[modules] When encoding SourceLocations in bitcode, rotate the 'is macro' flag

bit from the top bit to the bottom bit, so that we don't need 6 VBR6 hunks for
each macro location. Reduces libstdc++ module size by about 1%.

llvm-svn: 264540

clang/include/clang/Serialization/ASTReader.h

@@ -1979,9 +1979,15 @@ public:
   /// \brief Read the contents of a CXXCtorInitializer array.
   CXXCtorInitializer **GetExternalCXXCtorInitializers(uint64_t Offset) override;
 
+  /// \brief Read a source location from raw form and return it in its
+  /// originating module file's source location space.
+  SourceLocation ReadUntranslatedSourceLocation(uint32_t Raw) const {
+    return SourceLocation::getFromRawEncoding((Raw >> 1) | (Raw << 31));
+  }
+
   /// \brief Read a source location from raw form.
-  SourceLocation ReadSourceLocation(ModuleFile &ModuleFile, unsigned Raw) const {
-    SourceLocation Loc = SourceLocation::getFromRawEncoding(Raw);
+  SourceLocation ReadSourceLocation(ModuleFile &ModuleFile, uint32_t Raw) const {
+    SourceLocation Loc = ReadUntranslatedSourceLocation(Raw);
     return TranslateSourceLocation(ModuleFile, Loc);
   }
 

clang/lib/Serialization/ASTReader.cpp

@@ -2341,9 +2341,9 @@ ASTReader::ReadControlBlock(ModuleFile &F,
         ModuleKind ImportedKind = (ModuleKind)Record[Idx++];
         // The import location will be the local one for now; we will adjust
         // all import locations of module imports after the global source
-        // location info are setup.
+        // location info are setup, in ReadAST.
         SourceLocation ImportLoc =
-            SourceLocation::getFromRawEncoding(Record[Idx++]);
+            ReadUntranslatedSourceLocation(Record[Idx++]);
         off_t StoredSize = (off_t)Record[Idx++];
         time_t StoredModTime = (time_t)Record[Idx++];
         ASTFileSignature StoredSignature = Record[Idx++];
@@ -3601,11 +3601,12 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
 
     // Set the import location.
     F.DirectImportLoc = ImportLoc;
+    // FIXME: We assume that locations from PCH / preamble do not need
+    // any translation.
     if (!M->ImportedBy)
       F.ImportLoc = M->ImportLoc;
     else
-      F.ImportLoc = ReadSourceLocation(*M->ImportedBy,
-                                       M->ImportLoc.getRawEncoding());
+      F.ImportLoc = TranslateSourceLocation(*M->ImportedBy, M->ImportLoc);
   }
 
   if (!Context.getLangOpts().CPlusPlus ||
@@ -4982,7 +4983,6 @@ PreprocessedEntityID ASTReader::findNextPreprocessedEntity(
 
 namespace {
 
-template <unsigned PPEntityOffset::*PPLoc>
 struct PPEntityComp {
   const ASTReader &Reader;
   ModuleFile &M;
@@ -5006,7 +5006,7 @@ struct PPEntityComp {
   }
 
   SourceLocation getLoc(const PPEntityOffset &PPE) const {
-    return Reader.ReadSourceLocation(M, PPE.*PPLoc);
+    return Reader.TranslateSourceLocation(M, PPE.getBegin());
   }
 };
 
@@ -5037,7 +5037,7 @@ PreprocessedEntityID ASTReader::findPreprocessedEntity(SourceLocation Loc,
 
   if (EndsAfter) {
     PPI = std::upper_bound(pp_begin, pp_end, Loc,
-                           PPEntityComp<&PPEntityOffset::Begin>(*this, M));
+                           PPEntityComp(*this, M));
   } else {
     // Do a binary search manually instead of using std::lower_bound because
     // The end locations of entities may be unordered (when a macro expansion
@@ -5047,8 +5047,8 @@ PreprocessedEntityID ASTReader::findPreprocessedEntity(SourceLocation Loc,
       Half = Count / 2;
       PPI = First;
       std::advance(PPI, Half);
-      if (SourceMgr.isBeforeInTranslationUnit(ReadSourceLocation(M, PPI->End),
-                                              Loc)) {
+      if (SourceMgr.isBeforeInTranslationUnit(
+              TranslateSourceLocation(M, PPI->getEnd()), Loc)) {
         First = PPI;
         ++First;
         Count = Count - Half - 1;

clang/lib/Serialization/ASTWriter.cpp

@@ -1912,7 +1912,7 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
     Record.push_back(SLoc->getOffset() - 2);
     if (SLoc->isFile()) {
       const SrcMgr::FileInfo &File = SLoc->getFile();
-      Record.push_back(File.getIncludeLoc().getRawEncoding());
+      AddSourceLocation(File.getIncludeLoc(), Record);
       Record.push_back(File.getFileCharacteristic()); // FIXME: stable encoding
       Record.push_back(File.hasLineDirectives());
 
@@ -1984,10 +1984,12 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
     } else {
       // The source location entry is a macro expansion.
       const SrcMgr::ExpansionInfo &Expansion = SLoc->getExpansion();
-      Record.push_back(Expansion.getSpellingLoc().getRawEncoding());
-      Record.push_back(Expansion.getExpansionLocStart().getRawEncoding());
-      Record.push_back(Expansion.isMacroArgExpansion() ? 0
-                             : Expansion.getExpansionLocEnd().getRawEncoding());
+      AddSourceLocation(Expansion.getSpellingLoc(), Record);
+      AddSourceLocation(Expansion.getExpansionLocStart(), Record);
+      AddSourceLocation(Expansion.isMacroArgExpansion()
+                            ? SourceLocation()
+                            : Expansion.getExpansionLocEnd(),
+                        Record);
 
       // Compute the token length for this macro expansion.
       unsigned NextOffset = SourceMgr.getNextLocalOffset();
@@ -2669,7 +2671,7 @@ void ASTWriter::WritePragmaDiagnosticMappings(const DiagnosticsEngine &Diag,
     if (point.Loc.isInvalid())
       continue;
 
-    Record.push_back(point.Loc.getRawEncoding());
+    AddSourceLocation(point.Loc, Record);
     unsigned &DiagStateID = DiagStateIDMap[point.State];
     Record.push_back(DiagStateID);
     
@@ -4782,7 +4784,8 @@ void ASTWriter::WriteDeclUpdatesBlocks(RecordDataImpl &OffsetsRecord) {
 }
 
 void ASTWriter::AddSourceLocation(SourceLocation Loc, RecordDataImpl &Record) {
-  Record.push_back(Loc.getRawEncoding());
+  uint32_t Raw = Loc.getRawEncoding();
+  Record.push_back((Raw << 1) | (Raw >> 31));
 }
 
 void ASTWriter::AddSourceRange(SourceRange Range, RecordDataImpl &Record) {