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soft_pwm: avoid useless refetches of pwm_count

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The compiler is not able to reuse the value of pwm_count, but reloads it
on every evaluation, if is stored in a static variable, as it cannot prove
it will be unchanged. A variable with local scope may not be modified from
the outside, so its value can be reused.
Doing so reduces text size and instruction count.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
This commit is contained in:
Stefan Brüns 2017-03-14 20:24:17 +01:00 committed by Scott Lahteine
parent 35a55d5757
commit 0a74774af1
1 changed files with 19 additions and 17 deletions
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36
Marlin/temperature.cpp
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@ -1512,6 +1512,8 @@ void Temperature::isr() {
static uint8_t temp_count = 0;
static TempState temp_state = StartupDelay;
static uint8_t pwm_count = _BV(SOFT_PWM_SCALE);
// avoid multiple loads of pwm_count
uint8_t pwm_count_tmp = pwm_count;
// Static members for each heater
#if ENABLED(SLOW_PWM_HEATERS)
@ -1555,8 +1557,8 @@ void Temperature::isr() {
/**
* Standard PWM modulation
*/
if (pwm_count >= 127) {
pwm_count -= 127;
if (pwm_count_tmp >= 127) {
pwm_count_tmp -= 127;
soft_pwm_0 = (soft_pwm_0 & pwm_mask) + soft_pwm[0];
WRITE_HEATER_0(soft_pwm_0 > pwm_mask ? HIGH : LOW);
#if HOTENDS > 1
@ -1593,30 +1595,30 @@ void Temperature::isr() {
#endif
}
if (soft_pwm_0 <= pwm_count) WRITE_HEATER_0(0);
if (soft_pwm_0 <= pwm_count_tmp) WRITE_HEATER_0(0);
#if HOTENDS > 1
if (soft_pwm_1 <= pwm_count) WRITE_HEATER_1(0);
if (soft_pwm_1 <= pwm_count_tmp) WRITE_HEATER_1(0);
#if HOTENDS > 2
if (soft_pwm_2 <= pwm_count) WRITE_HEATER_2(0);
if (soft_pwm_2 <= pwm_count_tmp) WRITE_HEATER_2(0);
#if HOTENDS > 3
if (soft_pwm_3 <= pwm_count) WRITE_HEATER_3(0);
if (soft_pwm_3 <= pwm_count_tmp) WRITE_HEATER_3(0);
#endif
#endif
#endif
#if HAS_HEATER_BED
if (soft_pwm_BED <= pwm_count) WRITE_HEATER_BED(0);
if (soft_pwm_BED <= pwm_count_tmp) WRITE_HEATER_BED(0);
#endif
#if ENABLED(FAN_SOFT_PWM)
#if HAS_FAN0
if (soft_pwm_fan[0] <= pwm_count) WRITE_FAN(0);
if (soft_pwm_fan[0] <= pwm_count_tmp) WRITE_FAN(0);
#endif
#if HAS_FAN1
if (soft_pwm_fan[1] <= pwm_count) WRITE_FAN1(0);
if (soft_pwm_fan[1] <= pwm_count_tmp) WRITE_FAN1(0);
#endif
#if HAS_FAN2
if (soft_pwm_fan[2] <= pwm_count) WRITE_FAN2(0);
if (soft_pwm_fan[2] <= pwm_count_tmp) WRITE_FAN2(0);
#endif
#endif
@ -1628,7 +1630,7 @@ void Temperature::isr() {
// 3: / 16 = 61.0352 Hz
// 4: / 8 = 122.0703 Hz
// 5: / 4 = 244.1406 Hz
pwm_count += _BV(SOFT_PWM_SCALE);
pwm_count = pwm_count_tmp + _BV(SOFT_PWM_SCALE);
#else // SLOW_PWM_HEATERS
@ -1702,8 +1704,8 @@ void Temperature::isr() {
#endif
#if ENABLED(FAN_SOFT_PWM)
if (pwm_count >= 127) {
pwm_count = 0;
if (pwm_count_tmp >= 127) {
pwm_count_tmp = 0;
#if HAS_FAN0
soft_pwm_fan[0] = fanSpeedSoftPwm[0] >> 1;
WRITE_FAN(soft_pwm_fan[0] > 0 ? HIGH : LOW);
@ -1718,13 +1720,13 @@ void Temperature::isr() {
#endif
}
#if HAS_FAN0
if (soft_pwm_fan[0] <= pwm_count) WRITE_FAN(0);
if (soft_pwm_fan[0] <= pwm_count_tmp) WRITE_FAN(0);
#endif
#if HAS_FAN1
if (soft_pwm_fan[1] <= pwm_count) WRITE_FAN1(0);
if (soft_pwm_fan[1] <= pwm_count_tmp) WRITE_FAN1(0);
#endif
#if HAS_FAN2
if (soft_pwm_fan[2] <= pwm_count) WRITE_FAN2(0);
if (soft_pwm_fan[2] <= pwm_count_tmp) WRITE_FAN2(0);
#endif
#endif //FAN_SOFT_PWM
@ -1736,7 +1738,7 @@ void Temperature::isr() {
// 3: / 16 = 61.0352 Hz
// 4: / 8 = 122.0703 Hz
// 5: / 4 = 244.1406 Hz
pwm_count += _BV(SOFT_PWM_SCALE);
pwm_count = pwm_count_tmp + _BV(SOFT_PWM_SCALE);
// increment slow_pwm_count only every 64th pwm_count,
// i.e. yielding a PWM frequency of 16/128 Hz (8s).