; question - find all divisors of a number like 6, and store in data memory. find if number is perfect or not. if sum of divisors is the number itself, then perfect. if perfect, store FF next to divisor list, otherwise store 11
; this version includes branching and works properly.

		AREA RESET, DATA, READONLY
        EXPORT __Vectors
__Vectors
        DCD 0x10001000
        DCD Reset_Handler
        ALIGN

        AREA MYCODE, CODE, READONLY
        ENTRY
        EXPORT Reset_Handler

Reset_Handler
        LDR R0, =9
        LDR R1, =0x10001000
        BL DivisorsSum
        MOV R2, R0
        MOV R3, R1
        LDR R4, =9
        CMP R2, R4
        BNE not_perfect
        LDR R5, =0x000000FF
        STR R5, [R3]
        B STOP
not_perfect
        LDR R5, =0x00000011
        STR R5, [R3]
STOP
        B STOP

DivisorsSum
        PUSH{R4-R7, LR}
        MOV R6, R0
        MOV R7, R1
        MOV R5, #0
        LSRS R3, R6, #1
        MOV R4, #1
div_loop
        CMP R4, R3
        BGT div_end
        MOV R0, R6
        MOV R1, R4
        BL IsDivisible
        CMP R0, #1
        BNE div_skip
        STR R4, [R7], #4
        ADD R5, R5, R4
div_skip
        ADD R4, R4, #1
        B div_loop
div_end
        MOV R0, R5
        MOV R1, R7
        POP{R4-R7, LR}
        BX LR

IsDivisible
        PUSH{LR}
        MOV R2, R0
id_loop
        SUBS R2, R2, R1
        BPL id_loop
        ADDS R2, R2, R1
        MOV R0, #0
        CMP R2, #0
        MOVEQ R0, #1
        POP{LR}
        BX LR

        END