(! code
'(left-shift
(popl %eax)         ; Pop value to be shifted into %EAX
(popl %ebx)         ; Pop shift amount value into %EBX
(andl %ebx %ebx)        ; checks to see if shift value is 0
(je escape)         ; jumps if so
(irmovl 1 %ecx)     ; moves the value 1 into %ECX so it can be used in subtraction
subloop
    (addl %eax %eax)    ; adds %EAX to itself, effectively multiplying by two, the equivilent of shifting left by 1
    (subl %ecx %ebx)    ; subtracts 1 from %EBX
    (andl %ebx %ebx)    ; checks to see if shift value is 0
    (jne subloop)       ; if non-zero, repeat loop
escape
(pushl %eax)        ; Push the final result on the stack.
))