From c181a813e70bf3c1e8e1d3f32c5166561c610305 Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Sun, 27 Nov 2016 19:32:08 +0100
Subject: [PATCH] dda_queue.c: take advantage of a special case.

No functional change or stepping performance improvement, but a
14 bytes smaller binary:

  ATmega sizes               '168   '328(P)   '644(P)     '1280
  Program:  19426 bytes      136%       64%       31%       16%
     Data:   2177 bytes      213%      107%       54%       27%
   EEPROM:     32 bytes        4%        2%        2%        1%
---
 dda_queue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dda_queue.c b/dda_queue.c
index b039312..a77f5a9 100644
--- a/dda_queue.c
+++ b/dda_queue.c
@@ -139,7 +139,7 @@ void enqueue_home(TARGET *t, uint8_t endstop_check, uint8_t endstop_stop_cond) {
         version is inlined (and simplified) in queue_step().
       */
       timer_reset();
-      mb_tail = MB_NEXT(mb_tail);
+      mb_tail = mb_head;  // Valid ONLY if the queue was empty before!
       dda_start(&movebuffer[mb_tail]);
       // Compensate for the cli() in timer_set().
       sei();