addi $t0, $0, 42
j later
earlier:
addi $t1, $0, 4
sub $t2, $t0, $t1
or $t3, $t2, $t0
sw $t3, 0x2C($0) 
lw $t4, 0x28($t1) 
done:
j done
later:
beq $0, $0, earlier