la $t0, str
цикл: фунт $ t1,0 ($ t0)
beqz $t1,exit_loop## if $t1=0, exit
blt $t1,'a',no_change ## $t1 < a,next
bgt $t1,'z',no_change ## $t1 > z,next
addiu $t1,$t1,-32 ## convert to uppercase: 'A'-'a'=-32
sb $t1,0($t0)
no_change: addiu $ t0, $ t0,1 ## указатель приращения, i ++
j loop
exit_loop: