Hello all,
I got portable WinAVR with avr-gcc version 4.3.2 and tried to compile simple
code:
/////////////////////////////// code
#include <avr/io.h>
#define XTALFQ (8e+6)
volatile unsigned char var0x55, var0xaa;
void delay_ms(unsigned int ms)
{
while(ms--) {
unsigned short int i;
for (i=100; i ; i-- ) {
unsigned short int b;
for(b=12*XTALFQ/12E6;b;b--) asm volatile("nop"::);
}
}
}
/************** main program ********************/
int main(void)
{
var0x55 = 0x55;
var0xaa = 0xaa;
/* INITIALIZE */
DDRC|= (1<<PC5);
PORTC|= (1<<PC5);
/* BLINK, BLINK ... */
while (1) {
/* invert PC5 */
PORTC ^= (1<<PC5);
// this code works
if ( (var0xaa ^ 0xff) == var0x55) {
delay_ms(100);
} else {
delay_ms(200);
}
// this code is buggy
if ( (~var0xaa) == var0x55) {
delay_ms(100);
} else {
delay_ms(200);
}
}
}
///////////////////////////////////////// end of code
The problem is with buggy code - when using '~', it gets expanded to 16 bits
(however, in avr-gcc 3.4.6 it was the same problem as well) :
// this code works
if ( (var0xaa ^ 0xff) == var0x55) {
84: 80 91 61 00 lds r24, 0x0061
88: 90 91 60 00 lds r25, 0x0060
8c: 80 95 com r24
8e: 89 17 cp r24, r25
90: f1 f4 brne .+60 ; 0xce <main+0x62>
92: 09 c0 rjmp .+18 ; 0xa6 <main+0x3a>
...
// this code is buggy
if ( (~var0xaa) == var0x55) {
e4: 80 91 61 00 lds r24, 0x0061
e8: 20 91 60 00 lds r18, 0x0060
ec: 90 e0 ldi r25, 0x00 ; 0
ee: 80 95 com r24
f0: 90 95 com r25
f2: 30 e0 ldi r19, 0x00 ; 0
f4: 82 17 cp r24, r18
f6: 93 07 cpc r25, r19
f8: f9 f4 brne .+62 ; 0x138 <main+0xcc>
fa: 09 c0 rjmp .+18 ; 0x10e <main+0xa2>
Furthermore, the new .LST file looks really crazy and the resulting code is
bigger ( 266 bytes from 4.3.2 compared to 130 bytes from 3.4.6).
Does anybody have a clue, what happened ?
Thank you in advance,
Vaclav
_______________________________________________
AVR-GCC-list mailing list
AVR-GCC-list@nongnu.org
http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
