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

2 files changed, 40 insertions, 19 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index da29f69c7a1..e09af28059b 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -5533,27 +5533,16 @@ void ASTReader::ReadPragmaDiagnosticMappings(DiagnosticsEngine &Diag) {
       return NewState;
     };
 
+    // Read the first state.
     auto *FirstState = ReadDiagState(
         F.isModule() ? DiagState() : *Diag.DiagStatesByLoc.CurDiagState,
         SourceLocation(), F.isModule());
-    SourceLocation CurStateLoc =
-        ReadSourceLocation(F, F.PragmaDiagMappings[Idx++]);
-    auto *CurState = ReadDiagState(*FirstState, CurStateLoc, false);
 
-    if (!F.isModule()) {
-      Diag.DiagStatesByLoc.CurDiagState = CurState;
-      Diag.DiagStatesByLoc.CurDiagStateLoc = CurStateLoc;
-
-      // Preserve the property that the imaginary root file describes the
-      // current state.
-      auto &T = Diag.DiagStatesByLoc.Files[FileID()].StateTransitions;
-      if (T.empty())
-        T.push_back({CurState, 0});
-      else
-        T[0].State = CurState;
-    }
-
-    while (Idx < Record.size()) {
+    // Read the state transitions.
+    unsigned NumLocations = Record[Idx++];
+    while (NumLocations--) {
+      assert(Idx < Record.size() &&
+             "Invalid data, missing pragma diagnostic states");
       SourceLocation Loc = ReadSourceLocation(F, Record[Idx++]);
       auto IDAndOffset = SourceMgr.getDecomposedLoc(Loc);
       assert(IDAndOffset.second == 0 && "not a start location for a FileID");
@@ -5573,6 +5562,26 @@ void ASTReader::ReadPragmaDiagnosticMappings(DiagnosticsEngine &Diag) {
       }
     }
 
+    // Read the final state.
+    assert(Idx < Record.size() &&
+           "Invalid data, missing final pragma diagnostic state");
+    SourceLocation CurStateLoc =
+        ReadSourceLocation(F, F.PragmaDiagMappings[Idx++]);
+    auto *CurState = ReadDiagState(*FirstState, CurStateLoc, false);
+
+    if (!F.isModule()) {
+      Diag.DiagStatesByLoc.CurDiagState = CurState;
+      Diag.DiagStatesByLoc.CurDiagStateLoc = CurStateLoc;
+
+      // Preserve the property that the imaginary root file describes the
+      // current state.
+      auto &T = Diag.DiagStatesByLoc.Files[FileID()].StateTransitions;
+      if (T.empty())
+        T.push_back({CurState, 0});
+      else
+        T[0].State = CurState;
+    }
+
     // Don't try to read these mappings again.
     Record.clear();
   }
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);
 }