From: Keith Packard <keithp@keithp.com>
Date: Sat, 15 Jan 2011 20:25:57 +0000 (-0800)
Subject: altos: Optimize fetching of ADC data in flight code
X-Git-Tag: debian/0.8.1+71+gda42f40~1^2~2
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=2887fe7affc0706dbeb2f04df9a00a9b799903ed;hp=2681a17500913cbaf3966f09380bb1d6b59e3863

altos: Optimize fetching of ADC data in flight code

This stores the address of the desired sample in a local variable and
then fetches through that. Saves quite a few instructions.

Signed-off-by: Keith Packard <keithp@keithp.com>
---

diff --git a/src/ao_flight.c b/src/ao_flight.c
index 9eb9a014..637acd52 100644
--- a/src/ao_flight.c
+++ b/src/ao_flight.c
@@ -151,12 +151,14 @@ ao_flight(void)
 		while (ao_flight_adc != ao_adc_head) {
 			__pdata uint8_t ticks;
 			__pdata int16_t ao_vel_change;
+			__xdata struct ao_adc *ao_adc;
 			ao_flight_prev_tick = ao_flight_tick;
 
 			/* Capture a sample */
-			ao_raw_accel = ao_adc_ring[ao_flight_adc].accel;
-			ao_raw_pres = ao_adc_ring[ao_flight_adc].pres;
-			ao_flight_tick = ao_adc_ring[ao_flight_adc].tick;
+			ao_adc = &ao_adc_ring[ao_flight_adc];
+			ao_flight_tick = ao_adc->tick;
+			ao_raw_accel = ao_adc->accel;
+			ao_raw_pres = ao_adc->pres;
 
 			ao_flight_accel -= ao_flight_accel >> 4;
 			ao_flight_accel += ao_raw_accel >> 4;