1 files changed, 7 insertions, 1 deletions
diff --git a/lib/Frontend/PCHWriter.cpp b/lib/Frontend/PCHWriter.cpp
index 4ac836419e..7eb398c166 100644
--- a/lib/Frontend/PCHWriter.cpp
+++ b/lib/Frontend/PCHWriter.cpp
@@ -2013,7 +2013,6 @@ public:
     EmitKeyDataLength(llvm::raw_ostream& Out, const IdentifierInfo* II, 
                       pch::IdentID ID) {
     unsigned KeyLen = strlen(II->getName()) + 1;
-    clang::io::Emit16(Out, KeyLen);
     unsigned DataLen = 4 + 4; // 4 bytes for token ID, builtin, flags
                               // 4 bytes for the persistent ID
     if (II->hasMacroDefinition() && 
@@ -2023,7 +2022,14 @@ public:
                                    DEnd = IdentifierResolver::end();
          D != DEnd; ++D)
       DataLen += sizeof(pch::DeclID);
+
+    // We emit the data length before the key length, because we want
+    // the key length to immediately precede the actual string
+    // data. This is so that our identifier length + key layout
+    // matches that of the identifier hash table for pretokenized
+    // headers.
     clang::io::Emit16(Out, DataLen);
+    clang::io::Emit16(Out, KeyLen);
     return std::make_pair(KeyLen, DataLen);
   }