[Modules] No transitive source location change

clang/include/clang/Basic/SourceLocation.h

@@ -90,6 +90,7 @@ class SourceLocation {
   friend class ASTWriter;
   friend class SourceManager;
   friend struct llvm::FoldingSetTrait<SourceLocation, void>;
+  friend class SourceLocationEncoding;
 
 public:
   using UIntTy = uint32_t;

clang/include/clang/Serialization/ASTBitCodes.h

@@ -23,6 +23,7 @@
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/OperatorKinds.h"
 #include "clang/Basic/SourceLocation.h"
+#include "clang/Serialization/SourceLocationEncoding.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/Bitstream/BitCodes.h"
 #include <cassert>
@@ -167,45 +168,38 @@ const unsigned int NUM_PREDEF_SUBMODULE_IDS = 1;
 
 /// Source range/offset of a preprocessed entity.
 struct PPEntityOffset {
+  using RawLocEncoding = SourceLocationEncoding::RawLocEncoding;
+
   /// Raw source location of beginning of range.
-  SourceLocation::UIntTy Begin;
+  RawLocEncoding Begin;
 
   /// Raw source location of end of range.
-  SourceLocation::UIntTy End;
+  RawLocEncoding End;
 
   /// Offset in the AST file relative to ModuleFile::MacroOffsetsBase.
   uint32_t BitOffset;
 
-  PPEntityOffset(SourceRange R, uint32_t BitOffset)
-      : Begin(R.getBegin().getRawEncoding()), End(R.getEnd().getRawEncoding()),
-        BitOffset(BitOffset) {}
-
-  SourceLocation getBegin() const {
-    return SourceLocation::getFromRawEncoding(Begin);
-  }
+  PPEntityOffset(RawLocEncoding Begin, RawLocEncoding End, uint32_t BitOffset)
+      : Begin(Begin), End(End), BitOffset(BitOffset) {}
 
-  SourceLocation getEnd() const {
-    return SourceLocation::getFromRawEncoding(End);
-  }
+  RawLocEncoding getBegin() const { return Begin; }
+  RawLocEncoding getEnd() const { return End; }
 };
 
 /// Source range of a skipped preprocessor region
 struct PPSkippedRange {
+  using RawLocEncoding = SourceLocationEncoding::RawLocEncoding;
+
   /// Raw source location of beginning of range.
-  SourceLocation::UIntTy Begin;
+  RawLocEncoding Begin;
   /// Raw source location of end of range.
-  SourceLocation::UIntTy End;
+  RawLocEncoding End;
 
-  PPSkippedRange(SourceRange R)
-      : Begin(R.getBegin().getRawEncoding()), End(R.getEnd().getRawEncoding()) {
-  }
+  PPSkippedRange(RawLocEncoding Begin, RawLocEncoding End)
+      : Begin(Begin), End(End) {}
 
-  SourceLocation getBegin() const {
-    return SourceLocation::getFromRawEncoding(Begin);
-  }
-  SourceLocation getEnd() const {
-    return SourceLocation::getFromRawEncoding(End);
-  }
+  RawLocEncoding getBegin() const { return Begin; }
+  RawLocEncoding getEnd() const { return End; }
 };
 
 /// Offset in the AST file. Use splitted 64-bit integer into low/high
@@ -231,26 +225,26 @@ struct UnderalignedInt64 {
 
 /// Source location and bit offset of a declaration.
 struct DeclOffset {
+  using RawLocEncoding = SourceLocationEncoding::RawLocEncoding;
+
   /// Raw source location.
-  SourceLocation::UIntTy Loc = 0;
+  RawLocEncoding RawLoc = 0;
 
   /// Offset relative to the start of the DECLTYPES_BLOCK block. Keep
   /// structure alignment 32-bit and avoid padding gap because undefined
   /// value in the padding affects AST hash.
   UnderalignedInt64 BitOffset;
 
   DeclOffset() = default;
-  DeclOffset(SourceLocation Loc, uint64_t BitOffset,
-             uint64_t DeclTypesBlockStartOffset) {
-    setLocation(Loc);
+  DeclOffset(RawLocEncoding RawLoc, uint64_t BitOffset,
+             uint64_t DeclTypesBlockStartOffset)
+      : RawLoc(RawLoc) {
     setBitOffset(BitOffset, DeclTypesBlockStartOffset);
   }
 
-  void setLocation(SourceLocation L) { Loc = L.getRawEncoding(); }
+  void setRawLoc(RawLocEncoding Loc) { RawLoc = Loc; }
 
-  SourceLocation getLocation() const {
-    return SourceLocation::getFromRawEncoding(Loc);
-  }
+  RawLocEncoding getRawLoc() const { return RawLoc; }
 
   void setBitOffset(uint64_t Offset, const uint64_t DeclTypesBlockStartOffset) {
     BitOffset.setBitOffset(Offset - DeclTypesBlockStartOffset);

clang/include/clang/Serialization/ASTReader.h

@@ -1771,6 +1771,7 @@ class ASTReader
 
   /// Retrieve the module manager.
   ModuleManager &getModuleManager() { return ModuleMgr; }
+  const ModuleManager &getModuleManager() const { return ModuleMgr; }
 
   /// Retrieve the preprocessor.
   Preprocessor &getPreprocessor() const { return PP; }
@@ -2177,8 +2178,8 @@ class ASTReader
 
   /// Retrieve the global submodule ID given a module and its local ID
   /// number.
-  serialization::SubmoduleID
-  getGlobalSubmoduleID(ModuleFile &M, unsigned LocalID);
+  serialization::SubmoduleID getGlobalSubmoduleID(ModuleFile &M,
+                                                  unsigned LocalID) const;
 
   /// Retrieve the submodule that corresponds to a global submodule ID.
   ///
@@ -2191,7 +2192,7 @@ class ASTReader
 
   /// Retrieve the module file with a given local ID within the specified
   /// ModuleFile.
-  ModuleFile *getLocalModuleFile(ModuleFile &M, unsigned ID);
+  ModuleFile *getLocalModuleFile(ModuleFile &M, unsigned ID) const;
 
   /// Get an ID for the given module file.
   unsigned getModuleFileID(ModuleFile *M);
@@ -2227,33 +2228,46 @@ class ASTReader
     return Sema::AlignPackInfo::getFromRawEncoding(Raw);
   }
 
+  using RawLocEncoding = SourceLocationEncoding::RawLocEncoding;
+
   /// Read a source location from raw form and return it in its
   /// originating module file's source location space.
-  SourceLocation ReadUntranslatedSourceLocation(SourceLocation::UIntTy Raw,
-                                                LocSeq *Seq = nullptr) const {
+  std::pair<SourceLocation, unsigned>
+  ReadUntranslatedSourceLocation(RawLocEncoding Raw,
+                                 LocSeq *Seq = nullptr) const {
     return SourceLocationEncoding::decode(Raw, Seq);
   }
 
   /// Read a source location from raw form.
-  SourceLocation ReadSourceLocation(ModuleFile &ModuleFile,
-                                    SourceLocation::UIntTy Raw,
+  SourceLocation ReadSourceLocation(ModuleFile &MF, RawLocEncoding Raw,
                                     LocSeq *Seq = nullptr) const {
-    SourceLocation Loc = ReadUntranslatedSourceLocation(Raw, Seq);
-    return TranslateSourceLocation(ModuleFile, Loc);
+    if (!MF.ModuleOffsetMap.empty())
+      ReadModuleOffsetMap(MF);
+
+    auto [Loc, ModuleFileIndex] = ReadUntranslatedSourceLocation(Raw, Seq);
+    ModuleFile *OwningModuleFile =
+        ModuleFileIndex == 0 ? &MF : MF.DependentModules[ModuleFileIndex - 1];
+
+    assert(!SourceMgr.isLoadedSourceLocation(Loc) &&
+           "Run out source location space");
+
+    return TranslateSourceLocation(*OwningModuleFile, Loc);
   }
 
   /// Translate a source location from another module file's source
   /// location space into ours.
   SourceLocation TranslateSourceLocation(ModuleFile &ModuleFile,
                                          SourceLocation Loc) const {
-    if (!ModuleFile.ModuleOffsetMap.empty())
-      ReadModuleOffsetMap(ModuleFile);
-    assert(ModuleFile.SLocRemap.find(Loc.getOffset()) !=
-               ModuleFile.SLocRemap.end() &&
-           "Cannot find offset to remap.");
-    SourceLocation::IntTy Remap =
-        ModuleFile.SLocRemap.find(Loc.getOffset())->second;
-    return Loc.getLocWithOffset(Remap);
+    if (Loc.isInvalid())
+      return Loc;
+
+    // FIXME: TranslateSourceLocation is not re-enterable. It is problematic
+    // to call TranslateSourceLocation on a translated source location.
+    // We either need a method to know whether or not a source location is
+    // translated or refactor the code to make it clear that
+    // TranslateSourceLocation won't be called with translated source location.
+
+    return Loc.getLocWithOffset(ModuleFile.SLocEntryBaseOffset - 2);
   }
 
   /// Read a source location.

clang/include/clang/Serialization/ASTWriter.h

@@ -666,6 +666,10 @@ class ASTWriter : public ASTDeserializationListener,
   void AddSourceLocation(SourceLocation Loc, RecordDataImpl &Record,
                          LocSeq *Seq = nullptr);
 
+  /// Return the raw encodings for source locations.
+  SourceLocationEncoding::RawLocEncoding
+  getRawSourceLocationEncoding(SourceLocation Loc, LocSeq *Seq = nullptr);
+
   /// Emit a source range.
   void AddSourceRange(SourceRange Range, RecordDataImpl &Record,
                       LocSeq *Seq = nullptr);

clang/include/clang/Serialization/ModuleFile.h

@@ -295,10 +295,6 @@ class ModuleFile {
   /// AST file.
   const uint32_t *SLocEntryOffsets = nullptr;
 
-  /// Remapping table for source locations in this module.
-  ContinuousRangeMap<SourceLocation::UIntTy, SourceLocation::IntTy, 2>
-      SLocRemap;
-
   // === Identifiers ===
 
   /// The number of identifiers in this AST file.
@@ -512,9 +508,17 @@ class ModuleFile {
   /// List of modules which depend on this module
   llvm::SetVector<ModuleFile *> ImportedBy;
 
-  /// List of modules which this module depends on
+  /// List of modules which this module directly imported
   llvm::SetVector<ModuleFile *> Imports;
 
+  /// List of modules which this modules dependent on. Different
+  /// from `Imports`, this includes indirectly imported modules too.
+  /// The order of DependentModules is significant. It should keep
+  /// the same order with that module file manager when we write
+  /// the current module file. The value of the member will be initialized
+  /// in `ASTReader::ReadModuleOffsetMap`.
+  llvm::SmallVector<ModuleFile *, 16> DependentModules;
+
   /// Determine whether this module was directly imported at
   /// any point during translation.
   bool isDirectlyImported() const { return DirectlyImported; }

clang/include/clang/Serialization/SourceLocationEncoding.h

@@ -6,28 +6,33 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Source locations are stored pervasively in the AST, making up a third of
-// the size of typical serialized files. Storing them efficiently is important.
+// We wish to encode the SourceLocation from other module file not dependent
+// on the other module file. So that the source location changes from other
+// module file may not affect the contents of the current module file. Then the
+// users don't need to recompile the whole project due to a new line in a module
+// unit in the root of the dependency graph.
 //
-// We use integers optimized by VBR-encoding, because:
-//  - when abbreviations cannot be used, VBR6 encoding is our only choice
-//  - in the worst case a SourceLocation can be ~any 32-bit number, but in
-//    practice they are highly predictable
+// To achieve this, we need to encode the index of the module file into the
+// encoding of the source location. The encoding of the source location may be:
 //
-// We encode the integer so that likely values encode as small numbers that
-// turn into few VBR chunks:
-//  - the invalid sentinel location is a very common value: it encodes as 0
-//  - the "macro or not" bit is stored at the bottom of the integer
-//    (rather than at the top, as in memory), so macro locations can have
-//    small representations.
-//  - related locations (e.g. of a left and right paren pair) are usually
-//    similar, so when encoding a sequence of locations we store only
-//    differences between successive elements.
+//      |-----------------------|-----------------------|
+//      |          A            |         B         | C |
+//
+//  * A: 32 bit. The index of the module file in the module manager + 1. The +1
+//  here is necessary since we wish 0 stands for the current module file.
+//  * B: 31 bit. The offset of the source location to the module file containing
+//  it.
+//  * C: The macro bit. We rotate it to the lowest bit so that we can save some
+//  space in case the index of the module file is 0.
+//
+// Specially, if the index of the module file is 0, we allow to encode a
+// sequence of locations we store only differences between successive elements.
 //
 //===----------------------------------------------------------------------===//
 
-#include <climits>
 #include "clang/Basic/SourceLocation.h"
+#include "llvm/Support/MathExtras.h"
+#include <climits>
 
 #ifndef LLVM_CLANG_SERIALIZATION_SOURCELOCATIONENCODING_H
 #define LLVM_CLANG_SERIALIZATION_SOURCELOCATIONENCODING_H
@@ -52,9 +57,13 @@ class SourceLocationEncoding {
   friend SourceLocationSequence;
 
 public:
-  static uint64_t encode(SourceLocation Loc,
-                         SourceLocationSequence * = nullptr);
-  static SourceLocation decode(uint64_t, SourceLocationSequence * = nullptr);
+  using RawLocEncoding = uint64_t;
+
+  static RawLocEncoding encode(SourceLocation Loc, UIntTy BaseOffset,
+                               unsigned BaseModuleFileIndex,
+                               SourceLocationSequence * = nullptr);
+  static std::pair<SourceLocation, unsigned>
+  decode(RawLocEncoding, SourceLocationSequence * = nullptr);
 };
 
 /// Serialized encoding of a sequence of SourceLocations.
@@ -149,14 +158,44 @@ class SourceLocationSequence::State {
   operator SourceLocationSequence *() { return &Seq; }
 };
 
-inline uint64_t SourceLocationEncoding::encode(SourceLocation Loc,
-                                               SourceLocationSequence *Seq) {
-  return Seq ? Seq->encode(Loc) : encodeRaw(Loc.getRawEncoding());
+inline SourceLocationEncoding::RawLocEncoding
+SourceLocationEncoding::encode(SourceLocation Loc, UIntTy BaseOffset,
+                               unsigned BaseModuleFileIndex,
+                               SourceLocationSequence *Seq) {
+  // If the source location is a local source location, we can try to optimize
+  // the similar sequences to only record the differences.
+  if (!BaseOffset)
+    return Seq ? Seq->encode(Loc) : encodeRaw(Loc.getRawEncoding());
+
+  if (Loc.isInvalid())
+    return 0;
+
+  // Otherwise, the higher bits are used to store the module file index,
+  // so it is meaningless to optimize the source locations into small
+  // integers. Let's try to always use the raw encodings.
+  assert(Loc.getOffset() >= BaseOffset);
+  Loc = Loc.getLocWithOffset(-BaseOffset);
+  RawLocEncoding Encoded = encodeRaw(Loc.getRawEncoding());
+
+  // 16 bits should be sufficient to store the module file index.
+  assert(BaseModuleFileIndex < (1 << 16));
+  Encoded |= (RawLocEncoding)BaseModuleFileIndex << 32;
+  return Encoded;
 }
-inline SourceLocation
-SourceLocationEncoding::decode(uint64_t Encoded, SourceLocationSequence *Seq) {
-  return Seq ? Seq->decode(Encoded)
-             : SourceLocation::getFromRawEncoding(decodeRaw(Encoded));
+inline std::pair<SourceLocation, unsigned>
+SourceLocationEncoding::decode(RawLocEncoding Encoded,
+                               SourceLocationSequence *Seq) {
+  unsigned ModuleFileIndex = Encoded >> 32;
+
+  if (!ModuleFileIndex)
+    return {Seq ? Seq->decode(Encoded)
+                : SourceLocation::getFromRawEncoding(decodeRaw(Encoded)),
+            ModuleFileIndex};
+
+  Encoded &= llvm::maskTrailingOnes<RawLocEncoding>(32);
+  SourceLocation Loc = SourceLocation::getFromRawEncoding(decodeRaw(Encoded));
+
+  return {Loc, ModuleFileIndex};
 }
 
 } // namespace clang

clang/lib/Frontend/ASTUnit.cpp

@@ -2374,8 +2374,6 @@ bool ASTUnit::serialize(raw_ostream &OS) {
   return serializeUnit(Writer, Buffer, getSema(), OS);
 }
 
-using SLocRemap = ContinuousRangeMap<unsigned, int, 2>;
-
 void ASTUnit::TranslateStoredDiagnostics(
                           FileManager &FileMgr,
                           SourceManager &SrcMgr,