MIPS Assembly Examples with gcc

Simple function

       .globl    addfn;
        .type addfn, @function;
        .ent addfn
addfn:
        add $a0,$a0,$a1;

        move $v0,$a0;

        .end addfn;

        jr $ra;

Another Example

        .globl    myfn1;

        .type myfn1, @function;
        .ent myfn1
        .set reorder
myfn1:
        lw  $t9,16($sp);
        add $a0,$a0,$t9;
        add $a0,$a0,$a1;
        add $a0,$a0,$a2;
        add $a0,$a0,$a3;
 
        move $v0,$a0;
 
        .end myfn1;
 
        jr $ra;

Using the Functions

#include<stdio.h>
 
extern int myfn1(int,int,int,int,int);
extern int addfn(int,int);
 
int main()
{
 
    printf("hello world!!! %d\n",myfn1(1,2,3,4,5));
    return 1;
}

Example 3

        .globl    exe1;
        .type exe1, @function;
        .ent exe1
        .set reorder
exe1:
        move $t0,$a0;
        move $t1,$a1;
        li $v0,0;
loop:
        lw $t2,0($t0);
        add $v0,$v0,$t2;
        addi $t0,$t0,4;
        sub $t1,$t1,1;
        bnez $t1,loop;
        .end exe1;

        jr $ra;

System Call

       .globl    myfn1;
        .type myfn1, @function;
        .ent myfn1
        .set reorder
myfn1:
        li $v0,4020;
        syscall;        

        .end myfn1;

        jr $ra;

Inline Assembly

#include<stdio.h>
#include<unistd.h>

extern int myfn1();

int assemfunction(int x,int y)
{
    asm volatile (
            "add $v0,$a0,$a1"
    );
}

int add2(int x,int y)
{
    int z;
    asm volatile(
            "move $t1,%2\n\t"
            "add $t1,$t1,%1\n\t"
            "move %0,$t1"
            : "=r" (z)
            : "r" (x),"r" (y)
            : "t1"
            );
    return z;
}

void mymb()
{
    asm volatile(
            ".set push\n\t"
            ".set noreorder\n\t"
            ".set mips2\n\t"
            "sync\n\t"
            ".set pop"
            :::"memory");
}

int getpid2()
{
    asm volatile(
            "li $v0,4020\n\t"
            "syscall\n\t"
            );
}

int main()
{
    int f;
    int r,t,q;
    f=getpid2();
    t=getpid();
    printf("pid=%d pid2=%d\n",f,t);
    r=9;
    mymb();
    q=5;
    printf("res=%d\n",add2(5,8) );

    return 1;
}