4 files changed, 22 insertions, 5 deletions
diff --git a/lib/Frontend/PCHReader.cpp b/lib/Frontend/PCHReader.cpp
index b916deaa69..fa6ad6f0a0 100644
--- a/lib/Frontend/PCHReader.cpp
+++ b/lib/Frontend/PCHReader.cpp
@@ -318,7 +318,11 @@ bool PCHReader::ReadPreprocessorBlock() {
     switch (RecType) {
     default:  // Default behavior: ignore unknown records.
       break;
-        
+    case pch::PP_COUNTER_VALUE:
+      if (!Record.empty())
+        PP.setCounterValue(Record[0]);
+      break;
+
     case pch::PP_MACRO_OBJECT_LIKE:
     case pch::PP_MACRO_FUNCTION_LIKE: {
       IdentifierInfo *II = DecodeIdentifierInfo(Record[0]);
diff --git a/lib/Frontend/PCHWriter.cpp b/lib/Frontend/PCHWriter.cpp
index 6faf37fb29..2cf932ce9b 100644
--- a/lib/Frontend/PCHWriter.cpp
+++ b/lib/Frontend/PCHWriter.cpp
@@ -567,6 +567,13 @@ void PCHWriter::WritePreprocessor(const Preprocessor &PP) {
   
   RecordData Record;
 
+  // If the preprocessor __COUNTER__ value has been bumped, remember it.
+  if (PP.getCounterValue() != 0) {
+    Record.push_back(PP.getCounterValue());
+    S.EmitRecord(pch::PP_COUNTER_VALUE, Record);
+    Record.clear();
+  }  
+  
   // Loop over all the macro definitions that are live at the end of the file,
   // emitting each to the PP section.
   // FIXME: Eventually we want to emit an index so that we can lazily load
@@ -627,9 +634,6 @@ void PCHWriter::WritePreprocessor(const Preprocessor &PP) {
     
   }
   
-  // TODO: someday when PP supports __COUNTER__, emit a record for its value if
-  // non-zero.
-  
   S.ExitBlock();
 }
 
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index b23311af19..797a5bf6f2 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -55,6 +55,7 @@ void Preprocessor::RegisterBuiltinMacros() {
   Ident__FILE__ = RegisterBuiltinMacro("__FILE__");
   Ident__DATE__ = RegisterBuiltinMacro("__DATE__");
   Ident__TIME__ = RegisterBuiltinMacro("__TIME__");
+  Ident__COUNTER__ = RegisterBuiltinMacro("__COUNTER__");
   Ident_Pragma  = RegisterBuiltinMacro("_Pragma");
   
   // GCC Extensions.
@@ -557,6 +558,13 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     TmpBuffer[Len] = '"';  // Replace the newline with a quote.
     Tok.setKind(tok::string_literal);
     CreateString(TmpBuffer, Len+1, Tok, Tok.getLocation());
+  } else if (II == Ident__COUNTER__) {
+    Diag(Tok, diag::ext_pp_counter);
+    
+    // __COUNTER__ expands to a simple numeric value.
+    sprintf(TmpBuffer, "%u", CounterValue++);
+    Tok.setKind(tok::numeric_constant);
+    CreateString(TmpBuffer, strlen(TmpBuffer), Tok, Tok.getLocation());
   } else {
     assert(0 && "Unknown identifier!");
   }
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index 097b4542b6..2c9b0b937a 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -53,7 +53,8 @@ Preprocessor::Preprocessor(Diagnostic &diags, const LangOptions &opts,
     SourceMgr(SM), HeaderInfo(Headers), Identifiers(opts, IILookup),
     CurPPLexer(0), CurDirLookup(0), Callbacks(0) {
   ScratchBuf = new ScratchBuffer(SourceMgr);
-
+  CounterValue = 0; // __COUNTER__ starts at 0.
+      
   // Clear stats.
   NumDirectives = NumDefined = NumUndefined = NumPragma = 0;
   NumIf = NumElse = NumEndif = 0;