Introduce a dummy volatile variable into the calculations involving volatile register variables. Performance will be impacted, but order will be maintained. For example, to fix the code attached to the issue: volatile uint32_t dummy = 0; volatile register uint32_t __R30; extern void timer_delay(uint32_t cycles); void main() {         timer_delay((58000 / 5) - 1);         do { REGNAME &= ~((0x00000002)+dummy); } while (0);         do { REGNAME |= ((0x00000008)+dummy); } while (0);         timer_delay((58000 / 5) - 1);         do { REGNAME &= ~((0x00000008)+dummy); } while (0);         do { REGNAME |= ((0x00000002)+dummy); } while (0);         ... /* Repeat */ }