/*
Bubble sort in ARM assembly

r0  data vector
r1  size of data

r3 pointer
r5 inner counter
r6 outer counter
r7 first element
r8 second element

r9 leds on
r10 leds off
r11  LEDs address

*/
.section .data
DataNum: .word 10
SortData: .word 0x7FFFFFF1, 0x7FFFFFFF, 0x00000000, 0x80000000, 0x80000001, 0xA1234332, 0x20141020, 0x6FFFFFFF, 0xA1234320, 0x20141F20

.text
.equ LEDs, 0xFF200000
.equ leds_on, 0xFFFFFFFF
.equ leds_off, 0x00000000
.equ element_size, 4 @ 4 byte words

.global _start
_start:

loadData:
    ldr r0, =SortData @ start of vector
    ldr r9, =DataNum
    ldr r1, [r9] @ r1 holds DataNum value


leds:
    ldr r9, =leds_on
    ldr r10, =leds_off
    ldr r11, =LEDs
	str r10, [r11] @ turn off leds


bubble:
    ldr r5,=1			@ inner counter
    ldr r6,=1			@ outer counter

    mov	r3, r0				@ initialize current pointer

    OuterLoop:
        cmp r6, r1
        beq EndOuterLoop

        InnerLoop:
            ldr	r7, [r3], #element_size		@ load one element
            ldr	r8, [r3]					@ load next one
            cmp	r7, r8						@ compare them
            bge	Swap						@ branch if the first one is greater

            sub	r3, r3, #element_size		@ reset pointer to the first element
            b CheckInnerLoopDone


        Swap:
            swp	r8, r8, [r3]				@ swap value in r8 with address in r4
            str	r8, [r3, #element_size]!	@ store new second element to incremented address

        CheckInnerLoopDone:
            add r5, r5, #1		    @ increment inner counter
            cmp r5, r1				@ check index variable
            bne	InnerLoop

        EndInnerLoop:
            cmp	r6, r1 				@ check index variable
            beq	EndOuterLoop

            ldr r5,=1				@ reset inner counter
            mov	r3, r0				@ reset pointer

            add r6, r6, #1			@ increment outer counter
            b	OuterLoop			@ start another iteration


    EndOuterLoop: str r9, [r11] @ turn on leds


STOP: B STOP /*Branch unconditionally to STOP*/


.end