MIPS shift left/shift right

Question

I'm teaching myself MIPS and came across this piece of code:

or $t0 $z0 $t1
srl $t0 1 $t0
sll $t0 1 $t0
sub $t0 $t0 $t1

the part here that interests me is that srl $t0 1 $t0 & sll $t0 1 $t0 is this correct? As i thought it would be srl $t0 $t0 1 with the n value last.

Also if $t1 contained 5, which is 00000101 when I do srl followed by sll would i just end up with something like this: 00000101

srl : 00000010
sll : 00000100

so $t0 would now be 4?

and then the sub part would be 5-4 which is 1?

Thanks in advance

Answer 1

Yes normally it has the form:

sll $t0 $t1 n

(or srl)

and yes you are right because logical shifts introduce 0's so your 5 would end up being a 4

and finally:

sub $t0 $t0 $t1

is equivalent to t0 = t0 - t1