1 files changed, 16 insertions, 9 deletions

diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 8c14b5f395..36e1bb3a69 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -1796,10 +1796,12 @@ void ASTWriter::WritePreprocessor(const Preprocessor &PP, bool IsModule) {
   // Construct the list of macro definitions that need to be serialized.
   SmallVector<std::pair<const IdentifierInfo *, MacroInfo *>, 2> 
     MacrosToEmit;
+  llvm::SmallPtrSet<const IdentifierInfo*, 4> MacroDefinitionsSeen;
   for (Preprocessor::macro_iterator I = PP.macro_begin(Chain == 0),
                                     E = PP.macro_end(Chain == 0);
        I != E; ++I) {
     if (!IsModule || I->second->isPublic()) {
+      MacroDefinitionsSeen.insert(I->first);
       MacrosToEmit.push_back(std::make_pair(I->first, I->second));
     }
   }
@@ -1852,12 +1854,6 @@ void ASTWriter::WritePreprocessor(const Preprocessor &PP, bool IsModule) {
       Record.push_back(inferSubmoduleIDFromLocation(MI->getDefinitionLoc()));
       AddSourceLocation(MI->getDefinitionLoc(), Record);
       AddSourceLocation(MI->getDefinitionEndLoc(), Record);
-      MacroInfo *PrevMI = MI->getPreviousDefinition();
-      // Serialize only the part of the definition chain that is local.
-      // The chain will be synthesized across modules by the ASTReader.
-      if (Chain && PrevMI && PrevMI->isFromAST())
-        PrevMI = 0;
-      addMacroRef(PrevMI, Record);
       AddSourceLocation(MI->getUndefLoc(), Record);
       Record.push_back(MI->isUsed());
       Record.push_back(MI->isPublic());
@@ -2739,8 +2735,14 @@ public:
     if (isInterestingIdentifier(II, Macro)) {
       DataLen += 2; // 2 bytes for builtin ID
       DataLen += 2; // 2 bytes for flags
-      if (hadMacroDefinition(II, Macro))
+      if (hadMacroDefinition(II, Macro)) {
+        for (MacroInfo *M = Macro; M; M = M->getPreviousDefinition()) {
+          if (Writer.getMacroRef(M) != 0)
+            DataLen += 4;
+        }
+
         DataLen += 4;
+      }
 
       for (IdentifierResolver::iterator D = IdResolver.begin(II),
                                      DEnd = IdResolver.end();
@@ -2785,8 +2787,13 @@ public:
     clang::io::Emit16(Out, Bits);
 
     if (HadMacroDefinition) {
-      // Write the macro ID associated with this identifier.
-      clang::io::Emit32(Out, Writer.getMacroRef(Macro));
+      // Write all of the macro IDs associated with this identifier.
+      for (MacroInfo *M = Macro; M; M = M->getPreviousDefinition()) {
+        if (MacroID ID = Writer.getMacroRef(M))
+          clang::io::Emit32(Out, ID);
+      }
+
+      clang::io::Emit32(Out, 0);
     }
 
     // Emit the declaration IDs in reverse order, because the