[avr-gcc-list] Efficient I/O handling w. bitfields codegen problem

[Albert Seward]

I have some problems with code generation from GCC 3.3. Read my question
in the main block.

/*
 * bitfields.c
 *
 * GCC bitfields optimization test
 */
typedef union {
        unsigned char byte;
        struct {
                unsigned char pin0 : 1;
                unsigned char pin1 : 1;
                unsigned char pin2 : 1;
                unsigned char pin3 : 1;
                unsigned char pin4 : 1;
                unsigned char pin5 : 1;
                unsigned char pin6 : 1;
                unsigned char pin7 : 1;
        };
} volatile * const port_t;

port_t port[] = {(port_t)0x3d, (port_t)0x38, (port_t)0x35, (port_t)0x32};

// Another way...
struct  {
        port_t portA;
        port_t portB;
        port_t portC;
        port_t portD;
} ports = {(port_t)0x3d, (port_t)0x38, (port_t)0x35, (port_t)0x32};


int main(void) {
        /*  This works!
         *  It will give asm:
         *  cbi     0x18, 7
         */ sbi     0x18, 7
        port[1]->pin7 = 0;
        port[1]->pin7 = 1;

        /*  Why dont I get the same asm as above?
         *  Now I do get this:
         *
         *  lds     r30, 0x0068
         *  lds     r31, 0x0069
         *  ld      r24, Z
         *  andi    r24, 0x7F       ; 127
         *  st      Z, r24
         *
         *  lds     r30, 0x0068
         *  lds     r31, 0x0069
         *  ld      r24, Z
         *  ori     r24, 0x80       ; 128
         *  st      Z, r24
         *
         *  This is not as efficient, and it does not do the job
         *  if I for example want to change GIMSK this way.
         */
        ports.portA->pin7 = 0;
        ports.portA->pin7 = 1;

        for(;;)

        return 0;
}


Hope anyone has the time to help me. I am really stuck.