Index: lib/MC/MCParser/AsmParser.cpp
===================================================================
--- lib/MC/MCParser/AsmParser.cpp
+++ lib/MC/MCParser/AsmParser.cpp
@@ -3888,12 +3888,19 @@
 /// ::= .cfi_startproc [simple]
 bool AsmParser::parseDirectiveCFIStartProc() {
   StringRef Simple;
+  
   if (!parseOptionalToken(AsmToken::EndOfStatement)) {
     if (check(parseIdentifier(Simple) || Simple != "simple",
               "unexpected token") ||
         parseToken(AsmToken::EndOfStatement))
       return addErrorSuffix(" in '.cfi_startproc' directive");
   }
+  
+  // TODO(kristina): Deal with PP macro expansion so the error line
+  // matches the source chunk within the diagnostic when in a PP macro.
+  if (getStreamer().hasUnfinishedDwarfFrameInfo())
+    return Error(Lexer.getLoc(),
+                 ".cfi_startproc cannot be used in an existing frame");
 
   getStreamer().EmitCFIStartProc(!Simple.empty());
   return false;