bugfix in mandelbrot-fixed
Thanks to comparing regular ints with fixed-point ints, I was computing iterations for many screenfuls of pixels to the right of the current one. (Y-axis behaved similarly, but there it was just doing other work instead of busy-looping forever. If you don't have anything else to do, it doesn't matter what you do.)
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@ -112,20 +112,20 @@ fn mandelbrot screen: (addr screen) {
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var a/eax: int <- copy 0
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var b/ecx: int <- copy 0
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a, b <- screen-size screen
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var width-f/esi: int <- copy a
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width-f <- shift-left 0xb/log2-font-width-and-fixed-precision # 3 + 8 = 11
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var height-f/edi: int <- copy b
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height-f <- shift-left 0xc/log2-font-height-and-fixed-precision # 4 + 8 = 12
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var width/esi: int <- copy a
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width <- shift-left 3/log2-font-width
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var height/edi: int <- copy b
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height <- shift-left 4/log2-font-height
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var y/ecx: int <- copy 0
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{
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compare y, height-f
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compare y, height
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break-if->=
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var imaginary-f/ebx: int <- viewport-to-imaginary-f y, width-f, height-f
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var imaginary-f/ebx: int <- viewport-to-imaginary-f y, width, height
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var x/eax: int <- copy 0
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{
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compare x, width-f
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compare x, width
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break-if->=
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var real-f/edx: int <- viewport-to-real-f x, width-f
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var real-f/edx: int <- viewport-to-real-f x, width
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var iterations/esi: int <- mandelbrot-iterations-for-point real-f, imaginary-f, 0x400/max
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compare iterations, 0x400/max
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{
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@ -202,10 +202,12 @@ fn mandelbrot-y x-f: int, y-f: int, imaginary-f: int -> _/ebx: int {
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# ranges from -2 to +2. Viewport height just follows the viewport's aspect
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# ratio.
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fn viewport-to-real-f x: int, width-f: int -> _/edx: int {
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fn viewport-to-real-f x: int, width: int -> _/edx: int {
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# (x - width/2)*4/width
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var result-f/eax: int <- int-to-fixed x
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var half-width-f/ecx: int <- copy width-f
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var width-f/ecx: int <- copy width
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width-f <- shift-left 8/fixed-precision
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var half-width-f/edx: int <- copy width-f
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half-width-f <- shift-right-signed 1/log2
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result-f <- subtract half-width-f
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result-f <- shift-left 2/log4
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@ -213,12 +215,16 @@ fn viewport-to-real-f x: int, width-f: int -> _/edx: int {
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return result-f
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}
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fn viewport-to-imaginary-f y: int, width-f: int, height-f: int -> _/ebx: int {
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fn viewport-to-imaginary-f y: int, width: int, height: int -> _/ebx: int {
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# (y - height/2)*4/width
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var result-f/eax: int <- int-to-fixed y
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shift-right-signed height-f, 1/log2
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result-f <- subtract height-f
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var half-height-f/ecx: int <- copy height
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half-height-f <- shift-left 8/fixed-precision
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half-height-f <- shift-right-signed 1/log2
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result-f <- subtract half-height-f
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result-f <- shift-left 2/log4
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var width-f/ecx: int <- copy width
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width-f <- shift-left 8/fixed-precision
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result-f <- divide-fixed result-f, width-f
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return result-f
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}
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