Index: tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
===================================================================
--- tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
+++ tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
@@ -75,7 +75,9 @@
 /// CurStreamTypeType - A type for CurStreamType
 enum CurStreamTypeType {
   UnknownBitstream,
-  LLVMIRBitstream
+  LLVMIRBitstream,
+  ClangSerializedASTBitstream,
+  ClangSerializedDiagnosticsBitstream,
 };
 
 }
@@ -791,17 +793,29 @@
   char Signature[6];
   Signature[0] = Stream.Read(8);
   Signature[1] = Stream.Read(8);
-  Signature[2] = Stream.Read(4);
-  Signature[3] = Stream.Read(4);
-  Signature[4] = Stream.Read(4);
-  Signature[5] = Stream.Read(4);
 
   // Autodetect the file contents, if it is one we know.
   CurStreamType = UnknownBitstream;
-  if (Signature[0] == 'B' && Signature[1] == 'C' &&
-      Signature[2] == 0x0 && Signature[3] == 0xC &&
-      Signature[4] == 0xE && Signature[5] == 0xD)
-    CurStreamType = LLVMIRBitstream;
+  if (Signature[0] == 'C' && Signature[1] == 'P') {
+    Signature[2] = Stream.Read(8);
+    Signature[3] = Stream.Read(8);
+    if (Signature[2] == 'C' && Signature[3] == 'H')
+      CurStreamType = ClangSerializedASTBitstream;
+  } else if (Signature[0] == 'D' && Signature[1] == 'I') {
+    Signature[2] = Stream.Read(8);
+    Signature[3] = Stream.Read(8);
+    if (Signature[2] == 'A' && Signature[3] == 'G')
+      CurStreamType = ClangSerializedDiagnosticsBitstream;
+  } else {
+    Signature[2] = Stream.Read(4);
+    Signature[3] = Stream.Read(4);
+    Signature[4] = Stream.Read(4);
+    Signature[5] = Stream.Read(4);
+    if (Signature[0] == 'B' && Signature[1] == 'C' &&
+        Signature[2] == 0x0 && Signature[3] == 0xC &&
+        Signature[4] == 0xE && Signature[5] == 0xD)
+      CurStreamType = LLVMIRBitstream;
+  }
 
   return false;
 }
@@ -870,8 +884,18 @@
   outs() << "\n";
   outs() << "        Stream type: ";
   switch (CurStreamType) {
-  case UnknownBitstream: outs() << "unknown\n"; break;
-  case LLVMIRBitstream:  outs() << "LLVM IR\n"; break;
+  case UnknownBitstream:
+    outs() << "unknown\n";
+    break;
+  case LLVMIRBitstream:
+    outs() << "LLVM IR\n";
+    break;
+  case ClangSerializedASTBitstream:
+    outs() << "Clang Serialized AST\n";
+    break;
+  case ClangSerializedDiagnosticsBitstream:
+    outs() << "Clang Serialized Diagnostics\n";
+    break;
   }
   outs() << "  # Toplevel Blocks: " << NumTopBlocks << "\n";
   outs() << "\n";