -14,11 +14,12 @@
 #include "CodeGenFunction.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
 #include "clang/Lex/Lexer.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringExtras.h"
-#include "llvm/ADT/Optional.h"
 #include "llvm/ProfileData/Coverage/CoverageMapping.h"
 #include "llvm/ProfileData/Coverage/CoverageMappingReader.h"
 #include "llvm/ProfileData/Coverage/CoverageMappingWriter.h"
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -97,6 +97,10 @@
 void CompilerInstance::setTarget(TargetInfo *Value) { Target = Value; }
 void CompilerInstance::setAuxTarget(TargetInfo *Value) { AuxTarget = Value; }
 
+llvm::vfs::FileSystem &CompilerInstance::getVirtualFileSystem() const {
+  return getFileManager().getVirtualFileSystem();
+}
+
 void CompilerInstance::setFileManager(FileManager *Value) {
   FileMgr = Value;
 }
diff --git a/clang/lib/Frontend/PrecompiledPreamble.cpp b/clang/lib/Frontend/PrecompiledPreamble.cpp
--- a/clang/lib/Frontend/PrecompiledPreamble.cpp
+++ b/clang/lib/Frontend/PrecompiledPreamble.cpp
@@ -12,6 +12,7 @@
 
 #include "clang/Frontend/PrecompiledPreamble.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/LangStandard.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Frontend/CompilerInstance.h"
diff --git a/clang/lib/Index/CommentToXML.cpp b/clang/lib/Index/CommentToXML.cpp
--- a/clang/lib/Index/CommentToXML.cpp
+++ b/clang/lib/Index/CommentToXML.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/Attr.h"
 #include "clang/AST/Comment.h"
 #include "clang/AST/CommentVisitor.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Format/Format.h"
 #include "clang/Index/USRGeneration.h"
diff --git a/clang/lib/Index/USRGeneration.cpp b/clang/lib/Index/USRGeneration.cpp
--- a/clang/lib/Index/USRGeneration.cpp
+++ b/clang/lib/Index/USRGeneration.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/Attr.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/DeclVisitor.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Lex/PreprocessingRecord.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -1244,6 +1244,11 @@
   InferredModuleAllowedBy[M] = ModMap;
 }
 
+void ModuleMap::addAdditionalModuleMapFile(const Module *M,
+                                           const FileEntry *ModuleMap) {
+  AdditionalModMaps[M].insert(ModuleMap);
+}
+
 LLVM_DUMP_METHOD void ModuleMap::dump() {
   llvm::errs() << "Modules:";
   for (llvm::StringMap<Module *>::iterator M = Modules.begin(),
diff --git a/clang/lib/Lex/PPCallbacks.cpp b/clang/lib/Lex/PPCallbacks.cpp
--- a/clang/lib/Lex/PPCallbacks.cpp
+++ b/clang/lib/Lex/PPCallbacks.cpp
@@ -7,7 +7,24 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Lex/PPCallbacks.h"
+#include "clang/Basic/FileManager.h"
 
 using namespace clang;
 
-void PPChainedCallbacks::anchor() { }
+// Out of line key method.
+PPCallbacks::~PPCallbacks() = default;
+
+void PPCallbacks::HasInclude(SourceLocation Loc, StringRef FileName,
+                             bool IsAngled, Optional<FileEntryRef> File,
+                             SrcMgr::CharacteristicKind FileType) {}
+
+// Out of line key method.
+PPChainedCallbacks::~PPChainedCallbacks() = default;
+
+void PPChainedCallbacks::HasInclude(SourceLocation Loc, StringRef FileName,
+                                    bool IsAngled, Optional<FileEntryRef> File,
+                                    SrcMgr::CharacteristicKind FileType) {
+  First->HasInclude(Loc, FileName, IsAngled, File, FileType);
+  Second->HasInclude(Loc, FileName, IsAngled, File, FileType);
+}
+
diff --git a/clang/lib/Lex/PPLexerChange.cpp b/clang/lib/Lex/PPLexerChange.cpp
--- a/clang/lib/Lex/PPLexerChange.cpp
+++ b/clang/lib/Lex/PPLexerChange.cpp
@@ -24,8 +24,6 @@
 #include "llvm/Support/Path.h"
 using namespace clang;
 
-PPCallbacks::~PPCallbacks() {}
-
 //===----------------------------------------------------------------------===//
 // Miscellaneous Methods.
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -14,6 +14,7 @@
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclTemplate.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Parse/ParseDiagnostic.h"
 #include "clang/Parse/RAIIObjectsForParser.h"
 #include "clang/Sema/DeclSpec.h"
diff --git a/clang/lib/StaticAnalyzer/Core/SarifDiagnostics.cpp b/clang/lib/StaticAnalyzer/Core/SarifDiagnostics.cpp
--- a/clang/lib/StaticAnalyzer/Core/SarifDiagnostics.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SarifDiagnostics.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Analysis/PathDiagnostic.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/Version.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/StaticAnalyzer/Core/AnalyzerOptions.h"
diff --git a/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp b/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp
--- a/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp
+++ b/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Tooling/Inclusions/HeaderIncludes.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/Optional.h"
diff --git a/clang/tools/clang-import-test/clang-import-test.cpp b/clang/tools/clang-import-test/clang-import-test.cpp
--- a/clang/tools/clang-import-test/clang-import-test.cpp
+++ b/clang/tools/clang-import-test/clang-import-test.cpp
@@ -11,6 +11,7 @@
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/ExternalASTMerger.h"
 #include "clang/Basic/Builtins.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/TargetInfo.h"
diff --git a/clang/tools/clang-refactor/TestSupport.cpp b/clang/tools/clang-refactor/TestSupport.cpp
--- a/clang/tools/clang-refactor/TestSupport.cpp
+++ b/clang/tools/clang-refactor/TestSupport.cpp
@@ -14,6 +14,7 @@
 
 #include "TestSupport.h"
 #include "clang/Basic/DiagnosticError.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/STLExtras.h"
diff --git a/clang/tools/libclang/CXSourceLocation.cpp b/clang/tools/libclang/CXSourceLocation.cpp
--- a/clang/tools/libclang/CXSourceLocation.cpp
+++ b/clang/tools/libclang/CXSourceLocation.cpp
@@ -10,13 +10,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/Frontend/ASTUnit.h"
+#include "CXSourceLocation.h"
 #include "CIndexer.h"
 #include "CLog.h"
 #include "CXLoadedDiagnostic.h"
-#include "CXSourceLocation.h"
 #include "CXString.h"
 #include "CXTranslationUnit.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Frontend/ASTUnit.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Format.h"
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
@@ -9,6 +9,7 @@
 #include "ClangExpressionSourceCode.h"
 
 #include "clang/Basic/CharInfo.h"
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/StringRef.h"
diff --git a/lldb/source/Plugins/Language/ClangCommon/ClangHighlighter.cpp b/lldb/source/Plugins/Language/ClangCommon/ClangHighlighter.cpp
--- a/lldb/source/Plugins/Language/ClangCommon/ClangHighlighter.cpp
+++ b/lldb/source/Plugins/Language/ClangCommon/ClangHighlighter.cpp
@@ -13,6 +13,7 @@
 #include "lldb/Utility/AnsiTerminal.h"
 #include "lldb/Utility/StreamString.h"
 
+#include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/StringSet.h"