gistfile1.txt

/* 
 * This is a demonstration of inline assembly for
 * the RISCV platform, written in C.
 */

#include <stdio.h>


int basicsum(int op1, int op2) {
    int result;
    asm volatile("add %[result], %[op1], %[op2]"    // AssemblerTemplate
            : [result] "=r" (result)                // OutputOperands
            : [op1] "r" (op1), [op2] "r" (op2)      // InputOperands
            );
    printf("\tbasicsum: %i+%i=%i\n", op1, op2, result);
    return result;
}


/*
 *  store value in address:
 *  first
 *  then load the address into temporary register t0 / x5
 *  then store the value to a memory location 0 + offset (t0)
 */
void storeword(int address, int value) {
    *(volatile int *)address = value;
}

int loadword(int address) {
    int result = *(volatile int *)address;
    printf("\tloadword: at %x, I see value %d\n", address, result);
    return result;
}


int main() {
    if (basicsum(5,4) == 9) {
        printf("basicsum\t\t...success!\n");
    }

    int data = 666;
    int target = 0;
    int *target_addr = &target;
    printf("storeword being passed value `%d` for address `%x`\n", 
            data, target_addr); 
    storeword(target_addr, data);
    if (loadword(target_addr) == data) {
        printf("load and store\t\t...success!\n");
    }
    return 0;
}