WIP alternate imul16
not working at present
This commit is contained in:
parent
839330edb3
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1
.gitignore
vendored
1
.gitignore
vendored
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@ -1,3 +1,4 @@
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*.o
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*.xex
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tables.s
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.DS_Store
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8
Makefile
8
Makefile
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@ -2,13 +2,17 @@
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all : mandel.xex
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%.xex : %.o
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ld65 -C atari-asm-xex.cfg -o $@ $<
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mandel.xex : mandel.o tables.o
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ld65 -C ./atari-asm-xex.cfg -o $@ $+
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%.o : %.s
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ca65 -o $@ $<
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tables.s : tables.js
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node tables.js > tables.s
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clean :
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rm -f tables.s
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rm -f *.o
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rm -f *.xex
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120
mandel.s
120
mandel.s
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@ -22,11 +22,12 @@ total_ms = $a4 ; float48
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total_pixels = $aa ; float48
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temp = $b0 ; u16
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pixel_ptr = $b2 ; u16
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pixel_color = $b4 ; u8
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pixel_mask = $b5 ; u8
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pixel_shift = $b6 ; u8
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pixel_offset = $b7 ; u8
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temp2 = $b2 ; u16
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pixel_ptr = $b4 ; u16
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pixel_color = $b6 ; u8
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pixel_mask = $b7 ; u8
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pixel_shift = $b8 ; u8
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pixel_offset = $b9 ; u8
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; FP registers in zero page
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@ -83,6 +84,10 @@ SETVBV = $E45C
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mantissa .byte 6
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.endstruct
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.import mul_lobyte256
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.import mul_hibyte256
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.import mul_hibyte512
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.data
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strings:
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@ -206,6 +211,12 @@ color_map:
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add 4, dest, arg2, dest
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.endmacro
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.macro add_carry dest
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lda dest
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adc #0
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sta 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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@ -336,12 +347,12 @@ next:
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; 5 to 25 cycles
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.macro check_sign arg
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; Check sign bit and flip argument to postive,
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; keeping a count of sign bits in the X register.
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; keeping a count of sign bits in the Y register.
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.local positive
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lda arg + 1 ; 3 cyc
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bpl positive ; 2 cyc
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neg16 arg ; 18 cyc
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inx ; 2 cyc
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iny ; 2 cyc
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positive:
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.endmacro
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@ -370,13 +381,13 @@ positive:
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; min 470 cycles
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; max 780 cycles
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.proc imul16_func
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.proc imul16_func_orig
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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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ldx #0 ; 2 cyc
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; counts the number of sign bits in X
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ldy #0 ; 2 cyc
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; counts the number of sign bits in Y
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check_sign arg1 ; 5 to 25 cyc
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check_sign arg2 ; 5 to 25 cyc
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@ -396,7 +407,94 @@ positive:
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.endrepeat
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; In case of mixed input signs, return a negative result.
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cpx #1 ; 2 cyc
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cpy #1 ; 2 cyc
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bne positive_result ; 2 cyc
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neg32 result ; 34 cyc
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positive_result:
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rts ; 6 cyc
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.endproc
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; Adapted from https://everything2.com/title/Fast+6502+multiplication
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.macro imul8 dest, arg1, arg2
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.scope
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mul_factor_a = arg1
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mul_factor_x = arg2
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mul_product_lo = dest
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mul_product_hi = dest + 1
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lda mul_factor_a ; setup: 6 cycles
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;ldx mul_factor_x
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clc ; (a + x)^2/2: 23 cycles
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adc mul_factor_x
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tax
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bcc under256
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lda mul_hibyte512,x
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bcs next
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under256:
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lda mul_hibyte256,x
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sec
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next:
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sta mul_product_hi
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lda mul_lobyte256,x
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ldx mul_factor_a ; - a^2/2: 20 cycles
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sbc mul_lobyte256,x
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sta mul_product_lo
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lda mul_product_hi
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sbc mul_hibyte256,x
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sta mul_product_hi
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ldx mul_factor_x ; + x & a & 1: 22 cycles
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txa ; (this is a kludge to correct a
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and mul_factor_a ; roundoff error that makes odd * odd too low)
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and #1
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clc
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adc mul_product_lo
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bcc small_product
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inc mul_product_hi
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small_product:
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sec ; - x^2/2: 25 cycles
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sbc mul_lobyte256,x
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lda mul_product_hi
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sbc mul_hibyte256,x
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sta mul_product_hi
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.endscope
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.endmacro
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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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ldy #0 ; 2 cyc
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; counts the number of sign bits in Y
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check_sign arg1 ; 5 to 25 cyc
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check_sign arg2 ; 5 to 25 cyc
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lda #0
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sta result + 0
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sta result + 1
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sta result + 2
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sta result + 3
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imul8 temp, arg1, arg2
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add16 result, result, temp
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imul8 temp, arg1 + 1, arg2
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add16 result + 1, result + 1, temp
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imul8 temp, arg1, arg2 + 1
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add16 result + 1, result + 1, temp
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add_carry result + 3
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imul8 temp, arg1 + 1, arg2 + 1
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add16 result + 2, result + 2, temp
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; In case of mixed input signs, return a negative result.
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cpy #1 ; 2 cyc
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bne positive_result ; 2 cyc
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neg32 result ; 34 cyc
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positive_result:
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