From 1326db002f582c0ad67b58d8a8744a9387e2dbca Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Mon, 21 Nov 2016 18:59:32 +0100
Subject: [PATCH] DDA, dda_step(): test for individual axes again.

This time we don't test for remaining steps, but wether the axis
moves at all. A much cheaper test, because this variable has to
be loaded into registers anyways.

Performance is now even better than without this test. Slowest
step down from 604 to 580 clock cycles.

  ATmega sizes               '168   '328(P)   '644(P)     '1280
  Program:  19610 bytes      137%       64%       31%       16%
     Data:   2175 bytes      213%      107%       54%       27%
   EEPROM:     32 bytes        4%        2%        2%        1%

  short-moves.gcode statistics:
  LED on occurences: 888.
  LED on time minimum: 280 clock cycles.
  LED on time maximum: 549 clock cycles.
  LED on time average: 286.273 clock cycles.

  smooth-curves.gcode statistics:
  LED on occurences: 23648.
  LED on time minimum: 272 clock cycles.
  LED on time maximum: 580 clock cycles.
  LED on time average: 307.439 clock cycles.

  triangle-odd.gcode statistics:
  LED on occurences: 1636.
  LED on time minimum: 272 clock cycles.
  LED on time maximum: 539 clock cycles.
  LED on time average: 297.732 clock cycles.
---
 dda.c | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/dda.c b/dda.c
index db3c17f..be43087 100644
--- a/dda.c
+++ b/dda.c
@@ -566,25 +566,33 @@ void dda_start(DDA *dda) {
 void dda_step(DDA *dda) {
 
   #if ! defined ACCELERATION_TEMPORAL
-    move_state.counter[X] -= dda->delta[X];
-    if (move_state.counter[X] < 0) {
-			x_step();
-      move_state.counter[X] += dda->total_steps;
+    if (dda->delta[X]) {
+      move_state.counter[X] -= dda->delta[X];
+      if (move_state.counter[X] < 0) {
+        x_step();
+        move_state.counter[X] += dda->total_steps;
+      }
 		}
-    move_state.counter[Y] -= dda->delta[Y];
-    if (move_state.counter[Y] < 0) {
-			y_step();
-      move_state.counter[Y] += dda->total_steps;
+    if (dda->delta[Y]) {
+      move_state.counter[Y] -= dda->delta[Y];
+      if (move_state.counter[Y] < 0) {
+        y_step();
+        move_state.counter[Y] += dda->total_steps;
+      }
 		}
-    move_state.counter[Z] -= dda->delta[Z];
-    if (move_state.counter[Z] < 0) {
-			z_step();
-      move_state.counter[Z] += dda->total_steps;
+    if (dda->delta[Z]) {
+      move_state.counter[Z] -= dda->delta[Z];
+      if (move_state.counter[Z] < 0) {
+        z_step();
+        move_state.counter[Z] += dda->total_steps;
+      }
 		}
-    move_state.counter[E] -= dda->delta[E];
-    if (move_state.counter[E] < 0) {
-			e_step();
-      move_state.counter[E] += dda->total_steps;
+    if (dda->delta[E]) {
+      move_state.counter[E] -= dda->delta[E];
+      if (move_state.counter[E] < 0) {
+        e_step();
+        move_state.counter[E] += dda->total_steps;
+      }
 		}
     move_state.step_no++;
   #endif