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/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 105ef49..e1d772b 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1775,9 +1775,13 @@
                                     AA->getIntroduced(), AA->getDeprecated(),
                                     AA->getObsoleted(), AA->getUnavailable(),
                                     AA->getMessage());
-  else if (VisibilityAttr *VA = dyn_cast<VisibilityAttr>(Attr))
+  else if (VisibilityAttr *VA = dyn_cast<VisibilityAttr>(Attr)) {
     NewAttr = mergeVisibilityAttr(D, VA->getRange(), VA->getVisibility());
-  else if (DLLImportAttr *ImportA = dyn_cast<DLLImportAttr>(Attr))
+    if (NewAttr) {
+      NamedDecl *ND = cast<NamedDecl>(D);
+      ND->ClearLVCache();
+    }
+  } else if (DLLImportAttr *ImportA = dyn_cast<DLLImportAttr>(Attr))
     NewAttr = mergeDLLImportAttr(D, ImportA->getRange());
   else if (DLLExportAttr *ExportA = dyn_cast<DLLExportAttr>(Attr))
     NewAttr = mergeDLLExportAttr(D, ExportA->getRange());
@@ -6611,7 +6615,7 @@
     }
     VDecl->setTypeSourceInfo(DeducedType);
     VDecl->setType(DeducedType->getType());
-    VDecl->ClearLinkageCache();
+    VDecl->ClearLVCache();
     
     // In ARC, infer lifetime.
     if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(VDecl))