DrawCircle.asm

; r0 = base
; r1 = setPixel X
; r2 = setPixel Y
; r3 = r
; r4 = xm
; r5 = ym
; r6 = x
; r7 = y
; r8 = err
; r9 = temp calc register
; r11 = color
circle ; base, xm, ym, r, color
    stmfd sp!, {r0-r12, lr}
    mov r11, r4
    mov r4, r1
    mov r5, r2
    rsb r6, r3, #0
    mov r7, #0
    mov r8, #2
    sub r8, r8, r3, lsl #1
circleloop
    sub r1, r4, r6
    add r2, r5, r7
    bl setPixel
    sub r1, r4, r7
    sub r2, r5, r6
    bl setPixel
    add r1, r4, r6
    sub r2, r5, r7
    bl setPixel
    add r1, r4, r7
    add r2, r5, r6
    bl setPixel
    mov r3, r8
    cmp r3, r7
    addle r7, r7, #1
    movle r9, r7, lsl #1
    addle r9, r9, #1
    addle r8, r8, r9
    cmp r3, r6
    bgt dc
    cmp r8, r7
    ble ndc
dc
    add r6, r6, #1
    mov r9, r6, lsl #1
    add r9, r9, #1
    add r8, r8, r9
ndc
    cmp r6, #0
    blt circleloop
    ldmfd sp!, {r0-r12,pc}