add.c

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int32_t add_i32(int32_t a, int32_t b)
{
    int32_t result = 0;
    int overflow = 0;
    asm volatile (
        "mov %[a], %[result];"
        "add %[b], %[result];"
        : [overflow] "=@cco" (overflow), [result] "=r" (result)
        : [a] "r" (a), [b] "r" (b)
        : "cc"
    );

    if(overflow) {
        printf("Calculation overflowed!\n");
        exit(1);
    }

    return result;
}

int main(int argc, char **argv) {
    if(argc != 3) {
        printf("Usage: %s a b\n", argv[0]);
        exit(0);
    }
    int a = strtol(argv[1], NULL, 10), b = strtol(argv[2], NULL, 10);
    if(!a && !strcmp(argv[1], "0") || !b && !strcmp(argv[1], "0")) {
        printf("Please provide two non-zero numbers to add\n");
    }
    int32_t res = add_i32(a, b);
    printf("%d\n", res);
    return 0;
}