Silence a bunch of implicit fallthrough warnings

llvm-svn: 321115
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 55061aa..7ddab93 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -3116,7 +3116,8 @@
     if (DCE->getTypeAsWritten()->isReferenceType() &&
         DCE->getCastKind() == CK_Dynamic)
       return true;
-  } // Fall through.
+    }
+    LLVM_FALLTHROUGH;
   case ImplicitCastExprClass:
   case CStyleCastExprClass:
   case CXXStaticCastExprClass: