/*
 *  Source name     : ex3_asmprog.s
 *  Executable name : ex3_asmprog
 *  Author          : Jason Fritts
 *  Description     : Compares two numbers and sets r0 to 1 if equal
 * 
 *  Build using these commands:
 *    as --gstabs ex1_asmprog.s -o ex1_asmprog.o
 *    gcc -g ex1_asmprog.o -o ex1_asmprog
 */

.text
.global main			// program entry point

main:
    push	{lr}		// Create stack frame
    push	{r6, r7}	// Save registers r6, r7

    // get value in variables 'a' and 'b'
    ldr		r6, =a
    ldrh	r6, [r6]
    ldr		r7, =b
    ldrh	r7, [r7]

    // start program code

    // initialize 'i' and 'result' values
    mov  r0, #0			// r0:  i = 0
    mov  r1, #0			// r1:  result = 0

    // iterate if loop count < b
  start_loop:
    cmp  r1, r6			// i < a ?
    bhs   end_loop

    add  r0, r0, r7		// result += b
    add  r1, r1, #1		// i++
    b   start_loop

  end_loop:
    // end program code
    pop		{r6, r7}	// Restore registers r6, r7
    pop		{pc}		// Exit & return control to OS


.section .rodata		// read-only (e.g. string) data

.section .data			// initialized data

a:
	.hword	3
b:
	.hword	8

.section .bss			// uninitialized data