061e662345
Because of integer promotion the compiler is having a hard time generating
efficient code to calculate TIMER_DIFF* macros in some situations.
In the below example, the return value is "int", and this is causing the
trouble.
Example C code:
int __attribute__ ((noinline)) test(uint8_t current_timer, uint8_t start_timer)
{
return TIMER_DIFF_8(current_timer, start_timer);
}
BEFORE: (with -Os)
00004c40 <test>:
4c40: 28 2f mov r18, r24
4c42: 30 e0 ldi r19, 0x00 ; 0
4c44: 46 2f mov r20, r22
4c46: 50 e0 ldi r21, 0x00 ; 0
4c48: 86 17 cp r24, r22
4c4a: 20 f0 brcs .+8 ; 0x4c54 <test+0x14>
4c4c: c9 01 movw r24, r18
4c4e: 84 1b sub r24, r20
4c50: 95 0b sbc r25, r21
4c52: 08 95 ret
4c54: c9 01 movw r24, r18
4c56: 84 1b sub r24, r20
4c58: 95 0b sbc r25, r21
4c5a: 93 95 inc r25
4c5c: 08 95 ret
AFTER: (with -Os)
00004c40 <test>:
4c40: 86 1b sub r24, r22
4c42: 90 e0 ldi r25, 0x00 ; 0
4c44: 08 95 ret
Note: the example is showing -Os but improvements can be seen at all optimization levels,
including -O0. We never use -O0, but I tested it to make sure that no extra code is
generated in that case.
56 lines
1.6 KiB
C
56 lines
1.6 KiB
C
/*
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Copyright 2011 Jun Wako <wakojun@gmail.com>
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef TIMER_H
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#define TIMER_H 1
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#include <stdint.h>
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#if defined(__AVR__)
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#include "avr/timer_avr.h"
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#endif
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#define TIMER_DIFF(a, b, max) ((max == UINT8_MAX) ? ((uint8_t)((a)-(b))) : ( \
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(max == UINT16_MAX) ? ((uint16_t)((a)-(b))) : ( \
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(max == UINT32_MAX) ? ((uint32_t)((a)-(b))) : ( \
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(a) >= (b) ? (a) - (b) : (max) + 1 - (b) + (a) ))))
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#define TIMER_DIFF_8(a, b) TIMER_DIFF(a, b, UINT8_MAX)
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#define TIMER_DIFF_16(a, b) TIMER_DIFF(a, b, UINT16_MAX)
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#define TIMER_DIFF_32(a, b) TIMER_DIFF(a, b, UINT32_MAX)
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#define TIMER_DIFF_RAW(a, b) TIMER_DIFF_8(a, b)
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#ifdef __cplusplus
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extern "C" {
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#endif
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extern volatile uint32_t timer_count;
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void timer_init(void);
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void timer_clear(void);
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uint16_t timer_read(void);
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uint32_t timer_read32(void);
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uint16_t timer_elapsed(uint16_t last);
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uint32_t timer_elapsed32(uint32_t last);
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#ifdef __cplusplus
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}
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#endif
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#endif
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