Serialization: Emit the final diagnostic state last, almost NFC

Emit the final diagnostic state last to match source order.  This also
prepares for a follow-up commit for implicit modules.

There's no real functionaliy change, just a slightly different AST file
format.

llvm-svn: 300024

1 files changed, 14 insertions, 2 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index be1945d5715..ffcad78f295 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2888,13 +2888,18 @@ void ASTWriter::WritePragmaDiagnosticMappings(const DiagnosticsEngine &Diag,
   };
 
   AddDiagState(Diag.DiagStatesByLoc.FirstDiagState, isModule);
-  AddSourceLocation(Diag.DiagStatesByLoc.CurDiagStateLoc, Record);
-  AddDiagState(Diag.DiagStatesByLoc.CurDiagState, false);
 
+  // Reserve a spot for the number of locations with state transitions.
+  auto NumLocationsIdx = Record.size();
+  Record.emplace_back();
+
+  // Emit the state transitions.
+  unsigned NumLocations = 0;
   for (auto &FileIDAndFile : Diag.DiagStatesByLoc.Files) {
     if (!FileIDAndFile.first.isValid() ||
         !FileIDAndFile.second.HasLocalTransitions)
       continue;
+    ++NumLocations;
     AddSourceLocation(Diag.SourceMgr->getLocForStartOfFile(FileIDAndFile.first),
                       Record);
     Record.push_back(FileIDAndFile.second.StateTransitions.size());
@@ -2904,6 +2909,13 @@ void ASTWriter::WritePragmaDiagnosticMappings(const DiagnosticsEngine &Diag,
     }
   }
 
+  // Backpatch the number of locations.
+  Record[NumLocationsIdx] = NumLocations;
+
+  // Emit CurDiagStateLoc.  Do it last in order to match source order.
+  AddSourceLocation(Diag.DiagStatesByLoc.CurDiagStateLoc, Record);
+  AddDiagState(Diag.DiagStatesByLoc.CurDiagState, false);
+
   Stream.EmitRecord(DIAG_PRAGMA_MAPPINGS, Record);
 }