Cache visibility of decls.

This unifies the linkage and visibility caching. I first implemented this when
working on pr13844, but the previous fixes removed the performance advantage of
this one.

This is still a step in the right direction for making linkage and visibility
cheap to use.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171048 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 22aad16..437e2a8 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -2147,8 +2147,11 @@
                                                       Deprecated.Version,
                                                       Obsoleted.Version,
                                                       IsUnavailable, Str);
-  if (NewAttr)
+  if (NewAttr) {
     D->addAttr(NewAttr);
+    NamedDecl *ND = cast<NamedDecl>(D);
+    ND->ClearLVCache();
+  }
 }
 
 VisibilityAttr *Sema::mergeVisibilityAttr(Decl *D, SourceRange Range,
@@ -2165,6 +2168,8 @@
     Diag(ExistingAttr->getLocation(), diag::err_mismatched_visibility);
     Diag(Range.getBegin(), diag::note_previous_attribute);
     D->dropAttr<VisibilityAttr>();
+    NamedDecl *ND = cast<NamedDecl>(D);
+    ND->ClearLVCache();
   }
   return ::new (Context) VisibilityAttr(Range, Context, Vis);
 }
@@ -2208,8 +2213,11 @@
   }
 
   VisibilityAttr *NewAttr = S.mergeVisibilityAttr(D, Attr.getRange(), type);
-  if (NewAttr)
+  if (NewAttr) {
     D->addAttr(NewAttr);
+    NamedDecl *ND = cast<NamedDecl>(D);
+    ND->ClearLVCache();
+  }
 }
 
 static void handleObjCMethodFamilyAttr(Sema &S, Decl *decl,