Ensure that the identifier chains have the most recent declaration after module deserialization.

This commit introduces a set of related changes to ensure that the
declaration that shows up in the identifier chain after deserializing
declarations with a given identifier is, in fact, the most recent
declaration. The primary change involves waiting until after we
deserialize and wire up redeclaration chains before updating the
identifier chains. There is a minor optimization in here to avoid
recursively deserializing names as part of looking to see whether
top-level declarations for a given name exist.

A related change that became suddenly more urgent is to property
record a merged declaration when an entity first declared in the
current translation unit is later deserialized from a module (that had
not been loaded at the time of the original declaration). Since we key
off the canonical declaration (which is parsed, not from an AST file)
for emitted redeclarations, we simply record this as a merged
declaration during AST writing and let the readers merge them.

Re-fixes <rdar://problem/13189985>, presumably for good this time.

llvm-svn: 175447

1 files changed, 15 insertions, 3 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 79632b871a0..8747bc85122 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3141,20 +3141,32 @@ void ASTWriter::WriteRedeclarations() {
     LocalRedeclChains.push_back(0); // Placeholder for the size.
     
     // Collect the set of local redeclarations of this declaration.
-    for (Decl *Prev = MostRecent; Prev != First; 
+    for (Decl *Prev = MostRecent; Prev != First;
          Prev = Prev->getPreviousDecl()) { 
       if (!Prev->isFromASTFile()) {
         AddDeclRef(Prev, LocalRedeclChains);
         ++Size;
       }
     }
+
+    if (!First->isFromASTFile() && Chain) {
+      Decl *FirstFromAST = MostRecent;
+      for (Decl *Prev = MostRecent; Prev; Prev = Prev->getPreviousDecl()) {
+        if (Prev->isFromASTFile())
+          FirstFromAST = Prev;
+      }
+
+      Chain->MergedDecls[FirstFromAST].push_back(getDeclID(First));
+    }
+
     LocalRedeclChains[Offset] = Size;
     
     // Reverse the set of local redeclarations, so that we store them in
     // order (since we found them in reverse order).
     std::reverse(LocalRedeclChains.end() - Size, LocalRedeclChains.end());
     
-    // Add the mapping from the first ID to the set of local declarations.
+    // Add the mapping from the first ID from the AST to the set of local
+    // declarations.
     LocalRedeclarationsInfo Info = { getDeclID(First), Offset };
     LocalRedeclsMap.push_back(Info);
     
@@ -3807,8 +3819,8 @@ void ASTWriter::WriteASTCore(Sema &SemaRef,
   WriteMacroUpdates();
   WriteDeclUpdatesBlocks();
   WriteDeclReplacementsBlock();
-  WriteMergedDecls();
   WriteRedeclarations();
+  WriteMergedDecls();
   WriteObjCCategories();
   
   // Some simple statistics