1 files changed, 40 insertions, 2 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index f3181546320..80b1c2b6bcc 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -2363,6 +2363,11 @@ ASTReader::ReadControlBlock(ModuleFile &F,
       break;
     }
 
+    case SIGNATURE:
+      assert((!F.Signature || F.Signature == Record[0]) && "signature changed");
+      F.Signature = Record[0];
+      break;
+
     case IMPORTS: {
       // Load each of the imported PCH files. 
       unsigned Idx = 0, N = Record.size();
@@ -2376,6 +2381,7 @@ ASTReader::ReadControlBlock(ModuleFile &F,
             SourceLocation::getFromRawEncoding(Record[Idx++]);
         off_t StoredSize = (off_t)Record[Idx++];
         time_t StoredModTime = (time_t)Record[Idx++];
+        ASTFileSignature StoredSignature = Record[Idx++];
         unsigned Length = Record[Idx++];
         SmallString<128> ImportedFile(Record.begin() + Idx,
                                       Record.begin() + Idx + Length);
@@ -2383,7 +2389,7 @@ ASTReader::ReadControlBlock(ModuleFile &F,
 
         // Load the AST file.
         switch(ReadASTCore(ImportedFile, ImportedKind, ImportLoc, &F, Loaded,
-                           StoredSize, StoredModTime,
+                           StoredSize, StoredModTime, StoredSignature,
                            ClientLoadCapabilities)) {
         case Failure: return Failure;
           // If we have to ignore the dependency, we'll have to ignore this too.
@@ -3552,7 +3558,7 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
   SmallVector<ImportedModule, 4> Loaded;
   switch(ASTReadResult ReadResult = ReadASTCore(FileName, Type, ImportLoc,
                                                 /*ImportedBy=*/nullptr, Loaded,
-                                                0, 0,
+                                                0, 0, 0,
                                                 ClientLoadCapabilities)) {
   case Failure:
   case Missing:
@@ -3719,6 +3725,8 @@ ASTReader::ASTReadResult ASTReader::ReadAST(const std::string &FileName,
   return Success;
 }
 
+static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile);
+
 ASTReader::ASTReadResult
 ASTReader::ReadASTCore(StringRef FileName,
                        ModuleKind Type,
@@ -3726,12 +3734,14 @@ ASTReader::ReadASTCore(StringRef FileName,
                        ModuleFile *ImportedBy,
                        SmallVectorImpl<ImportedModule> &Loaded,
                        off_t ExpectedSize, time_t ExpectedModTime,
+                       ASTFileSignature ExpectedSignature,
                        unsigned ClientLoadCapabilities) {
   ModuleFile *M;
   std::string ErrorStr;
   ModuleManager::AddModuleResult AddResult
     = ModuleMgr.addModule(FileName, Type, ImportLoc, ImportedBy,
                           getGeneration(), ExpectedSize, ExpectedModTime,
+                          ExpectedSignature, readASTFileSignature,
                           M, ErrorStr);
 
   switch (AddResult) {
@@ -4029,6 +4039,34 @@ static bool SkipCursorToBlock(BitstreamCursor &Cursor, unsigned BlockID) {
   }
 }
 
+static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile){
+  BitstreamCursor Stream(StreamFile);
+  if (Stream.Read(8) != 'C' ||
+      Stream.Read(8) != 'P' ||
+      Stream.Read(8) != 'C' ||
+      Stream.Read(8) != 'H') {
+    return 0;
+  }
+
+  // Scan for the CONTROL_BLOCK_ID block.
+  if (SkipCursorToBlock(Stream, CONTROL_BLOCK_ID))
+    return 0;
+
+  // Scan for SIGNATURE inside the control block.
+  ASTReader::RecordData Record;
+  while (1) {
+    llvm::BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
+    if (Entry.Kind == llvm::BitstreamEntry::EndBlock ||
+        Entry.Kind != llvm::BitstreamEntry::Record)
+      return 0;
+
+    Record.clear();
+    StringRef Blob;
+    if (SIGNATURE == Stream.readRecord(Entry.ID, Record, &Blob))
+      return Record[0];
+  }
+}
+
 /// \brief Retrieve the name of the original source file name
 /// directly from the AST file, without actually loading the AST
 /// file.