GCC erzeugt unlogischen Code

[s.frings]

Was das so gemeint, oder kann ich noch weiter optimieren?:

void __attribute__ ((naked)) TIMER0_COMP_vect (void)
{
   __asm__ __volatile (
      "push r0"            "\n\t"
      "in r0,__SREG__"     "\n\t"  // Sichere SREG in r0
      "dec r2"             "\n\t"  // --prescaler
      "brne return"        "\n\t"  // if (prescaler!=0) goto return:
          "push r24"       "\n\t"
          "sec"            "\n\t"  // system_time++
          "lds r24,%0"     "\n\t" 
          "adc r24,r2"     "\n\t"
          "sts %0,r24"     "\n\t"
          "lds r24,%0+1"   "\n\t"
          "adc r24,r2"     "\n\t"
          "sts %0+1,r24"   "\n\t"
          "lds r24,%0+2"   "\n\t"
          "adc r24,r2"     "\n\t"
          "sts %0+2,r24"   "\n\t"
          "lds r24,%0+3"   "\n\t"
          "adc r24,r2"     "\n\t"
          "sts %0+3,r24"   "\n\t"
          "ldi  r24,75"    "\n\t"  // prescaler=75
          "mov  r2,r24"    "\n\t"
          "pop r24"        "\n\t"
      "return:"            "\n\t"
      "out __SREG__,r0"    "\n\t"
      "pop r0"             "\n\t"
      "reti"               "\n\t"
      :: "i" (&system_time)
   );
}