Lazily declare default constructors. We now delay the construction of
declarations for implicit default constructors, copy constructors,
copy assignment operators, and destructors. On a "simple" translation
unit that includes a bunch of C++ standard library headers, we
generate relatively few of these implicit declarations now:

  4/159 implicit default constructors created
  18/236 implicit copy constructors created
  70/241 implicit copy assignment operators created
  0/173 implicit destructors created

And, on this translation unit, this optimization doesn't really
provide any benefit. I'll do some more performance measurements soon,
but this completes the implementation work for <rdar://problem/8151045>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107551 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index 1c41e5a..8020916 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -975,6 +975,12 @@
     CreateStoredDeclsMap(*C);
   }
 
+  // If there is an external AST source, load any declarations it knows about
+  // with this declaration's name.
+  if (ExternalASTSource *Source = getParentASTContext().getExternalSource())
+    if (hasExternalVisibleStorage())
+      Source->FindExternalVisibleDeclsByName(this, D->getDeclName());
+
   // Insert this declaration into the map.
   StoredDeclsList &DeclNameEntries = (*LookupPtr)[D->getDeclName()];
   if (DeclNameEntries.isNull()) {