https://github.com/akkartik/mu/blob/main/508circle.mu

     1 fn draw-circle screen: (addr screen), cx: int, cy: int, radius: int, color: int {
     2   var x: int
     3   var y: int
     4   var err: int
     5   # x = -r
     6   var tmp/eax: int <- copy radius
     7   tmp <- negate
     8   copy-to x, tmp
     9   # err = 2 - 2*r
    10   tmp <- copy radius
    11   tmp <- shift-left 1
    12   tmp <- negate
    13   tmp <- add 2
    14   copy-to err, tmp
    15   #
    16   var tmpx/ecx: int <- copy 0
    17   var tmpy/edx: int <- copy 0
    18   {
    19     # pixel(cx-x, cy+y)
    20     tmpx <- copy cx
    21     tmpx <- subtract x
    22     tmpy <- copy cy
    23     tmpy <- add y
    24     pixel screen, tmpx, tmpy, color
    25     # pixel(cx-y, cy-x)
    26     tmpx <- copy cx
    27     tmpx <- subtract y
    28     tmpy <- copy cy
    29     tmpy <- subtract x
    30     pixel screen, tmpx, tmpy, color
    31     # pixel(cx+x, cy-y)
    32     tmpx <- copy cx
    33     tmpx <- add x
    34     tmpy <- copy cy
    35     tmpy <- subtract y
    36     pixel screen, tmpx, tmpy, color
    37     # pixel(cx+y, cy+x)
    38     tmpx <- copy cx
    39     tmpx <- add y
    40     tmpy <- copy cy
    41     tmpy <- add x
    42     pixel screen, tmpx, tmpy, color
    43     # r = err
    44     tmp <- copy err
    45     copy-to radius, tmp
    46     # if (r <= y) { ++y; err += (y*2 + 1); }
    47     {
    48       tmpy <- copy y
    49       compare radius, tmpy
    50       break-if->
    51       increment y
    52       tmpy <- copy y
    53       tmpy <- shift-left 1
    54       tmpy <- increment
    55       add-to err, tmpy
    56     }
    57     # if (r > x || err > y) { ++x; err += (x*2 + 1); }
    58     $draw-circle:second-check: {
    59       {
    60         tmpx <- copy x
    61         compare radius, tmpx
    62         break-if->
    63         tmpy <- copy y
    64         compare err, tmpy
    65         break-if->
    66         break $draw-circle:second-check
    67       }
    68       increment x
    69       tmpx <- copy x
    70       tmpx <- shift-left 1
    71       tmpx <- increment
    72       add-to err, tmpx
    73     }
    74     # loop termination condition
    75     compare x, 0
    76     loop-if-<
    77   }
    78 }
    79
    80 fn draw-disc screen: (addr screen), cx: int, cy: int, radius: int, color: int, border-color: int {
    81   var r/eax: int <- copy 0
    82   {
    83     compare r, radius
    84     break-if->=
    85     draw-circle screen, cx cy, r, color
    86     r <- increment
    87     loop
    88   }
    89   draw-circle screen, cx cy, r, border-color
    90 }