flesh out the mandelbrot iteration loop
some bits i missed increased total to: 1939 - 3007 cycles per iteration probably still buggy, will test later :D
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mandel.s
207
mandel.s
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@ -1,14 +1,99 @@
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; Our zero-page vars
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sx = $80 ; 8 bits: screen pixel x
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sy = $81 ; 8 bits: screen pixel y
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cx = $82 ; 16 bits fixed point
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cy = $84 ; 16 bits fixed point
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zx = $86 ; 16 bits fixed point
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zy = $88 ; 16 bits fixed point
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zx_2 = $8a ; 32 bits fixed point
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zy_2 = $8e ; 32 bits fixed point
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zx_zy = $92 ; 32 bits fixed point
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dist = $96 ; 32 bits fixed point
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iter = $9a ; 8 bits iteration count
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temp = $a0 ; debug temp area
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; FP registers in zero page
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FR0 = $d4
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FRE = $da
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FR1 = $e0
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FR2 = $e6
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FRX = $ec
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.code
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.export start
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; 2 + 9 * byte cycles
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.macro add bytes, dest, arg1, arg2
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clc ; 2 cyc
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.repeat bytes, byte ; 9 * byte cycles
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lda arg1 + byte
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adc arg2 + byte
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sta dest + byte
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.endrepeat
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.endmacro
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.macro add16 dest, arg1, arg2
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add 2, dest, arg1, arg2
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.endmacro
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.macro add32 dest, arg1, arg2
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add 2, dest, arg2, dest
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.endmacro
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; 2 + 9 * byte cycles
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.macro sub bytes, dest, arg1, arg2
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sec ; 2 cyc
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.repeat bytes, byte ; 9 * byte cycles
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lda arg1 + byte
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sbc arg2 + byte
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sta dest + byte
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.endrepeat
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.endmacro
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.macro sub16 dest, arg1, arg2
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sub 2, dest, arg1, arg2
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.endmacro
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.macro sub32 dest, arg1, arg2
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sub 4, dest, arg1, arg2
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.endmacro
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.macro shl bytes, arg
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asl arg
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.repeat bytes-1
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rol arg
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.endrepeat
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.endmacro
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.macro shl16 arg
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shl 2, arg
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.endmacro
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.macro shl24 arg
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shl 3, arg
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.endmacro
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.macro shl32 arg
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shl 4, arg
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.endmacro
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; 6 * bytes cycles
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.macro copy bytes, dest, arg
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.repeat bytes, byte ; 6 * bytes cycles
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lda arg + byte ; 3 cyc
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sta dest + byte ; 3 cyc
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.endrepeat
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.endmacro
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.macro copy16 dest, arg
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copy 2, dest, arg
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.endmacro
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.macro copy32 dest, arg
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copy 4, dest, arg
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.endmacro
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; 2 + 8 * byte cycles
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.macro neg bytes, arg
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sec ; 2 cyc
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@ -92,9 +177,17 @@ next:
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positive:
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.endmacro
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; 518 - 828 cyc
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.macro imul16 dest, arg1, arg2
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copy16 FR0, arg1 ; 12 cyc
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copy16 FR1, arg2 ; 12 cyc
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jsr imul16_func ; 470-780
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copy32 dest, FR2 ; 24 cyc
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.endmacro
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; min 470 cycles
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; max 780 cycles
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.proc imul16
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.proc imul16_func
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arg1 = FR0 ; 16-bit arg (clobbered)
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arg2 = FR1 ; 16-bit arg (clobbered)
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result = FR2 ; 32-bit result
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@ -128,7 +221,7 @@ positive_result:
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rts ; 6 cyc
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.endproc
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.macro round16_incdec arg
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.macro round16 arg
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; Round top 16 bits of 32-bit fixed-point number in-place
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.local zero
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.local one
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@ -178,61 +271,113 @@ next:
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.proc iter
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; still working on the fixed-point
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; should we just use 16-bit adds?
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; does that require extra rounding?
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; is the integer precision right?
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.proc mandelbrot
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; input:
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; cx: position scaled to 4.12 fixed point - -8..+7.9
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; cy: position scaled to 4.12
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;
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; output:
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; iter: iteration count at escape or 0
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; (cx and cy should be pre-scaled to 4.12 fixed point - -8..+7.9)
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; zx = 0
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; zy = 0
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; zx_2 = 0
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; zy_2 = 0
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; zx_zy = 0
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; dist = 0
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; iter = 0
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lda #00
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ldx iter - zx
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initloop:
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sta zx,x
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dex
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bne initloop
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loop:
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; 1652 - 2651 cyc
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; 1939 - 3007 cyc
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; iters++ = 2 cyc
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; iter++ & max-iters break = 7 cyc
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inc iter ; 5 cyc
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bne keep_going ; 2 cyc
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rts
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keep_going:
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; 4.12: (-8 .. +7.9)
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; zx = zx_2 + zy_2 + cx = 3 * 20 = 60 cyc
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; zx = zx_2 - zy_2 + cx = 3 * 20 = 60 cyc
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sub16 zx, zx_2, zy_2
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add16 zx, zx, cx
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; zy = zx_zy + zx_zy + cy = 3 * 20 = 60 cyc
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sub16 zy, zx_zy, zx_zy
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add16 zy, zy, cy
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; 8.24: (-128 .. +127.9)
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; zx_2 = zx * zx = 470 - 780 cyc
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; zy_2 = zy * zy = 470 - 780 cyc
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; zx_zy = zx * zy = 470 - 780 cyc
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; dist = zx_2 + zy_2 = 38 cyc
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; if dist >= 4 break, else continue iterating = 7 cyc
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; zx_2 = zx * zx = 518 - 828 cyc
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imul16 zx_2, zx, zx
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; shift and round zx_2 to 4.12 = (20 + 5) - (20 + 28) = 25 - 48 cyc
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; shift and round zy_2 to 4.12 = (20 + 5) - (20 + 28) = 25 - 48 cyc
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; shift and round zx_zy to 4.12 = (20 + 5) - (20 + 28) = 25 - 48 cyc
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; zy_2 = zy * zy = 518 - 828 cyc
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imul16 zy_2, zy, zy
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; zx_zy = zx * zy = 518 - 828 cyc
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imul16 zx_zy, zx, zy
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; dist = zx_2 + zy_2 = 38 cyc
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add32 dist, zx_2, zy_2
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; if dist >= 4 break, else continue iterating = 7 cyc
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lda dist + 3 ; 3 cyc
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cmp #4 ; 2 cyc
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bmi still_in ; 2 cyc
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rts
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still_in:
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; shift and round zx_2 to 4.12 = (60 + 5) - (60 + 28) = 65 - 88 cyc
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.repeat 4 ; 60 cyc
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shl24 zx_2 ; 15 cyc
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.endrepeat
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round16 zx_2 ; 5-28 cycles
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; shift and round zy_2 to 4.12 = (20 + 5) - (20 + 28) = 65 - 88 cyc
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.repeat 4 ; 60 cyc
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shl24 zy_2 ; 15 cyc
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.endrepeat
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round16 zy_2 ; 5-28 cycles
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; shift and round zx_zy to 4.12 = (20 + 5) - (20 + 28) = 65 - 88 cyc
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.repeat 4 ; 60 cyc
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shl24 zx_zy ; 15 cyc
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.endrepeat
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round16 zx_zy ; 5-28 cycles
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; if may be in the lake, look for looping output with a small buffer
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; as an optimization vs running to max iters
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jmp loop ; 3 cycles
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.endproc
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.proc start
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looplong:
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; FR0 = 5
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; FR1 = -3
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lda #5
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sta FR0
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lda #0
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sta FR0 + 1
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lda #$fd
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sta FR1
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; cx = -0.5
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lda #$f7
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sta cx
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lda #$ff
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sta FR1 + 1
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sta cx + 1
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jsr imul16
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; cy = 1
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lda #$10
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sta cy
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lda #$00
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sta cy + 1
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jsr mandelbrot
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; should have 32-bit -15 in FR2
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; save the completed iter count for debugging
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lda iter
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sta temp
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loop:
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jmp loop
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; keep looping over so we can work in the debugger
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jmp looplong
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.endproc
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