clock_divider_test.c

#include <stdio.h>

void type1(void);
void type2(void);
void type3(void);
void type4(void);

// CFlags for avr-gcc:
// -mmcu=atmega328p -DF_CPU=16000000UL -Os -funsigned-char -funsigned-bitfields
// -fpack-struct -fshort-enums -Wall -Wundef -MMD -MP

// avr-gcc 5.4.0: https://godbolt.org/z/vwbK4A
// avr-gcc 9.2.0: https://godbolt.org/z/CX9X2a
void type1(void)
{
    int i;
    printf("\n>>> Type 1: if(counter++ >= counter_max){...}");
    for(i = 8; i; i--){
        const unsigned char counter_max = 4;
        static unsigned char counter = 0;
        printf("\n%d", counter);
        if(counter++ >= counter_max-1){
            counter = 0;
            printf("-> IN");
        }
    }
}

// avr-gcc 5.4.0: https://godbolt.org/z/fg-FM5
// avr-gcc 9.2.0: https://godbolt.org/z/bQRP2E
void type2(void)
{
    int i;
    printf("\n>>> Type 2: if(++counter == counter_max){...}");
    for(i = 8; i; i--){
        const unsigned char counter_max = 4;
        static unsigned char counter = 0;
        printf("\n%d", counter);
        if(++counter == counter_max){
            counter = 0;
            printf("-> IN");
        }
    }
}

// avr-gcc 5.4.0: https://godbolt.org/z/_2zqR7
// avr-gcc 9.2.0: https://godbolt.org/z/evWgJD
void type3(void)
{
    int i;
    printf("\n>>> Type 3: if(!counter--){...}");
    for(i = 8; i; i--){
        const unsigned char counter_max = 4;
        static unsigned char counter = counter_max-1;
        printf("\n%d", counter);
        if(!counter--){
            counter = counter_max-1;
            printf("-> IN");
        }
    }
}

// avr-gcc 5.4.0: https://godbolt.org/z/XeXQmM
// avr-gcc 9.2.0: https://godbolt.org/z/ck7tzN
void type4(void)
{
    int i;
    printf("\n>>> Type 4: if(!--counter){...}");
    for(i = 8; i; i--){
        const unsigned char counter_max = 4;
        static unsigned char counter = counter_max;
        printf("\n%d", counter);
        if(!--counter){
            counter = counter_max;
            printf("-> IN");
        }
    }
}

int main(void)
{

    type1();
    type2();
    type3();
    type4();
}