Tweak Fdirectory_append for efficiency

* src/fileio.c (Fdirectory_append): Make slightly more efficient.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/fileio.c b/src/fileio.c
index a4f08383776..ddce4723f42 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -795,7 +795,8 @@ usage: (record DIRECTORY &rest COMPONENTS) */)
       for (i = 0; i < nargs; i++)
         {
           Lisp_Object arg = args[i];
-          if (STRING_MULTIBYTE (arg))
+          /* Use multibyte or all-ASCII strings as is. */
+          if (STRING_MULTIBYTE (arg) || SCHARS (arg) == SBYTES (arg))
             elements[i] = arg;
           else
             elements[i] = make_multibyte_string (SSDATA (arg), SCHARS (arg),