;-----------------------------------
; File: JVM2-0.a
; Author:  Dale Skrien
; Class:  CS232, Spring 2008
; This program reads in an integer x,
; calls the double function to compute
; 2*x, and outputs the result.
;-----------------------------------

n EQU 1      ; n will be local variable 1 for the double routine

;; main program
     iconst_0        ; push parameter 0 for the subroutine call
     input           ; input n & push onto the stack
     invokev double  ; call double
     output          ; output the result from the top of the stack
     stop            ; end the program

; This is the double function.
; Parameters: the unused 0th parameter and an integer n
; It returns 2*n on top of the stack
double:
     .data 1 2  ; # params on stack
     .data 1 2  ; # params + other local variables on stack
     iload n    ;load local variable 1 (that is, the value n)
     bipush 2   ;push the constant 2
     imul       ;multiply 2 and n
     ireturn    ;return 2*n to the caller