Re: [avr-gcc-list] Avr-gcc Removing Port Register Access

[User Tomdean]

Here is a reduced application that reproduces the problem.  It may not
be minimal.

The compiler is 
#  avr-gcc --version
avr-gcc (GCC) 3.4.6


The command line is
# avr-gcc -mmcu=atmega8515 -Wall -Wmissing-prototypes \
     -Os -I. -c -S sbi-test.s sbi-test.c

In sbi-test.s, the two statements,
        sbi 59-0x20,6
        rjmp .L9
bracket the missing sbi.

If I change to -O, the missing sbi is included.

/*
 * sbi-test.c
 */
#include <avr/io.h>         /* port definitions */
#include <sbi-test.h>   /* local definitions */

void initialize() {
  LED_DDR  = 0xff;   /* all out */
  LED_PORT = 0xff;   /* all off */
  DDRC= 0;  /* all input */ 
  DDRE = 0x06;
  PORTD = 0x40;  /* PE[1]=0, PE[2]=1 */
  OSCCAL = 0x9c;   /* adjust for 8.000 mHz */
  UBRRL = 12;  /* 38400 at 8.000 mHz */
}

/*
 * main()
 */
int main() {
  char phase;
  initialize();
  LED_ON(7);
  LED_OFF(7);
  while (1) {
        LED_ON(7);

        LED_ON(3);
        while (!BIT_WAIT) {
        }
        LED_OFF(3);

        LED_ON(5);
        PORTE |=  _BV(PE1);
        PORTE &= ~_BV(PE1);
        PORTE &= ~_BV(PE2);
        phase = PINC;
        PORTE |=  _BV(PE2);
        LED_OFF(5);

        /*
         * reset the RCO2 counter
         */
        PORTD &= ~_BV(4);
        PORTD |=  _BV(4);

        LED_ON(6);
        while (BIT_WAIT) ;
        LED_OFF(6);
        LED_OFF(7); /* this is dropped */
  }
  return 0;
}
/*
 * sbi-test.h - Test gcc dropping sbi
 */

#ifndef _SBI_TEST_H_
#define  _SBI_TEST_H_

#define LED_PORT PORTA
#define LED_DDR  DDRA
#define LED_OFF(n) LED_PORT |=  _BV(n)
#define LED_ON(n)  LED_PORT &= ~_BV(n)

#define BIT_WAIT (PINE & _BV(PINE0))

void initialize(void);

#endif /* !_SBI_TEST_H_ */


tomdean