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 //===- SourceManager.h - Track and cache source files -----------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 /// \file
 /// Defines the SourceManager interface.
 ///
 /// There are three different types of locations in a %file: a spelling
 /// location, an expansion location, and a presumed location.
 ///
 /// Given an example of:
 /// \code
 /// #define min(x, y) x < y ? x : y
 /// \endcode
 ///
 /// and then later on a use of min:
 /// \code
 /// #line 17
 /// return min(a, b);
 /// \endcode
 ///
 /// The expansion location is the line in the source code where the macro
 /// was expanded (the return statement), the spelling location is the
 /// location in the source where the macro was originally defined,
 /// and the presumed location is where the line directive states that
 /// the line is 17, or any other line.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CLANG_BASIC_SOURCEMANAGER_H
 #define LLVM_CLANG_BASIC_SOURCEMANAGER_H
 
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/FileEntry.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/PagedVector.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include <cassert>
 #include <cstddef>
 #include <map>
 #include <memory>
 #include <optional>
 #include <string>
 #include <utility>
 #include <vector>
 
 namespace clang {
 
 class ASTReader;
 class ASTWriter;
 class FileManager;
 class LineTableInfo;
 class SourceManager;
 
 /// Public enums and private classes that are part of the
 /// SourceManager implementation.
 namespace SrcMgr {
 
 /// Indicates whether a file or directory holds normal user code,
 /// system code, or system code which is implicitly 'extern "C"' in C++ mode.
 ///
 /// Entire directories can be tagged with this (this is maintained by
 /// DirectoryLookup and friends) as can specific FileInfos when a \#pragma
 /// system_header is seen or in various other cases.
 ///
 enum CharacteristicKind {
   C_User,
   C_System,
   C_ExternCSystem,
   C_User_ModuleMap,
   C_System_ModuleMap
 };
 
 /// Determine whether a file / directory characteristic is for system code.
 inline bool isSystem(CharacteristicKind CK) {
   return CK != C_User && CK != C_User_ModuleMap;
 }
 
 /// Determine whether a file characteristic is for a module map.
 inline bool isModuleMap(CharacteristicKind CK) {
   return CK == C_User_ModuleMap || CK == C_System_ModuleMap;
 }
 
 /// Mapping of line offsets into a source file. This does not own the storage
 /// for the line numbers.
 class LineOffsetMapping {
 public:
   explicit operator bool() const { return Storage; }
   unsigned size() const {
     assert(Storage);
     return Storage[0];
   }
   ArrayRef<unsigned> getLines() const {
     assert(Storage);
     return ArrayRef<unsigned>(Storage + 1, Storage + 1 + size());
   }
   const unsigned *begin() const { return getLines().begin(); }
   const unsigned *end() const { return getLines().end(); }
   const unsigned &operator[](int I) const { return getLines()[I]; }
 
   static LineOffsetMapping get(llvm::MemoryBufferRef Buffer,
                                llvm::BumpPtrAllocator &Alloc);
 
   LineOffsetMapping() = default;
   LineOffsetMapping(ArrayRef<unsigned> LineOffsets,
                     llvm::BumpPtrAllocator &Alloc);
 
 private:
   /// First element is the size, followed by elements at off-by-one indexes.
   unsigned *Storage = nullptr;
 };
 
 /// One instance of this struct is kept for every file loaded or used.
 ///
 /// This object owns the MemoryBuffer object.
 class alignas(8) ContentCache {
   /// The actual buffer containing the characters from the input
   /// file.
   mutable std::unique_ptr<llvm::MemoryBuffer> Buffer;
 
 public:
   /// Reference to the file entry representing this ContentCache.
   ///
   /// This reference does not own the FileEntry object.
   ///
   /// It is possible for this to be NULL if the ContentCache encapsulates
   /// an imaginary text buffer.
   ///
   /// FIXME: Make non-optional using a virtual file as needed, remove \c
   /// Filename and use \c OrigEntry.getNameAsRequested() instead.
   OptionalFileEntryRef OrigEntry;
 
   /// References the file which the contents were actually loaded from.
   ///
   /// Can be different from 'Entry' if we overridden the contents of one file
   /// with the contents of another file.
   OptionalFileEntryRef ContentsEntry;
 
   /// The filename that is used to access OrigEntry.
   ///
   /// FIXME: Remove this once OrigEntry is a FileEntryRef with a stable name.
   StringRef Filename;
 
   /// A bump pointer allocated array of offsets for each source line.
   ///
   /// This is lazily computed.  The lines are owned by the SourceManager
   /// BumpPointerAllocator object.
   mutable LineOffsetMapping SourceLineCache;
 
   /// Indicates whether the buffer itself was provided to override
   /// the actual file contents.
   ///
   /// When true, the original entry may be a virtual file that does not
   /// exist.
   LLVM_PREFERRED_TYPE(bool)
   unsigned BufferOverridden : 1;
 
   /// True if this content cache was initially created for a source file
   /// considered to be volatile (likely to change between stat and open).
   LLVM_PREFERRED_TYPE(bool)
   unsigned IsFileVolatile : 1;
 
   /// True if this file may be transient, that is, if it might not
   /// exist at some later point in time when this content entry is used,
   /// after serialization and deserialization.
   LLVM_PREFERRED_TYPE(bool)
   unsigned IsTransient : 1;
 
   LLVM_PREFERRED_TYPE(bool)
   mutable unsigned IsBufferInvalid : 1;
 
   ContentCache()
       : OrigEntry(std::nullopt), ContentsEntry(std::nullopt),
         BufferOverridden(false), IsFileVolatile(false), IsTransient(false),
         IsBufferInvalid(false) {}
 
   ContentCache(FileEntryRef Ent) : ContentCache(Ent, Ent) {}
 
   ContentCache(FileEntryRef Ent, FileEntryRef contentEnt)
       : OrigEntry(Ent), ContentsEntry(contentEnt), BufferOverridden(false),
         IsFileVolatile(false), IsTransient(false), IsBufferInvalid(false) {}
 
   /// The copy ctor does not allow copies where source object has either
   /// a non-NULL Buffer or SourceLineCache.  Ownership of allocated memory
   /// is not transferred, so this is a logical error.
   ContentCache(const ContentCache &RHS)
       : BufferOverridden(false), IsFileVolatile(false), IsTransient(false),
         IsBufferInvalid(false) {
     OrigEntry = RHS.OrigEntry;
     ContentsEntry = RHS.ContentsEntry;
 
     assert(!RHS.Buffer && !RHS.SourceLineCache &&
            "Passed ContentCache object cannot own a buffer.");
   }
 
   ContentCache &operator=(const ContentCache &RHS) = delete;
 
   /// Returns the memory buffer for the associated content.
   ///
   /// \param Diag Object through which diagnostics will be emitted if the
   ///   buffer cannot be retrieved.
   ///
   /// \param Loc If specified, is the location that invalid file diagnostics
   ///   will be emitted at.
   std::optional<llvm::MemoryBufferRef>
   getBufferOrNone(DiagnosticsEngine &Diag, FileManager &FM,
                   SourceLocation Loc = SourceLocation()) const;
 
   /// Returns the size of the content encapsulated by this
   /// ContentCache.
   ///
   /// This can be the size of the source file or the size of an
   /// arbitrary scratch buffer.  If the ContentCache encapsulates a source
   /// file this size is retrieved from the file's FileEntry.
   unsigned getSize() const;
 
   /// Returns the number of bytes actually mapped for this
   /// ContentCache.
   ///
   /// This can be 0 if the MemBuffer was not actually expanded.
   unsigned getSizeBytesMapped() const;
 
   /// Returns the kind of memory used to back the memory buffer for
   /// this content cache.  This is used for performance analysis.
   llvm::MemoryBuffer::BufferKind getMemoryBufferKind() const;
 
   /// Return the buffer, only if it has been loaded.
   std::optional<llvm::MemoryBufferRef> getBufferIfLoaded() const {
     if (Buffer)
       return Buffer->getMemBufferRef();
     return std::nullopt;
   }
 
   /// Return a StringRef to the source buffer data, only if it has already
   /// been loaded.
   std::optional<StringRef> getBufferDataIfLoaded() const {
     if (Buffer)
       return Buffer->getBuffer();
     return std::nullopt;
   }
 
   /// Set the buffer.
   void setBuffer(std::unique_ptr<llvm::MemoryBuffer> B) {
     IsBufferInvalid = false;
     Buffer = std::move(B);
   }
 
   /// Set the buffer to one that's not owned (or to nullptr).
   ///
   /// \pre Buffer cannot already be set.
   void setUnownedBuffer(std::optional<llvm::MemoryBufferRef> B) {
     assert(!Buffer && "Expected to be called right after construction");
     if (B)
       setBuffer(llvm::MemoryBuffer::getMemBuffer(*B));
   }
 
   // If BufStr has an invalid BOM, returns the BOM name; otherwise, returns
   // nullptr
   static const char *getInvalidBOM(StringRef BufStr);
 };
 
 // Assert that the \c ContentCache objects will always be 8-byte aligned so
 // that we can pack 3 bits of integer into pointers to such objects.
 static_assert(alignof(ContentCache) >= 8,
               "ContentCache must be 8-byte aligned.");
 
 /// Information about a FileID, basically just the logical file
 /// that it represents and include stack information.
 ///
 /// Each FileInfo has include stack information, indicating where it came
 /// from. This information encodes the \#include chain that a token was
 /// expanded from. The main include file has an invalid IncludeLoc.
 ///
 /// FileInfo should not grow larger than ExpansionInfo. Doing so will
 /// cause memory to bloat in compilations with many unloaded macro
 /// expansions, since the two data structurs are stored in a union in
 /// SLocEntry. Extra fields should instead go in "ContentCache *", which
 /// stores file contents and other bits on the side.
 ///
 class FileInfo {
   friend class clang::SourceManager;
   friend class clang::ASTWriter;
   friend class clang::ASTReader;
 
   /// The location of the \#include that brought in this file.
   ///
   /// This is an invalid SLOC for the main file (top of the \#include chain).
   SourceLocation IncludeLoc;
 
   /// Number of FileIDs (files and macros) that were created during
   /// preprocessing of this \#include, including this SLocEntry.
   ///
   /// Zero means the preprocessor didn't provide such info for this SLocEntry.
   unsigned NumCreatedFIDs : 31;
 
   /// Whether this FileInfo has any \#line directives.
   LLVM_PREFERRED_TYPE(bool)
   unsigned HasLineDirectives : 1;
 
   /// The content cache and the characteristic of the file.
   llvm::PointerIntPair<const ContentCache *, 3, CharacteristicKind>
       ContentAndKind;
 
 public:
   /// Return a FileInfo object.
   static FileInfo get(SourceLocation IL, ContentCache &Con,
                       CharacteristicKind FileCharacter, StringRef Filename) {
     FileInfo X;
     X.IncludeLoc = IL;
     X.NumCreatedFIDs = 0;
     X.HasLineDirectives = false;
     X.ContentAndKind.setPointer(&Con);
     X.ContentAndKind.setInt(FileCharacter);
     Con.Filename = Filename;
     return X;
   }
 
   SourceLocation getIncludeLoc() const {
     return IncludeLoc;
   }
 
   const ContentCache &getContentCache() const {
     return *ContentAndKind.getPointer();
   }
 
   /// Return whether this is a system header or not.
   CharacteristicKind getFileCharacteristic() const {
     return ContentAndKind.getInt();
   }
 
   /// Return true if this FileID has \#line directives in it.
   bool hasLineDirectives() const { return HasLineDirectives; }
 
   /// Set the flag that indicates that this FileID has
   /// line table entries associated with it.
   void setHasLineDirectives() { HasLineDirectives = true; }
 
   /// Returns the name of the file that was used when the file was loaded from
   /// the underlying file system.
   StringRef getName() const { return getContentCache().Filename; }
 };
 
 /// Each ExpansionInfo encodes the expansion location - where
 /// the token was ultimately expanded, and the SpellingLoc - where the actual
 /// character data for the token came from.
 class ExpansionInfo {
   // Really these are all SourceLocations.
 
   /// Where the spelling for the token can be found.
   SourceLocation SpellingLoc;
 
   /// In a macro expansion, ExpansionLocStart and ExpansionLocEnd
   /// indicate the start and end of the expansion. In object-like macros,
   /// they will be the same. In a function-like macro expansion, the start
   /// will be the identifier and the end will be the ')'. Finally, in
   /// macro-argument instantiations, the end will be 'SourceLocation()', an
   /// invalid location.
   SourceLocation ExpansionLocStart, ExpansionLocEnd;
 
   /// Whether the expansion range is a token range.
   bool ExpansionIsTokenRange;
 
 public:
   SourceLocation getSpellingLoc() const {
     return SpellingLoc.isInvalid() ? getExpansionLocStart() : SpellingLoc;
   }
 
   SourceLocation getExpansionLocStart() const {
     return ExpansionLocStart;
   }
 
   SourceLocation getExpansionLocEnd() const {
     return ExpansionLocEnd.isInvalid() ? getExpansionLocStart()
                                        : ExpansionLocEnd;
   }
 
   bool isExpansionTokenRange() const { return ExpansionIsTokenRange; }
 
   CharSourceRange getExpansionLocRange() const {
     return CharSourceRange(
         SourceRange(getExpansionLocStart(), getExpansionLocEnd()),
         isExpansionTokenRange());
   }
 
   bool isMacroArgExpansion() const {
     // Note that this needs to return false for default constructed objects.
     return getExpansionLocStart().isValid() && ExpansionLocEnd.isInvalid();
   }
 
   bool isMacroBodyExpansion() const {
     return getExpansionLocStart().isValid() && ExpansionLocEnd.isValid();
   }
 
   bool isFunctionMacroExpansion() const {
     return getExpansionLocStart().isValid() &&
            getExpansionLocStart() != getExpansionLocEnd();
   }
 
   /// Return a ExpansionInfo for an expansion.
   ///
   /// Start and End specify the expansion range (where the macro is
   /// expanded), and SpellingLoc specifies the spelling location (where
   /// the characters from the token come from). All three can refer to
   /// normal File SLocs or expansion locations.
   static ExpansionInfo create(SourceLocation SpellingLoc, SourceLocation Start,
                               SourceLocation End,
                               bool ExpansionIsTokenRange = true) {
     ExpansionInfo X;
     X.SpellingLoc = SpellingLoc;
     X.ExpansionLocStart = Start;
     X.ExpansionLocEnd = End;
     X.ExpansionIsTokenRange = ExpansionIsTokenRange;
     return X;
   }
 
   /// Return a special ExpansionInfo for the expansion of
   /// a macro argument into a function-like macro's body.
   ///
   /// ExpansionLoc specifies the expansion location (where the macro is
   /// expanded). This doesn't need to be a range because a macro is always
   /// expanded at a macro parameter reference, and macro parameters are
   /// always exactly one token. SpellingLoc specifies the spelling location
   /// (where the characters from the token come from). ExpansionLoc and
   /// SpellingLoc can both refer to normal File SLocs or expansion locations.
   ///
   /// Given the code:
   /// \code
   ///   #define F(x) f(x)
   ///   F(42);
   /// \endcode
   ///
   /// When expanding '\c F(42)', the '\c x' would call this with an
   /// SpellingLoc pointing at '\c 42' and an ExpansionLoc pointing at its
   /// location in the definition of '\c F'.
   static ExpansionInfo createForMacroArg(SourceLocation SpellingLoc,
                                          SourceLocation ExpansionLoc) {
     // We store an intentionally invalid source location for the end of the
     // expansion range to mark that this is a macro argument location rather
     // than a normal one.
     return create(SpellingLoc, ExpansionLoc, SourceLocation());
   }
 
   /// Return a special ExpansionInfo representing a token that ends
   /// prematurely. This is used to model a '>>' token that has been split
   /// into '>' tokens and similar cases. Unlike for the other forms of
   /// expansion, the expansion range in this case is a character range, not
   /// a token range.
   static ExpansionInfo createForTokenSplit(SourceLocation SpellingLoc,
                                            SourceLocation Start,
                                            SourceLocation End) {
     return create(SpellingLoc, Start, End, false);
   }
 };
 
 // Assert that the \c FileInfo objects are no bigger than \c ExpansionInfo
 // objects. This controls the size of \c SLocEntry, of which we have one for
 // each macro expansion. The number of (unloaded) macro expansions can be
 // very large. Any other fields needed in FileInfo should go in ContentCache.
 static_assert(sizeof(FileInfo) <= sizeof(ExpansionInfo),
               "FileInfo must be no larger than ExpansionInfo.");
 
 /// This is a discriminated union of FileInfo and ExpansionInfo.
 ///
 /// SourceManager keeps an array of these objects, and they are uniquely
 /// identified by the FileID datatype.
 class SLocEntry {
   static constexpr int OffsetBits = 8 * sizeof(SourceLocation::UIntTy) - 1;
   SourceLocation::UIntTy Offset : OffsetBits;
   LLVM_PREFERRED_TYPE(bool)
   SourceLocation::UIntTy IsExpansion : 1;
   union {
     FileInfo File;
     ExpansionInfo Expansion;
   };
 
 public:
   SLocEntry() : Offset(), IsExpansion(), File() {}
 
   SourceLocation::UIntTy getOffset() const { return Offset; }
 
   bool isExpansion() const { return IsExpansion; }
   bool isFile() const { return !isExpansion(); }
 
   const FileInfo &getFile() const {
     return const_cast<SLocEntry *>(this)->getFile();
   }
 
   FileInfo &getFile() {
     assert(isFile() && "Not a file SLocEntry!");
     return File;
   }
 
   const ExpansionInfo &getExpansion() const {
     assert(isExpansion() && "Not a macro expansion SLocEntry!");
     return Expansion;
   }
 
   /// Creates an incomplete SLocEntry that is only able to report its offset.
   static SLocEntry getOffsetOnly(SourceLocation::UIntTy Offset) {
     assert(!(Offset & (1ULL << OffsetBits)) && "Offset is too large");
     SLocEntry E;
     E.Offset = Offset;
     return E;
   }
 
   static SLocEntry get(SourceLocation::UIntTy Offset, const FileInfo &FI) {
     assert(!(Offset & (1ULL << OffsetBits)) && "Offset is too large");
     SLocEntry E;
     E.Offset = Offset;
     E.IsExpansion = false;
     E.File = FI;
     return E;
   }
 
   static SLocEntry get(SourceLocation::UIntTy Offset,
                        const ExpansionInfo &Expansion) {
     assert(!(Offset & (1ULL << OffsetBits)) && "Offset is too large");
     SLocEntry E;
     E.Offset = Offset;
     E.IsExpansion = true;
     new (&E.Expansion) ExpansionInfo(Expansion);
     return E;
   }
 };
 
 } // namespace SrcMgr
 
 /// External source of source location entries.
 class ExternalSLocEntrySource {
 public:
   virtual ~ExternalSLocEntrySource();
 
   /// Read the source location entry with index ID, which will always be
   /// less than -1.
   ///
   /// \returns true if an error occurred that prevented the source-location
   /// entry from being loaded.
   virtual bool ReadSLocEntry(int ID) = 0;
 
   /// Get the index ID for the loaded SourceLocation offset.
   ///
   /// \returns Invalid index ID (0) if an error occurred that prevented the
   /// SLocEntry  from being loaded.
   virtual int getSLocEntryID(SourceLocation::UIntTy SLocOffset) = 0;
 
   /// Retrieve the module import location and name for the given ID, if
   /// in fact it was loaded from a module (rather than, say, a precompiled
   /// header).
   virtual std::pair<SourceLocation, StringRef> getModuleImportLoc(int ID) = 0;
 };
 
 /// Holds the cache used by isBeforeInTranslationUnit.
 ///
 /// The cache structure is complex enough to be worth breaking out of
 /// SourceManager.
 class InBeforeInTUCacheEntry {
   /// The FileID's of the cached query.
   ///
   /// If these match up with a subsequent query, the result can be reused.
   FileID LQueryFID, RQueryFID;
 
   /// The relative order of FileIDs that the CommonFID *immediately* includes.
   ///
   /// This is used to compare macro expansion locations.
   bool LChildBeforeRChild;
 
   /// The file found in common between the two \#include traces, i.e.,
   /// the nearest common ancestor of the \#include tree.
   FileID CommonFID;
 
   /// The offset of the previous query in CommonFID.
   ///
   /// Usually, this represents the location of the \#include for QueryFID, but
   /// if LQueryFID is a parent of RQueryFID (or vice versa) then these can be a
   /// random token in the parent.
   unsigned LCommonOffset, RCommonOffset;
 
 public:
   InBeforeInTUCacheEntry() = default;
   InBeforeInTUCacheEntry(FileID L, FileID R) : LQueryFID(L), RQueryFID(R) {
     assert(L != R);
   }
 
   /// Return true if the currently cached values match up with
   /// the specified LHS/RHS query.
   ///
   /// If not, we can't use the cache.
   bool isCacheValid() const {
     return CommonFID.isValid();
   }
 
   /// If the cache is valid, compute the result given the
   /// specified offsets in the LHS/RHS FileID's.
   bool getCachedResult(unsigned LOffset, unsigned ROffset) const {
     // If one of the query files is the common file, use the offset.  Otherwise,
     // use the #include loc in the common file.
     if (LQueryFID != CommonFID) LOffset = LCommonOffset;
     if (RQueryFID != CommonFID) ROffset = RCommonOffset;
 
     // It is common for multiple macro expansions to be "included" from the same
     // location (expansion location), in which case use the order of the FileIDs
     // to determine which came first. This will also take care the case where
     // one of the locations points at the inclusion/expansion point of the other
     // in which case its FileID will come before the other.
     if (LOffset == ROffset)
       return LChildBeforeRChild;
 
     return LOffset < ROffset;
   }
 
   /// Set up a new query.
   /// If it matches the old query, we can keep the cached answer.
   void setQueryFIDs(FileID LHS, FileID RHS) {
     assert(LHS != RHS);
     if (LQueryFID != LHS || RQueryFID != RHS) {
       LQueryFID = LHS;
       RQueryFID = RHS;
       CommonFID = FileID();
     }
   }
 
   void setCommonLoc(FileID commonFID, unsigned lCommonOffset,
                     unsigned rCommonOffset, bool LParentBeforeRParent) {
     CommonFID = commonFID;
     LCommonOffset = lCommonOffset;
     RCommonOffset = rCommonOffset;
     LChildBeforeRChild = LParentBeforeRParent;
   }
 };
 
 /// The stack used when building modules on demand, which is used
 /// to provide a link between the source managers of the different compiler
 /// instances.
 using ModuleBuildStack = ArrayRef<std::pair<std::string, FullSourceLoc>>;
 
 /// This class handles loading and caching of source files into memory.
 ///
 /// This object owns the MemoryBuffer objects for all of the loaded
 /// files and assigns unique FileID's for each unique \#include chain.
 ///
 /// The SourceManager can be queried for information about SourceLocation
 /// objects, turning them into either spelling or expansion locations. Spelling
 /// locations represent where the bytes corresponding to a token came from and
 /// expansion locations represent where the location is in the user's view. In
 /// the case of a macro expansion, for example, the spelling location indicates
 /// where the expanded token came from and the expansion location specifies
 /// where it was expanded.
 class SourceManager : public RefCountedBase<SourceManager> {
   /// DiagnosticsEngine object.
   DiagnosticsEngine &Diag;
 
   FileManager &FileMgr;
 
   mutable llvm::BumpPtrAllocator ContentCacheAlloc;
 
   /// Memoized information about all of the files tracked by this
   /// SourceManager.
   ///
   /// This map allows us to merge ContentCache entries based
   /// on their FileEntry*.  All ContentCache objects will thus have unique,
   /// non-null, FileEntry pointers.
   llvm::DenseMap<FileEntryRef, SrcMgr::ContentCache*> FileInfos;
 
   /// True if the ContentCache for files that are overridden by other
   /// files, should report the original file name. Defaults to true.
   bool OverridenFilesKeepOriginalName = true;
 
   /// True if non-system source files should be treated as volatile
   /// (likely to change while trying to use them). Defaults to false.
   bool UserFilesAreVolatile;
 
   /// True if all files read during this compilation should be treated
   /// as transient (may not be present in later compilations using a module
   /// file created from this compilation). Defaults to false.
   bool FilesAreTransient = false;
 
   struct OverriddenFilesInfoTy {
     /// Files that have been overridden with the contents from another
     /// file.
     llvm::DenseMap<const FileEntry *, FileEntryRef> OverriddenFiles;
 
     /// Files that were overridden with a memory buffer.
     llvm::DenseSet<const FileEntry *> OverriddenFilesWithBuffer;
   };
 
   /// Lazily create the object keeping overridden files info, since
   /// it is uncommonly used.
   std::unique_ptr<OverriddenFilesInfoTy> OverriddenFilesInfo;
 
   OverriddenFilesInfoTy &getOverriddenFilesInfo() {
     if (!OverriddenFilesInfo)
       OverriddenFilesInfo.reset(new OverriddenFilesInfoTy);
     return *OverriddenFilesInfo;
   }
 
   /// Information about various memory buffers that we have read in.
   ///
   /// All FileEntry* within the stored ContentCache objects are NULL,
   /// as they do not refer to a file.
   std::vector<SrcMgr::ContentCache*> MemBufferInfos;
 
   /// The table of SLocEntries that are local to this module.
   ///
   /// Positive FileIDs are indexes into this table. Entry 0 indicates an invalid
   /// expansion.
   SmallVector<SrcMgr::SLocEntry, 0> LocalSLocEntryTable;
 
   /// The table of SLocEntries that are loaded from other modules.
   ///
   /// Negative FileIDs are indexes into this table. To get from ID to an index,
   /// use (-ID - 2).
   llvm::PagedVector<SrcMgr::SLocEntry, 32> LoadedSLocEntryTable;
 
   /// For each allocation in LoadedSLocEntryTable, we keep the first FileID.
   /// We assume exactly one allocation per AST file, and use that to determine
   /// whether two FileIDs come from the same AST file.
   SmallVector<FileID, 0> LoadedSLocEntryAllocBegin;
 
   /// The starting offset of the next local SLocEntry.
   ///
   /// This is LocalSLocEntryTable.back().Offset + the size of that entry.
   SourceLocation::UIntTy NextLocalOffset;
 
   /// The starting offset of the latest batch of loaded SLocEntries.
   ///
   /// This is LoadedSLocEntryTable.back().Offset, except that that entry might
   /// not have been loaded, so that value would be unknown.
   SourceLocation::UIntTy CurrentLoadedOffset;
 
   /// The highest possible offset is 2^31-1 (2^63-1 for 64-bit source
   /// locations), so CurrentLoadedOffset starts at 2^31 (2^63 resp.).
   static const SourceLocation::UIntTy MaxLoadedOffset =
       1ULL << (8 * sizeof(SourceLocation::UIntTy) - 1);
 
   /// A bitmap that indicates whether the entries of LoadedSLocEntryTable
   /// have already been loaded from the external source.
   ///
   /// Same indexing as LoadedSLocEntryTable.
   llvm::BitVector SLocEntryLoaded;
 
   /// A bitmap that indicates whether the entries of LoadedSLocEntryTable
   /// have already had their offset loaded from the external source.
   ///
   /// Superset of SLocEntryLoaded. Same indexing as SLocEntryLoaded.
   llvm::BitVector SLocEntryOffsetLoaded;
 
   /// An external source for source location entries.
   ExternalSLocEntrySource *ExternalSLocEntries = nullptr;
 
   /// A one-entry cache to speed up getFileID.
   ///
   /// LastFileIDLookup records the last FileID looked up or created, because it
   /// is very common to look up many tokens from the same file.
   mutable FileID LastFileIDLookup;
 
   /// Holds information for \#line directives.
   ///
   /// This is referenced by indices from SLocEntryTable.
   std::unique_ptr<LineTableInfo> LineTable;
 
   /// These ivars serve as a cache used in the getLineNumber
   /// method which is used to speedup getLineNumber calls to nearby locations.
   mutable FileID LastLineNoFileIDQuery;
   mutable const SrcMgr::ContentCache *LastLineNoContentCache;
   mutable unsigned LastLineNoFilePos;
   mutable unsigned LastLineNoResult;
 
   /// The file ID for the main source file of the translation unit.
   FileID MainFileID;
 
   /// The file ID for the precompiled preamble there is one.
   FileID PreambleFileID;
 
   // Statistics for -print-stats.
   mutable unsigned NumLinearScans = 0;
   mutable unsigned NumBinaryProbes = 0;
 
   /// Associates a FileID with its "included/expanded in" decomposed
   /// location.
   ///
   /// Used to cache results from and speed-up \c getDecomposedIncludedLoc
   /// function.
   mutable llvm::DenseMap<FileID, std::pair<FileID, unsigned>> IncludedLocMap;
 
   /// The key value into the IsBeforeInTUCache table.
   using IsBeforeInTUCacheKey = std::pair<FileID, FileID>;
 
   /// The IsBeforeInTranslationUnitCache is a mapping from FileID pairs
   /// to cache results.
   using InBeforeInTUCache =
       llvm::DenseMap<IsBeforeInTUCacheKey, InBeforeInTUCacheEntry>;
 
   /// Cache results for the isBeforeInTranslationUnit method.
   mutable InBeforeInTUCache IBTUCache;
   mutable InBeforeInTUCacheEntry IBTUCacheOverflow;
 
   /// Return the cache entry for comparing the given file IDs
   /// for isBeforeInTranslationUnit.
   InBeforeInTUCacheEntry &getInBeforeInTUCache(FileID LFID, FileID RFID) const;
 
   // Cache for the "fake" buffer used for error-recovery purposes.
   mutable std::unique_ptr<llvm::MemoryBuffer> FakeBufferForRecovery;
 
   mutable std::unique_ptr<SrcMgr::ContentCache> FakeContentCacheForRecovery;
 
   mutable std::unique_ptr<SrcMgr::SLocEntry> FakeSLocEntryForRecovery;
 
   /// Lazily computed map of macro argument chunks to their expanded
   /// source location.
   using MacroArgsMap = std::map<unsigned, SourceLocation>;
 
   mutable llvm::DenseMap<FileID, std::unique_ptr<MacroArgsMap>>
       MacroArgsCacheMap;
 
   /// The stack of modules being built, which is used to detect
   /// cycles in the module dependency graph as modules are being built, as
   /// well as to describe why we're rebuilding a particular module.
   ///
   /// There is no way to set this value from the command line. If we ever need
   /// to do so (e.g., if on-demand module construction moves out-of-process),
   /// we can add a cc1-level option to do so.
   SmallVector<std::pair<std::string, FullSourceLoc>, 2> StoredModuleBuildStack;
 
 public:
   SourceManager(DiagnosticsEngine &Diag, FileManager &FileMgr,
                 bool UserFilesAreVolatile = false);
   explicit SourceManager(const SourceManager &) = delete;
   SourceManager &operator=(const SourceManager &) = delete;
   ~SourceManager();
 
   void clearIDTables();
 
   /// Initialize this source manager suitably to replay the compilation
   /// described by \p Old. Requires that \p Old outlive \p *this.
   void initializeForReplay(const SourceManager &Old);
 
   DiagnosticsEngine &getDiagnostics() const { return Diag; }
 
   FileManager &getFileManager() const { return FileMgr; }
 
   /// Set true if the SourceManager should report the original file name
   /// for contents of files that were overridden by other files. Defaults to
   /// true.
   void setOverridenFilesKeepOriginalName(bool value) {
     OverridenFilesKeepOriginalName = value;
   }
 
   /// True if non-system source files should be treated as volatile
   /// (likely to change while trying to use them).
   bool userFilesAreVolatile() const { return UserFilesAreVolatile; }
 
   /// Retrieve the module build stack.
   ModuleBuildStack getModuleBuildStack() const {
     return StoredModuleBuildStack;
   }
 
   /// Set the module build stack.
   void setModuleBuildStack(ModuleBuildStack stack) {
     StoredModuleBuildStack.clear();
     StoredModuleBuildStack.append(stack.begin(), stack.end());
   }
 
   /// Push an entry to the module build stack.
   void pushModuleBuildStack(StringRef moduleName, FullSourceLoc importLoc) {
     StoredModuleBuildStack.push_back(std::make_pair(moduleName.str(),importLoc));
   }
 
   //===--------------------------------------------------------------------===//
   // MainFileID creation and querying methods.
   //===--------------------------------------------------------------------===//
 
   /// Returns the FileID of the main source file.
   FileID getMainFileID() const { return MainFileID; }
 
   /// Set the file ID for the main source file.
   void setMainFileID(FileID FID) {
     MainFileID = FID;
   }
 
   /// Returns true when the given FileEntry corresponds to the main file.
   ///
   /// The main file should be set prior to calling this function.
   bool isMainFile(const FileEntry &SourceFile);
 
   /// Set the file ID for the precompiled preamble.
   void setPreambleFileID(FileID Preamble) {
     assert(PreambleFileID.isInvalid() && "PreambleFileID already set!");
     PreambleFileID = Preamble;
   }
 
   /// Get the file ID for the precompiled preamble if there is one.
   FileID getPreambleFileID() const { return PreambleFileID; }
 
   //===--------------------------------------------------------------------===//
   // Methods to create new FileID's and macro expansions.
   //===--------------------------------------------------------------------===//
 
   /// Create a new FileID that represents the specified file
   /// being \#included from the specified IncludePosition.
   FileID createFileID(FileEntryRef SourceFile, SourceLocation IncludePos,
                       SrcMgr::CharacteristicKind FileCharacter,
                       int LoadedID = 0,
                       SourceLocation::UIntTy LoadedOffset = 0);
 
   /// 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 createFileID(std::unique_ptr<llvm::MemoryBuffer> Buffer,
                       SrcMgr::CharacteristicKind FileCharacter = SrcMgr::C_User,
                       int LoadedID = 0, SourceLocation::UIntTy LoadedOffset = 0,
                       SourceLocation IncludeLoc = SourceLocation());
 
   /// 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 createFileID(const llvm::MemoryBufferRef &Buffer,
                       SrcMgr::CharacteristicKind FileCharacter = SrcMgr::C_User,
                       int LoadedID = 0, SourceLocation::UIntTy LoadedOffset = 0,
                       SourceLocation IncludeLoc = SourceLocation());
 
   /// Get the FileID for \p SourceFile if it exists. Otherwise, create a
   /// new FileID for the \p SourceFile.
   FileID getOrCreateFileID(FileEntryRef SourceFile,
                            SrcMgr::CharacteristicKind FileCharacter);
 
   /// Creates an expansion SLocEntry for the substitution of an argument into a
   /// function-like macro's body. Returns the start of the expansion.
   ///
   /// The macro argument was written at \p SpellingLoc with length \p Length.
   /// \p ExpansionLoc is the parameter name in the (expanded) macro body.
   SourceLocation createMacroArgExpansionLoc(SourceLocation SpellingLoc,
                                             SourceLocation ExpansionLoc,
                                             unsigned Length);
 
   /// Creates an expansion SLocEntry for a macro use. Returns its start.
   ///
   /// The macro body begins at \p SpellingLoc with length \p Length.
   /// The macro use spans [ExpansionLocStart, ExpansionLocEnd].
   SourceLocation createExpansionLoc(SourceLocation SpellingLoc,
                                     SourceLocation ExpansionLocStart,
                                     SourceLocation ExpansionLocEnd,
                                     unsigned Length,
                                     bool ExpansionIsTokenRange = true,
                                     int LoadedID = 0,
                                     SourceLocation::UIntTy LoadedOffset = 0);
 
   /// Return a new SourceLocation that encodes that the token starting
   /// at \p TokenStart ends prematurely at \p TokenEnd.
   SourceLocation createTokenSplitLoc(SourceLocation SpellingLoc,
                                      SourceLocation TokenStart,
                                      SourceLocation TokenEnd);
 
   /// Retrieve the memory buffer associated with the given file.
   ///
   /// Returns std::nullopt if the buffer is not valid.
   std::optional<llvm::MemoryBufferRef>
   getMemoryBufferForFileOrNone(FileEntryRef File);
 
   /// Retrieve the memory buffer associated with the given file.
   ///
   /// Returns a fake buffer if there isn't a real one.
   llvm::MemoryBufferRef getMemoryBufferForFileOrFake(FileEntryRef File) {
     if (auto B = getMemoryBufferForFileOrNone(File))
       return *B;
     return getFakeBufferForRecovery();
   }
 
   /// Override the contents of the given source file by providing an
   /// already-allocated buffer.
   ///
   /// \param SourceFile the source file whose contents will be overridden.
   ///
   /// \param Buffer the memory buffer whose contents will be used as the
   /// data in the given source file.
   void overrideFileContents(FileEntryRef SourceFile,
                             const llvm::MemoryBufferRef &Buffer) {
     overrideFileContents(SourceFile, llvm::MemoryBuffer::getMemBuffer(Buffer));
   }
 
   /// Override the contents of the given source file by providing an
   /// already-allocated buffer.
   ///
   /// \param SourceFile the source file whose contents will be overridden.
   ///
   /// \param Buffer the memory buffer whose contents will be used as the
   /// data in the given source file.
   void overrideFileContents(FileEntryRef SourceFile,
                             std::unique_ptr<llvm::MemoryBuffer> Buffer);
 
   /// Override the given source file with another one.
   ///
   /// \param SourceFile the source file which will be overridden.
   ///
   /// \param NewFile the file whose contents will be used as the
   /// data instead of the contents of the given source file.
   void overrideFileContents(const FileEntry *SourceFile, FileEntryRef NewFile);
 
   /// Returns true if the file contents have been overridden.
   bool isFileOverridden(const FileEntry *File) const {
     if (OverriddenFilesInfo) {
       if (OverriddenFilesInfo->OverriddenFilesWithBuffer.count(File))
         return true;
       if (OverriddenFilesInfo->OverriddenFiles.contains(File))
         return true;
     }
     return false;
   }
 
   /// Bypass the overridden contents of a file.  This creates a new FileEntry
   /// and initializes the content cache for it.  Returns std::nullopt if there
   /// is no such file in the filesystem.
   ///
   /// This should be called before parsing has begun.
   OptionalFileEntryRef bypassFileContentsOverride(FileEntryRef File);
 
   /// Specify that a file is transient.
   void setFileIsTransient(FileEntryRef SourceFile);
 
   /// Specify that all files that are read during this compilation are
   /// transient.
   void setAllFilesAreTransient(bool Transient) {
     FilesAreTransient = Transient;
   }
 
   //===--------------------------------------------------------------------===//
   // FileID manipulation methods.
   //===--------------------------------------------------------------------===//
 
   /// Return the buffer for the specified FileID.
   ///
   /// If there is an error opening this buffer the first time, return
   /// std::nullopt.
   std::optional<llvm::MemoryBufferRef>
   getBufferOrNone(FileID FID, SourceLocation Loc = SourceLocation()) const {
     if (auto *Entry = getSLocEntryForFile(FID))
       return Entry->getFile().getContentCache().getBufferOrNone(
           Diag, getFileManager(), Loc);
     return std::nullopt;
   }
 
   /// Return the buffer for the specified FileID.
   ///
   /// If there is an error opening this buffer the first time, this
   /// manufactures a temporary buffer and returns it.
   llvm::MemoryBufferRef
   getBufferOrFake(FileID FID, SourceLocation Loc = SourceLocation()) const {
     if (auto B = getBufferOrNone(FID, Loc))
       return *B;
     return getFakeBufferForRecovery();
   }
 
   /// Returns the FileEntry record for the provided FileID.
   const FileEntry *getFileEntryForID(FileID FID) const {
     if (auto FE = getFileEntryRefForID(FID))
       return *FE;
     return nullptr;
   }
 
   /// Returns the FileEntryRef for the provided FileID.
   OptionalFileEntryRef getFileEntryRefForID(FileID FID) const {
     if (auto *Entry = getSLocEntryForFile(FID))
       return Entry->getFile().getContentCache().OrigEntry;
     return std::nullopt;
   }
 
   /// Returns the filename for the provided FileID, unless it's a built-in
   /// buffer that's not represented by a filename.
   ///
   /// Returns std::nullopt for non-files and built-in files.
   std::optional<StringRef> getNonBuiltinFilenameForID(FileID FID) const;
 
   /// Returns the FileEntry record for the provided SLocEntry.
   const FileEntry *
   getFileEntryForSLocEntry(const SrcMgr::SLocEntry &SLocEntry) const {
     if (auto FE = SLocEntry.getFile().getContentCache().OrigEntry)
       return *FE;
     return nullptr;
   }
 
   /// Return a StringRef to the source buffer data for the
   /// specified FileID.
   ///
   /// \param FID The file ID whose contents will be returned.
   /// \param Invalid If non-NULL, will be set true if an error occurred.
   StringRef getBufferData(FileID FID, bool *Invalid = nullptr) const;
 
   /// Return a StringRef to the source buffer data for the
   /// specified FileID, returning std::nullopt if invalid.
   ///
   /// \param FID The file ID whose contents will be returned.
   std::optional<StringRef> getBufferDataOrNone(FileID FID) const;
 
   /// Return a StringRef to the source buffer data for the
   /// specified FileID, returning std::nullopt if it's not yet loaded.
   ///
   /// \param FID The file ID whose contents will be returned.
   std::optional<StringRef> getBufferDataIfLoaded(FileID FID) const;
 
   /// Get the number of FileIDs (files and macros) that were created
   /// during preprocessing of \p FID, including it.
   unsigned getNumCreatedFIDsForFileID(FileID FID) const {
     if (auto *Entry = getSLocEntryForFile(FID))
       return Entry->getFile().NumCreatedFIDs;
     return 0;
   }
 
   /// Set the number of FileIDs (files and macros) that were created
   /// during preprocessing of \p FID, including it.
   void setNumCreatedFIDsForFileID(FileID FID, unsigned NumFIDs,
                                   bool Force = false) {
     auto *Entry = getSLocEntryForFile(FID);
     if (!Entry)
       return;
     assert((Force || Entry->getFile().NumCreatedFIDs == 0) && "Already set!");
     Entry->getFile().NumCreatedFIDs = NumFIDs;
   }
 
   //===--------------------------------------------------------------------===//
   // SourceLocation manipulation methods.
   //===--------------------------------------------------------------------===//
 
   /// Return the FileID for a SourceLocation.
   ///
   /// This is a very hot method that is used for all SourceManager queries
   /// that start with a SourceLocation object.  It is responsible for finding
   /// the entry in SLocEntryTable which contains the specified location.
   ///
   FileID getFileID(SourceLocation SpellingLoc) const {
     return getFileID(SpellingLoc.getOffset());
   }
 
   /// Return the filename of the file containing a SourceLocation.
   StringRef getFilename(SourceLocation SpellingLoc) const;
 
   /// Return the source location corresponding to the first byte of
   /// the specified file.
   SourceLocation getLocForStartOfFile(FileID FID) const {
     if (auto *Entry = getSLocEntryForFile(FID))
       return SourceLocation::getFileLoc(Entry->getOffset());
     return SourceLocation();
   }
 
   /// Return the source location corresponding to the last byte of the
   /// specified file.
   SourceLocation getLocForEndOfFile(FileID FID) const {
     if (auto *Entry = getSLocEntryForFile(FID))
       return SourceLocation::getFileLoc(Entry->getOffset() +
                                         getFileIDSize(FID));
     return SourceLocation();
   }
 
   /// Returns the include location if \p FID is a \#include'd file
   /// otherwise it returns an invalid location.
   SourceLocation getIncludeLoc(FileID FID) const {
     if (auto *Entry = getSLocEntryForFile(FID))
       return Entry->getFile().getIncludeLoc();
     return SourceLocation();
   }
 
   // Returns the import location if the given source location is
   // located within a module, or an invalid location if the source location
   // is within the current translation unit.
   std::pair<SourceLocation, StringRef>
   getModuleImportLoc(SourceLocation Loc) const {
     FileID FID = getFileID(Loc);
 
     // Positive file IDs are in the current translation unit, and -1 is a
     // placeholder.
     if (FID.ID >= -1)
       return std::make_pair(SourceLocation(), "");
 
     return ExternalSLocEntries->getModuleImportLoc(FID.ID);
   }
 
   /// Given a SourceLocation object \p Loc, return the expansion
   /// location referenced by the ID.
   SourceLocation getExpansionLoc(SourceLocation Loc) const {
     // Handle the non-mapped case inline, defer to out of line code to handle
     // expansions.
     if (Loc.isFileID()) return Loc;
     return getExpansionLocSlowCase(Loc);
   }
 
   /// Given \p Loc, if it is a macro location return the expansion
   /// location or the spelling location, depending on if it comes from a
   /// macro argument or not.
   SourceLocation getFileLoc(SourceLocation Loc) const {
     if (Loc.isFileID()) return Loc;
     return getFileLocSlowCase(Loc);
   }
 
   /// Return the start/end of the expansion information for an
   /// expansion location.
   ///
   /// \pre \p Loc is required to be an expansion location.
   CharSourceRange getImmediateExpansionRange(SourceLocation Loc) const;
 
   /// Given a SourceLocation object, return the range of
   /// tokens covered by the expansion in the ultimate file.
   CharSourceRange getExpansionRange(SourceLocation Loc) const;
 
   /// Given a SourceRange object, return the range of
   /// tokens or characters covered by the expansion in the ultimate file.
   CharSourceRange getExpansionRange(SourceRange Range) const {
     SourceLocation Begin = getExpansionRange(Range.getBegin()).getBegin();
     CharSourceRange End = getExpansionRange(Range.getEnd());
     return CharSourceRange(SourceRange(Begin, End.getEnd()),
                            End.isTokenRange());
   }
 
   /// Given a CharSourceRange object, return the range of
   /// tokens or characters covered by the expansion in the ultimate file.
   CharSourceRange getExpansionRange(CharSourceRange Range) const {
     CharSourceRange Expansion = getExpansionRange(Range.getAsRange());
     if (Expansion.getEnd() == Range.getEnd())
       Expansion.setTokenRange(Range.isTokenRange());
     return Expansion;
   }
 
   /// Given a SourceLocation object, return the spelling
   /// location referenced by the ID.
   ///
   /// This is the place where the characters that make up the lexed token
   /// can be found.
   SourceLocation getSpellingLoc(SourceLocation Loc) const {
     // Handle the non-mapped case inline, defer to out of line code to handle
     // expansions.
     if (Loc.isFileID()) return Loc;
     return getSpellingLocSlowCase(Loc);
   }
 
   /// Given a SourceLocation object, return the spelling location
   /// referenced by the ID.
   ///
   /// This is the first level down towards the place where the characters
   /// that make up the lexed token can be found.  This should not generally
   /// be used by clients.
   SourceLocation getImmediateSpellingLoc(SourceLocation Loc) const;
 
   /// Form a SourceLocation from a FileID and Offset pair.
   SourceLocation getComposedLoc(FileID FID, unsigned Offset) const {
     auto *Entry = getSLocEntryOrNull(FID);
     if (!Entry)
       return SourceLocation();
 
     SourceLocation::UIntTy GlobalOffset = Entry->getOffset() + Offset;
     return Entry->isFile() ? SourceLocation::getFileLoc(GlobalOffset)
                            : SourceLocation::getMacroLoc(GlobalOffset);
   }
 
   /// Decompose the specified location into a raw FileID + Offset pair.
   ///
   /// The first element is the FileID, the second is the offset from the
   /// start of the buffer of the location.
   std::pair<FileID, unsigned> getDecomposedLoc(SourceLocation Loc) const {
     FileID FID = getFileID(Loc);
     auto *Entry = getSLocEntryOrNull(FID);
     if (!Entry)
       return std::make_pair(FileID(), 0);
     return std::make_pair(FID, Loc.getOffset() - Entry->getOffset());
   }
 
   /// Decompose the specified location into a raw FileID + Offset pair.
   ///
   /// If the location is an expansion record, walk through it until we find
   /// the final location expanded.
   std::pair<FileID, unsigned>
   getDecomposedExpansionLoc(SourceLocation Loc) const {
     FileID FID = getFileID(Loc);
     auto *E = getSLocEntryOrNull(FID);
     if (!E)
       return std::make_pair(FileID(), 0);
 
     unsigned Offset = Loc.getOffset()-E->getOffset();
     if (Loc.isFileID())
       return std::make_pair(FID, Offset);
 
     return getDecomposedExpansionLocSlowCase(E);
   }
 
   /// Decompose the specified location into a raw FileID + Offset pair.
   ///
   /// If the location is an expansion record, walk through it until we find
   /// its spelling record.
   std::pair<FileID, unsigned>
   getDecomposedSpellingLoc(SourceLocation Loc) const {
     FileID FID = getFileID(Loc);
     auto *E = getSLocEntryOrNull(FID);
     if (!E)
       return std::make_pair(FileID(), 0);
 
     unsigned Offset = Loc.getOffset()-E->getOffset();
     if (Loc.isFileID())
       return std::make_pair(FID, Offset);
     return getDecomposedSpellingLocSlowCase(E, Offset);
   }
 
   /// Returns the "included/expanded in" decomposed location of the given
   /// FileID.
   std::pair<FileID, unsigned> getDecomposedIncludedLoc(FileID FID) const;
 
   /// Returns the offset from the start of the file that the
   /// specified SourceLocation represents.
   ///
   /// This is not very meaningful for a macro ID.
   unsigned getFileOffset(SourceLocation SpellingLoc) const {
     return getDecomposedLoc(SpellingLoc).second;
   }
 
   /// Tests whether the given source location represents a macro
   /// argument's expansion into the function-like macro definition.
   ///
   /// \param StartLoc If non-null and function returns true, it is set to the
   /// start location of the macro argument expansion.
   ///
   /// Such source locations only appear inside of the expansion
   /// locations representing where a particular function-like macro was
   /// expanded.
   bool isMacroArgExpansion(SourceLocation Loc,
                            SourceLocation *StartLoc = nullptr) const;
 
   /// Tests whether the given source location represents the expansion of
   /// a macro body.
   ///
   /// This is equivalent to testing whether the location is part of a macro
   /// expansion but not the expansion of an argument to a function-like macro.
   bool isMacroBodyExpansion(SourceLocation Loc) const;
 
   /// Returns true if the given MacroID location points at the beginning
   /// of the immediate macro expansion.
   ///
   /// \param MacroBegin If non-null and function returns true, it is set to the
   /// begin location of the immediate macro expansion.
   bool isAtStartOfImmediateMacroExpansion(SourceLocation Loc,
                                     SourceLocation *MacroBegin = nullptr) const;
 
   /// Returns true if the given MacroID location points at the character
   /// end of the immediate macro expansion.
   ///
   /// \param MacroEnd If non-null and function returns true, it is set to the
   /// character end location of the immediate macro expansion.
   bool
   isAtEndOfImmediateMacroExpansion(SourceLocation Loc,
                                    SourceLocation *MacroEnd = nullptr) const;
 
   /// Returns true if \p Loc is inside the [\p Start, +\p Length)
   /// chunk of the source location address space.
   ///
   /// If it's true and \p RelativeOffset is non-null, it will be set to the
   /// relative offset of \p Loc inside the chunk.
   bool
   isInSLocAddrSpace(SourceLocation Loc, SourceLocation Start, unsigned Length,
                     SourceLocation::UIntTy *RelativeOffset = nullptr) const {
     assert(((Start.getOffset() < NextLocalOffset &&
                Start.getOffset()+Length <= NextLocalOffset) ||
             (Start.getOffset() >= CurrentLoadedOffset &&
                 Start.getOffset()+Length < MaxLoadedOffset)) &&
            "Chunk is not valid SLoc address space");
     SourceLocation::UIntTy LocOffs = Loc.getOffset();
     SourceLocation::UIntTy BeginOffs = Start.getOffset();
     SourceLocation::UIntTy EndOffs = BeginOffs + Length;
     if (LocOffs >= BeginOffs && LocOffs < EndOffs) {
       if (RelativeOffset)
         *RelativeOffset = LocOffs - BeginOffs;
       return true;
     }
 
     return false;
   }
 
   /// Return true if both \p LHS and \p RHS are in the local source
   /// location address space or the loaded one.
   ///
   /// If it's true and \p RelativeOffset is non-null, it will be set to the
   /// offset of \p RHS relative to \p LHS.
   bool isInSameSLocAddrSpace(SourceLocation LHS, SourceLocation RHS,
                              SourceLocation::IntTy *RelativeOffset) const {
     SourceLocation::UIntTy LHSOffs = LHS.getOffset(), RHSOffs = RHS.getOffset();
     bool LHSLoaded = LHSOffs >= CurrentLoadedOffset;
     bool RHSLoaded = RHSOffs >= CurrentLoadedOffset;
 
     if (LHSLoaded == RHSLoaded) {
       if (RelativeOffset)
         *RelativeOffset = RHSOffs - LHSOffs;
       return true;
     }
 
     return false;
   }
 
   //===--------------------------------------------------------------------===//
   // Queries about the code at a SourceLocation.
   //===--------------------------------------------------------------------===//
 
   /// Return a pointer to the start of the specified location
   /// in the appropriate spelling MemoryBuffer.
   ///
   /// \param Invalid If non-NULL, will be set \c true if an error occurs.
   const char *getCharacterData(SourceLocation SL,
                                bool *Invalid = nullptr) const;
 
   /// Return the column # for the specified file position.
   ///
   /// This is significantly cheaper to compute than the line number.  This
   /// returns zero if the column number isn't known.  This may only be called
   /// on a file sloc, so you must choose a spelling or expansion location
   /// before calling this method.
   unsigned getColumnNumber(FileID FID, unsigned FilePos,
                            bool *Invalid = nullptr) const;
   unsigned getSpellingColumnNumber(SourceLocation Loc,
                                    bool *Invalid = nullptr) const;
   unsigned getExpansionColumnNumber(SourceLocation Loc,
                                     bool *Invalid = nullptr) const;
   unsigned getPresumedColumnNumber(SourceLocation Loc,
                                    bool *Invalid = nullptr) const;
 
   /// Given a SourceLocation, return the spelling line number
   /// for the position indicated.
   ///
   /// This requires building and caching a table of line offsets for the
   /// MemoryBuffer, so this is not cheap: use only when about to emit a
   /// diagnostic.
   unsigned getLineNumber(FileID FID, unsigned FilePos, bool *Invalid = nullptr) const;
   unsigned getSpellingLineNumber(SourceLocation Loc, bool *Invalid = nullptr) const;
   unsigned getExpansionLineNumber(SourceLocation Loc, bool *Invalid = nullptr) const;
   unsigned getPresumedLineNumber(SourceLocation Loc, bool *Invalid = nullptr) const;
 
   /// Return the filename or buffer identifier of the buffer the
   /// location is in.
   ///
   /// Note that this name does not respect \#line directives.  Use
   /// getPresumedLoc for normal clients.
   StringRef getBufferName(SourceLocation Loc, bool *Invalid = nullptr) const;
 
   /// Return the file characteristic of the specified source
   /// location, indicating whether this is a normal file, a system
   /// header, or an "implicit extern C" system header.
   ///
   /// This state can be modified with flags on GNU linemarker directives like:
   /// \code
   ///   # 4 "foo.h" 3
   /// \endcode
   /// which changes all source locations in the current file after that to be
   /// considered to be from a system header.
   SrcMgr::CharacteristicKind getFileCharacteristic(SourceLocation Loc) const;
 
   /// Returns the "presumed" location of a SourceLocation specifies.
   ///
   /// A "presumed location" can be modified by \#line or GNU line marker
   /// directives.  This provides a view on the data that a user should see
   /// in diagnostics, for example.
   ///
   /// Note that a presumed location is always given as the expansion point of
   /// an expansion location, not at the spelling location.
   ///
   /// \returns The presumed location of the specified SourceLocation. If the
   /// presumed location cannot be calculated (e.g., because \p Loc is invalid
   /// or the file containing \p Loc has changed on disk), returns an invalid
   /// presumed location.
   PresumedLoc getPresumedLoc(SourceLocation Loc,
                              bool UseLineDirectives = true) const;
 
   /// Returns whether the PresumedLoc for a given SourceLocation is
   /// in the main file.
   ///
   /// This computes the "presumed" location for a SourceLocation, then checks
   /// whether it came from a file other than the main file. This is different
   /// from isWrittenInMainFile() because it takes line marker directives into
   /// account.
   bool isInMainFile(SourceLocation Loc) const;
 
   /// Returns true if the spelling locations for both SourceLocations
   /// are part of the same file buffer.
   ///
   /// This check ignores line marker directives.
   bool isWrittenInSameFile(SourceLocation Loc1, SourceLocation Loc2) const {
     return getFileID(Loc1) == getFileID(Loc2);
   }
 
   /// Returns true if the spelling location for the given location
   /// is in the main file buffer.
   ///
   /// This check ignores line marker directives.
   bool isWrittenInMainFile(SourceLocation Loc) const {
     return getFileID(Loc) == getMainFileID();
   }
 
   /// Returns whether \p Loc is located in a <built-in> file.
   bool isWrittenInBuiltinFile(SourceLocation Loc) const {
     PresumedLoc Presumed = getPresumedLoc(Loc);
     if (Presumed.isInvalid())
       return false;
     StringRef Filename(Presumed.getFilename());
     return Filename == "<built-in>";
   }
 
   /// Returns whether \p Loc is located in a <command line> file.
   bool isWrittenInCommandLineFile(SourceLocation Loc) const {
     PresumedLoc Presumed = getPresumedLoc(Loc);
     if (Presumed.isInvalid())
       return false;
     StringRef Filename(Presumed.getFilename());
     return Filename == "<command line>";
   }
 
   /// Returns whether \p Loc is located in a <scratch space> file.
   bool isWrittenInScratchSpace(SourceLocation Loc) const {
     PresumedLoc Presumed = getPresumedLoc(Loc);
     if (Presumed.isInvalid())
       return false;
     StringRef Filename(Presumed.getFilename());
     return Filename == "<scratch space>";
   }
 
   /// Returns if a SourceLocation is in a system header.
   bool isInSystemHeader(SourceLocation Loc) const {
     if (Loc.isInvalid())
       return false;
     return isSystem(getFileCharacteristic(Loc));
   }
 
   /// Returns if a SourceLocation is in an "extern C" system header.
   bool isInExternCSystemHeader(SourceLocation Loc) const {
     return getFileCharacteristic(Loc) == SrcMgr::C_ExternCSystem;
   }
 
   /// Returns whether \p Loc is expanded from a macro in a system header.
   bool isInSystemMacro(SourceLocation loc) const {
     if (!loc.isMacroID())
       return false;
 
     // This happens when the macro is the result of a paste, in that case
     // its spelling is the scratch memory, so we take the parent context.
     // There can be several level of token pasting.
     if (isWrittenInScratchSpace(getSpellingLoc(loc))) {
       do {
         loc = getImmediateMacroCallerLoc(loc);
       } while (isWrittenInScratchSpace(getSpellingLoc(loc)));
       return isInSystemMacro(loc);
     }
 
     return isInSystemHeader(getSpellingLoc(loc));
   }
 
   /// The size of the SLocEntry that \p FID represents.
   unsigned getFileIDSize(FileID FID) const;
 
   /// Given a specific FileID, returns true if \p Loc is inside that
   /// FileID chunk and sets relative offset (offset of \p Loc from beginning
   /// of FileID) to \p relativeOffset.
   bool isInFileID(SourceLocation Loc, FileID FID,
                   unsigned *RelativeOffset = nullptr) const {
     SourceLocation::UIntTy Offs = Loc.getOffset();
     if (isOffsetInFileID(FID, Offs)) {
       if (RelativeOffset)
         *RelativeOffset = Offs - getSLocEntry(FID).getOffset();
       return true;
     }
 
     return false;
   }
 
   //===--------------------------------------------------------------------===//
   // Line Table Manipulation Routines
   //===--------------------------------------------------------------------===//
 
   /// Return the uniqued ID for the specified filename.
   unsigned getLineTableFilenameID(StringRef Str);
 
   /// Add a line note to the line table for the FileID and offset
   /// specified by Loc.
   ///
   /// If FilenameID is -1, it is considered to be unspecified.
   void AddLineNote(SourceLocation Loc, unsigned LineNo, int FilenameID,
                    bool IsFileEntry, bool IsFileExit,
                    SrcMgr::CharacteristicKind FileKind);
 
   /// Determine if the source manager has a line table.
   bool hasLineTable() const { return LineTable != nullptr; }
 
   /// Retrieve the stored line table.
   LineTableInfo &getLineTable();
 
   //===--------------------------------------------------------------------===//
   // Queries for performance analysis.
   //===--------------------------------------------------------------------===//
 
   /// Return the total amount of physical memory allocated by the
   /// ContentCache allocator.
   size_t getContentCacheSize() const {
     return ContentCacheAlloc.getTotalMemory();
   }
 
   struct MemoryBufferSizes {
     const size_t malloc_bytes;
     const size_t mmap_bytes;
 
     MemoryBufferSizes(size_t malloc_bytes, size_t mmap_bytes)
       : malloc_bytes(malloc_bytes), mmap_bytes(mmap_bytes) {}
   };
 
   /// Return the amount of memory used by memory buffers, breaking down
   /// by heap-backed versus mmap'ed memory.
   MemoryBufferSizes getMemoryBufferSizes() const;
 
   /// Return the amount of memory used for various side tables and
   /// data structures in the SourceManager.
   size_t getDataStructureSizes() const;
 
   //===--------------------------------------------------------------------===//
   // Other miscellaneous methods.
   //===--------------------------------------------------------------------===//
 
   /// Get the source location for the given file:line:col triplet.
   ///
   /// If the source file is included multiple times, the source location will
   /// be based upon the first inclusion.
   SourceLocation translateFileLineCol(const FileEntry *SourceFile,
                                       unsigned Line, unsigned Col) const;
 
   /// Get the FileID for the given file.
   ///
   /// If the source file is included multiple times, the FileID will be the
   /// first inclusion.
   FileID translateFile(const FileEntry *SourceFile) const;
   FileID translateFile(FileEntryRef SourceFile) const {
     return translateFile(&SourceFile.getFileEntry());
   }
 
   /// Get the source location in \p FID for the given line:col.
   /// Returns null location if \p FID is not a file SLocEntry.
   SourceLocation translateLineCol(FileID FID,
                                   unsigned Line, unsigned Col) const;
 
   /// If \p Loc points inside a function macro argument, the returned
   /// location will be the macro location in which the argument was expanded.
   /// If a macro argument is used multiple times, the expanded location will
   /// be at the first expansion of the argument.
   /// e.g.
   ///   MY_MACRO(foo);
   ///             ^
   /// Passing a file location pointing at 'foo', will yield a macro location
   /// where 'foo' was expanded into.
   SourceLocation getMacroArgExpandedLocation(SourceLocation Loc) const;
 
   /// Determines the order of 2 source locations in the translation unit.
   ///
   /// \returns true if LHS source location comes before RHS, false otherwise.
   bool isBeforeInTranslationUnit(SourceLocation LHS, SourceLocation RHS) const;
 
   /// Determines whether the two decomposed source location is in the
   ///        same translation unit. As a byproduct, it also calculates the order
   ///        of the source locations in case they are in the same TU.
   ///
   /// \returns Pair of bools the first component is true if the two locations
   ///          are in the same TU. The second bool is true if the first is true
   ///          and \p LOffs is before \p ROffs.
   std::pair<bool, bool>
   isInTheSameTranslationUnit(std::pair<FileID, unsigned> &LOffs,
                              std::pair<FileID, unsigned> &ROffs) const;
 
   /// \param Loc a source location in a loaded AST (of a PCH/Module file).
   /// \returns a FileID uniquely identifies the AST of a loaded
   /// module/PCH where `Loc` is at.
   FileID getUniqueLoadedASTFileID(SourceLocation Loc) const;
 
   /// Determines whether the two decomposed source location is in the same TU.
   bool isInTheSameTranslationUnitImpl(
       const std::pair<FileID, unsigned> &LOffs,
       const std::pair<FileID, unsigned> &ROffs) const;
 
   /// Determines the order of 2 source locations in the "source location
   /// address space".
   bool isBeforeInSLocAddrSpace(SourceLocation LHS, SourceLocation RHS) const {
     return isBeforeInSLocAddrSpace(LHS, RHS.getOffset());
   }
 
   /// Determines the order of a source location and a source location
   /// offset in the "source location address space".
   ///
   /// Note that we always consider source locations loaded from
   bool isBeforeInSLocAddrSpace(SourceLocation LHS,
                                SourceLocation::UIntTy RHS) const {
     SourceLocation::UIntTy LHSOffset = LHS.getOffset();
     bool LHSLoaded = LHSOffset >= CurrentLoadedOffset;
     bool RHSLoaded = RHS >= CurrentLoadedOffset;
     if (LHSLoaded == RHSLoaded)
       return LHSOffset < RHS;
 
     return LHSLoaded;
   }
 
   /// Return true if the Point is within Start and End.
   bool isPointWithin(SourceLocation Location, SourceLocation Start,
                      SourceLocation End) const {
     return Location == Start || Location == End ||
            (isBeforeInTranslationUnit(Start, Location) &&
             isBeforeInTranslationUnit(Location, End));
   }
 
   // Iterators over FileInfos.
   using fileinfo_iterator =
       llvm::DenseMap<FileEntryRef, SrcMgr::ContentCache *>::const_iterator;
 
   fileinfo_iterator fileinfo_begin() const { return FileInfos.begin(); }
   fileinfo_iterator fileinfo_end() const { return FileInfos.end(); }
   bool hasFileInfo(const FileEntry *File) const {
     return FileInfos.find_as(File) != FileInfos.end();
   }
 
   /// Print statistics to stderr.
   void PrintStats() const;
 
   void dump() const;
 
   // Produce notes describing the current source location address space usage.
   void noteSLocAddressSpaceUsage(DiagnosticsEngine &Diag,
                                  std::optional<unsigned> MaxNotes = 32) const;
 
   /// Get the number of local SLocEntries we have.
   unsigned local_sloc_entry_size() const { return LocalSLocEntryTable.size(); }
 
   /// Get a local SLocEntry. This is exposed for indexing.
   const SrcMgr::SLocEntry &getLocalSLocEntry(unsigned Index) const {
     return const_cast<SourceManager *>(this)->getLocalSLocEntry(Index);
   }
 
   /// Get a local SLocEntry. This is exposed for indexing.
   SrcMgr::SLocEntry &getLocalSLocEntry(unsigned Index) {
     assert(Index < LocalSLocEntryTable.size() && "Invalid index");
     return LocalSLocEntryTable[Index];
   }
 
   /// Get the number of loaded SLocEntries we have.
   unsigned loaded_sloc_entry_size() const { return LoadedSLocEntryTable.size();}
 
   /// Get a loaded SLocEntry. This is exposed for indexing.
   const SrcMgr::SLocEntry &getLoadedSLocEntry(unsigned Index,
                                               bool *Invalid = nullptr) const {
     return const_cast<SourceManager *>(this)->getLoadedSLocEntry(Index,
                                                                  Invalid);
   }
 
   /// Get a loaded SLocEntry. This is exposed for indexing.
   SrcMgr::SLocEntry &getLoadedSLocEntry(unsigned Index,
                                         bool *Invalid = nullptr) {
     assert(Index < LoadedSLocEntryTable.size() && "Invalid index");
     if (SLocEntryLoaded[Index])
       return LoadedSLocEntryTable[Index];
     return loadSLocEntry(Index, Invalid);
   }
 
   const SrcMgr::SLocEntry &getSLocEntry(FileID FID,
                                         bool *Invalid = nullptr) const {
     return const_cast<SourceManager *>(this)->getSLocEntry(FID, Invalid);
   }
 
   SrcMgr::SLocEntry &getSLocEntry(FileID FID, bool *Invalid = nullptr) {
     if (FID.ID == 0 || FID.ID == -1) {
       if (Invalid) *Invalid = true;
       return LocalSLocEntryTable[0];
     }
     return getSLocEntryByID(FID.ID, Invalid);
   }
 
   SourceLocation::UIntTy getNextLocalOffset() const { return NextLocalOffset; }
 
   void setExternalSLocEntrySource(ExternalSLocEntrySource *Source) {
     assert(LoadedSLocEntryTable.empty() &&
            "Invalidating existing loaded entries");
     ExternalSLocEntries = Source;
   }
 
   /// Allocate a number of loaded SLocEntries, which will be actually
   /// loaded on demand from the external source.
   ///
   /// NumSLocEntries will be allocated, which occupy a total of TotalSize space
   /// in the global source view. The lowest ID and the base offset of the
   /// entries will be returned.
   std::pair<int, SourceLocation::UIntTy>
   AllocateLoadedSLocEntries(unsigned NumSLocEntries,
                             SourceLocation::UIntTy TotalSize);
 
   /// Returns true if \p Loc came from a PCH/Module.
   bool isLoadedSourceLocation(SourceLocation Loc) const {
     return isLoadedOffset(Loc.getOffset());
   }
 
   /// Returns true if \p Loc did not come from a PCH/Module.
   bool isLocalSourceLocation(SourceLocation Loc) const {
     return isLocalOffset(Loc.getOffset());
   }
 
   /// Returns true if \p FID came from a PCH/Module.
   bool isLoadedFileID(FileID FID) const {
     assert(FID.ID != -1 && "Using FileID sentinel value");
     return FID.ID < 0;
   }
 
   /// Returns true if \p FID did not come from a PCH/Module.
   bool isLocalFileID(FileID FID) const {
     return !isLoadedFileID(FID);
   }
 
   /// Gets the location of the immediate macro caller, one level up the stack
   /// toward the initial macro typed into the source.
   SourceLocation getImmediateMacroCallerLoc(SourceLocation Loc) const {
     if (!Loc.isMacroID()) return Loc;
 
     // When we have the location of (part of) an expanded parameter, its
     // spelling location points to the argument as expanded in the macro call,
     // and therefore is used to locate the macro caller.
     if (isMacroArgExpansion(Loc))
       return getImmediateSpellingLoc(Loc);
 
     // Otherwise, the caller of the macro is located where this macro is
     // expanded (while the spelling is part of the macro definition).
     return getImmediateExpansionRange(Loc).getBegin();
   }
 
   /// \return Location of the top-level macro caller.
   SourceLocation getTopMacroCallerLoc(SourceLocation Loc) const;
 
 private:
   friend class ASTReader;
   friend class ASTWriter;
 
   llvm::MemoryBufferRef getFakeBufferForRecovery() const;
   SrcMgr::ContentCache &getFakeContentCacheForRecovery() const;
 
   const SrcMgr::SLocEntry &loadSLocEntry(unsigned Index, bool *Invalid) const;
   SrcMgr::SLocEntry &loadSLocEntry(unsigned Index, bool *Invalid);
 
   const SrcMgr::SLocEntry *getSLocEntryOrNull(FileID FID) const {
     return const_cast<SourceManager *>(this)->getSLocEntryOrNull(FID);
   }
 
   SrcMgr::SLocEntry *getSLocEntryOrNull(FileID FID) {
     bool Invalid = false;
     SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
     return Invalid ? nullptr : &Entry;
   }
 
   const SrcMgr::SLocEntry *getSLocEntryForFile(FileID FID) const {
     return const_cast<SourceManager *>(this)->getSLocEntryForFile(FID);
   }
 
   SrcMgr::SLocEntry *getSLocEntryForFile(FileID FID) {
     if (auto *Entry = getSLocEntryOrNull(FID))
       if (Entry->isFile())
         return Entry;
     return nullptr;
   }
 
   /// Get the entry with the given unwrapped FileID.
   /// Invalid will not be modified for Local IDs.
   const SrcMgr::SLocEntry &getSLocEntryByID(int ID,
                                             bool *Invalid = nullptr) const {
     return const_cast<SourceManager *>(this)->getSLocEntryByID(ID, Invalid);
   }
 
   SrcMgr::SLocEntry &getSLocEntryByID(int ID, bool *Invalid = nullptr) {
     assert(ID != -1 && "Using FileID sentinel value");
     if (ID < 0)
       return getLoadedSLocEntryByID(ID, Invalid);
     return getLocalSLocEntry(static_cast<unsigned>(ID));
   }
 
   const SrcMgr::SLocEntry &
   getLoadedSLocEntryByID(int ID, bool *Invalid = nullptr) const {
     return const_cast<SourceManager *>(this)->getLoadedSLocEntryByID(ID,
                                                                      Invalid);
   }
 
   SrcMgr::SLocEntry &getLoadedSLocEntryByID(int ID, bool *Invalid = nullptr) {
     return getLoadedSLocEntry(static_cast<unsigned>(-ID - 2), Invalid);
   }
 
   FileID getFileID(SourceLocation::UIntTy SLocOffset) const {
     // If our one-entry cache covers this offset, just return it.
     if (isOffsetInFileID(LastFileIDLookup, SLocOffset))
       return LastFileIDLookup;
 
     return getFileIDSlow(SLocOffset);
   }
 
   bool isLocalOffset(SourceLocation::UIntTy SLocOffset) const {
     return SLocOffset < CurrentLoadedOffset;
   }
 
   bool isLoadedOffset(SourceLocation::UIntTy SLocOffset) const {
     return SLocOffset >= CurrentLoadedOffset;
   }
 
   /// Implements the common elements of storing an expansion info struct into
   /// the SLocEntry table and producing a source location that refers to it.
   SourceLocation
   createExpansionLocImpl(const SrcMgr::ExpansionInfo &Expansion,
                          unsigned Length, int LoadedID = 0,
                          SourceLocation::UIntTy LoadedOffset = 0);
 
   /// Return true if the specified FileID contains the
   /// specified SourceLocation offset.  This is a very hot method.
   inline bool isOffsetInFileID(FileID FID,
                                SourceLocation::UIntTy SLocOffset) const {
     const SrcMgr::SLocEntry &Entry = getSLocEntry(FID);
     // If the entry is after the offset, it can't contain it.
     if (SLocOffset < Entry.getOffset()) return false;
 
     // If this is the very last entry then it does.
     if (FID.ID == -2)
       return true;
 
     // If it is the last local entry, then it does if the location is local.
     if (FID.ID+1 == static_cast<int>(LocalSLocEntryTable.size()))
       return SLocOffset < NextLocalOffset;
 
     // Otherwise, the entry after it has to not include it. This works for both
     // local and loaded entries.
     return SLocOffset < getSLocEntryByID(FID.ID+1).getOffset();
   }
 
   /// Returns the previous in-order FileID or an invalid FileID if there
   /// is no previous one.
   FileID getPreviousFileID(FileID FID) const;
 
   /// Returns the next in-order FileID or an invalid FileID if there is
   /// no next one.
   FileID getNextFileID(FileID FID) const;
 
   /// 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.
   FileID createFileIDImpl(SrcMgr::ContentCache &File, StringRef Filename,
                           SourceLocation IncludePos,
                           SrcMgr::CharacteristicKind DirCharacter, int LoadedID,
                           SourceLocation::UIntTy LoadedOffset);
 
   SrcMgr::ContentCache &getOrCreateContentCache(FileEntryRef SourceFile,
                                                 bool isSystemFile = false);
 
   /// Create a new ContentCache for the specified  memory buffer.
   SrcMgr::ContentCache &
   createMemBufferContentCache(std::unique_ptr<llvm::MemoryBuffer> Buf);
 
   FileID getFileIDSlow(SourceLocation::UIntTy SLocOffset) const;
   FileID getFileIDLocal(SourceLocation::UIntTy SLocOffset) const;
   FileID getFileIDLoaded(SourceLocation::UIntTy SLocOffset) const;
 
   SourceLocation getExpansionLocSlowCase(SourceLocation Loc) const;
   SourceLocation getSpellingLocSlowCase(SourceLocation Loc) const;
   SourceLocation getFileLocSlowCase(SourceLocation Loc) const;
 
   std::pair<FileID, unsigned>
   getDecomposedExpansionLocSlowCase(const SrcMgr::SLocEntry *E) const;
   std::pair<FileID, unsigned>
   getDecomposedSpellingLocSlowCase(const SrcMgr::SLocEntry *E,
                                    unsigned Offset) const;
   void computeMacroArgsCache(MacroArgsMap &MacroArgsCache, FileID FID) const;
   void associateFileChunkWithMacroArgExp(MacroArgsMap &MacroArgsCache,
                                          FileID FID,
                                          SourceLocation SpellLoc,
                                          SourceLocation ExpansionLoc,
                                          unsigned ExpansionLength) const;
   void updateSlocUsageStats() const;
 };
 
 /// Comparison function object.
 template<typename T>
 class BeforeThanCompare;
 
 /// Compare two source locations.
 template<>
 class BeforeThanCompare<SourceLocation> {
   SourceManager &SM;
 
 public:
   explicit BeforeThanCompare(SourceManager &SM) : SM(SM) {}
 
   bool operator()(SourceLocation LHS, SourceLocation RHS) const {
     return SM.isBeforeInTranslationUnit(LHS, RHS);
   }
 };
 
 /// Compare two non-overlapping source ranges.
 template<>
 class BeforeThanCompare<SourceRange> {
   SourceManager &SM;
 
 public:
   explicit BeforeThanCompare(SourceManager &SM) : SM(SM) {}
 
   bool operator()(SourceRange LHS, SourceRange RHS) const {
     return SM.isBeforeInTranslationUnit(LHS.getBegin(), RHS.getBegin());
   }
 };
 
 /// SourceManager and necessary dependencies (e.g. VFS, FileManager) for a
 /// single in-memorty file.
 class SourceManagerForFile {
 public:
   /// Creates SourceManager and necessary dependencies (e.g. VFS, FileManager).
   /// The main file in the SourceManager will be \p FileName with \p Content.
   SourceManagerForFile(StringRef FileName, StringRef Content);
 
   SourceManager &get() {
     assert(SourceMgr);
     return *SourceMgr;
   }
 
 private:
   // The order of these fields are important - they should be in the same order
   // as they are created in `createSourceManagerForFile` so that they can be
   // deleted in the reverse order as they are created.
   std::unique_ptr<FileManager> FileMgr;
   std::unique_ptr<DiagnosticsEngine> Diagnostics;
   std::unique_ptr<SourceManager> SourceMgr;
 };
 
 } // namespace clang
 
 #endif // LLVM_CLANG_BASIC_SOURCEMANAGER_H

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