Move prefix and suffix out of loop.

autoload/startuptime.vim

@@ -181,19 +181,19 @@ function! s:SetFile() abort
   " On Windows, to escape '[' with a backslash below, the character has to be
   " removed from 'isfname' (:help wilcard).
   set isfname-=[
+  " Prepend backslash to the prefix to avoid the special wildcard meaning
+  " (:help wildcard). Two backslashes are necessary on Windows, since Vim
+  " removes backslashes before special characters (:help dos-backslash).
+  " Issue #9.
+  let l:prefix = has('win32') ? '\\[' : '\['
+  let l:suffix = ']'
   let l:n = 0
   while 1
     try
       let l:text = 'startuptime'
       if l:n ># 0
         let l:text .= '.' . l:n
       endif
-      " Prepend backslash to the prefix to avoid the special wildcard meaning
-      " (:help wildcard). Two backslashes are necessary on Windows, since Vim
-      " removes backslashes before special characters (:help dos-backslash).
-      " Issue #9.
-      let l:prefix = has('win32') ? '\\[' : '\['
-      let l:suffix = ']'
       execute 'silent file ' . l:prefix . l:text . l:suffix
     catch
       let l:n += 1