4 files changed, 20 insertions, 1 deletions
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
index 26e0ecde15c..241c62e4ced 100644
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -288,7 +288,10 @@ namespace clang {
 
       /// \brief Record code for the module map file that was used to build this
       /// AST file.
-      MODULE_MAP_FILE = 14
+      MODULE_MAP_FILE = 14,
+
+      /// \brief Record code for the signature that identifiers this AST file.
+      SIGNATURE = 15
     };
 
     /// \brief Record types that occur within the input-files block
diff --git a/clang/include/clang/Serialization/ASTReader.h b/clang/include/clang/Serialization/ASTReader.h
index 730a257bca8..d967ec8d212 100644
--- a/clang/include/clang/Serialization/ASTReader.h
+++ b/clang/include/clang/Serialization/ASTReader.h
@@ -1125,6 +1125,7 @@ private:
                             SourceLocation ImportLoc, ModuleFile *ImportedBy,
                             SmallVectorImpl<ImportedModule> &Loaded,
                             off_t ExpectedSize, time_t ExpectedModTime,
+                            serialization::ASTFileSignature ExpectedSignature,
                             unsigned ClientLoadCapabilities);
   ASTReadResult ReadControlBlock(ModuleFile &F,
                                  SmallVectorImpl<ImportedModule> &Loaded,
diff --git a/clang/include/clang/Serialization/Module.h b/clang/include/clang/Serialization/Module.h
index a889e8b6540..f6889cfe8e1 100644
--- a/clang/include/clang/Serialization/Module.h
+++ b/clang/include/clang/Serialization/Module.h
@@ -97,6 +97,8 @@ public:
   bool isNotFound() const { return Val.getInt() == NotFound; }
 };
 
+typedef unsigned ASTFileSignature;
+
 /// \brief Information about a module that has been loaded by the ASTReader.
 ///
 /// Each instance of the Module class corresponds to a single AST file, which
@@ -152,6 +154,10 @@ public:
   /// \brief The file entry for the module file.
   const FileEntry *File;
 
+  /// \brief The signature of the module file, which may be used along with size
+  /// and modification time to identify this particular file.
+  ASTFileSignature Signature;
+
   /// \brief Whether this module has been directly imported by the
   /// user.
   bool DirectlyImported;
diff --git a/clang/include/clang/Serialization/ModuleManager.h b/clang/include/clang/Serialization/ModuleManager.h
index 96c3619510a..3d10fad0a1b 100644
--- a/clang/include/clang/Serialization/ModuleManager.h
+++ b/clang/include/clang/Serialization/ModuleManager.h
@@ -179,6 +179,12 @@ public:
   /// \param ExpectedModTime The expected modification time of the module
   /// file, used for validation. This will be zero if unknown.
   ///
+  /// \param ExpectedSignature The expected signature of the module file, used
+  /// for validation. This will be zero if unknown.
+  ///
+  /// \param ReadSignature Reads the signature from an AST file without actually
+  /// loading it.
+  ///
   /// \param Module A pointer to the module file if the module was successfully
   /// loaded.
   ///
@@ -191,6 +197,9 @@ public:
                             SourceLocation ImportLoc,
                             ModuleFile *ImportedBy, unsigned Generation,
                             off_t ExpectedSize, time_t ExpectedModTime,
+                            ASTFileSignature ExpectedSignature,
+                            std::function<ASTFileSignature(llvm::BitstreamReader &)>
+                                ReadSignature,
                             ModuleFile *&Module,
                             std::string &ErrorStr);