mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-11-08 16:07:14 +00:00
352 lines
6.7 KiB
ArmAsm
352 lines
6.7 KiB
ArmAsm
; Fast mutiply
|
|
|
|
|
|
; Note for our purposes we only care about 8.8 x 8.8 fixed point
|
|
; with 8.8 result, which means we only care about the middle two bytes
|
|
; of the 32 bit result. So we disable generation of the high and low byte
|
|
; to save some cycles.
|
|
|
|
;
|
|
; The old routine took around 700 cycles for a 16bitx16bit=32bit mutiply
|
|
; This routine, at an expense of 2kB of looku tables, takes around 250
|
|
; If you reuse a term the next time this drops closer to 200
|
|
|
|
; This routine was described by Stephen Judd and found
|
|
; in The Fridge and in the C=Hacking magazine
|
|
; http://codebase64.org/doku.php?id=base:seriously_fast_multiplication
|
|
|
|
; The key thing to note is that
|
|
; (a+b)^2 (a-b)^2
|
|
; a*b = ------- - --------
|
|
; 4 4
|
|
; So if you have tables of the squares of 0..511 you can lookup and subtract
|
|
; instead of multiplying.
|
|
|
|
; Table generation: I:0..511
|
|
; square1_lo = <((I*I)/4)
|
|
; square1_hi = >((I*I)/4)
|
|
; square2_lo = <(((I-255)*(I-255))/4)
|
|
; square2_hi = >(((I-255)*(I-255))/4)
|
|
|
|
; Note: DOS3.3 starts at $9600
|
|
|
|
.ifndef square1_lo
|
|
square1_lo EQU $8E00
|
|
square1_hi EQU $9000
|
|
square2_lo EQU $9200
|
|
square2_hi EQU $9400
|
|
.endif
|
|
|
|
; for(i=0;i<512;i++) {
|
|
; square1_lo[i]=((i*i)/4)&0xff;
|
|
; square1_hi[i]=(((i*i)/4)>>8)&0xff;
|
|
; square2_lo[i]=( ((i-255)*(i-255))/4)&0xff;
|
|
; square2_hi[i]=(( ((i-255)*(i-255))/4)>>8)&0xff;
|
|
; }
|
|
|
|
init_multiply_tables:
|
|
|
|
; Build the add tables
|
|
|
|
ldx #$00
|
|
txa
|
|
.byte $c9 ; CMP #immediate - skip TYA and clear carry flag
|
|
lb1: tya
|
|
adc #$00 ; 0
|
|
ml1: sta square1_hi,x ; square1_hi[0]=0
|
|
tay ; y=0
|
|
cmp #$40 ; subtract 64 and update flags (c=0)
|
|
txa ; a=0
|
|
ror ; rotate
|
|
ml9: adc #$00 ; add 0
|
|
sta ml9+1 ; update add value
|
|
inx ; x=1
|
|
ml0: sta square1_lo,x ; square1_lo[0]=1
|
|
bne lb1 ; if not zero, loop
|
|
inc ml0+2 ; increment values
|
|
inc ml1+2 ; increment values
|
|
clc ; c=0
|
|
iny ; y=1
|
|
bne lb1 ; loop
|
|
|
|
; Build the subtract tables based on the existing one
|
|
|
|
ldx #$00
|
|
ldy #$ff
|
|
second_table:
|
|
lda square1_hi+1,x
|
|
sta square2_hi+$100,x
|
|
lda square1_hi,x
|
|
sta square2_hi,y
|
|
lda square1_lo+1,x
|
|
sta square2_lo+$100,x
|
|
lda square1_lo,x
|
|
sta square2_lo,y
|
|
dey
|
|
inx
|
|
bne second_table
|
|
|
|
|
|
rts
|
|
|
|
|
|
; Fast 16x16 bit unsigned multiplication, 32-bit result
|
|
; Input: NUM1H:NUM1L * NUM2H:NUM2L
|
|
; Result: RESULT3:RESULT2:RESULT1:RESULT0
|
|
;
|
|
; Does self-modifying code to hard-code NUM1H:NUM1L into the code
|
|
; carry=0: re-use previous NUM1H:NUM1L
|
|
; carry=1: reload NUM1H:NUM1L (58 cycles slower)
|
|
;
|
|
; clobbered: RESULT, X, A, C
|
|
; Allocation setup: T1,T2 and RESULT preferably on Zero-page.
|
|
;
|
|
; NUM1H (x_i), NUM1L (x_f)
|
|
; NUM2H (y_i), NUM2L (y_f)
|
|
|
|
; NUM1L * NUM2L = AAaa
|
|
; NUM1L * NUM2H = BBbb
|
|
; NUM1H * NUM2L = CCcc
|
|
; NUM1H * NUM2H = DDdd
|
|
;
|
|
; AAaa
|
|
; BBbb
|
|
; CCcc
|
|
; + DDdd
|
|
; ----------
|
|
; RESULT
|
|
|
|
;fixed_16x16_mul_unsigned:
|
|
|
|
multiply:
|
|
|
|
bcc num1_same_as_last_time ; 2nt/3
|
|
|
|
;============================
|
|
; Set up self-modifying code
|
|
; this changes the code to be hard-coded to multiply by NUM1H:NUM1L
|
|
;============================
|
|
|
|
lda NUM1L ; load the low byte ; 3
|
|
sta sm1a+1 ; 3
|
|
sta sm3a+1 ; 3
|
|
sta sm5a+1 ; 3
|
|
sta sm7a+1 ; 3
|
|
eor #$ff ; invert the bits for subtracting ; 2
|
|
sta sm2a+1 ; 3
|
|
sta sm4a+1 ; 3
|
|
sta sm6a+1 ; 3
|
|
sta sm8a+1 ; 3
|
|
lda NUM1H ; load the high byte ; 3
|
|
sta sm1b+1 ; 3
|
|
sta sm3b+1 ; 3
|
|
sta sm5b+1 ; 3
|
|
; sta sm7b+1 ;
|
|
eor #$ff ; invert the bits for subtractin ; 2
|
|
sta sm2b+1 ; 3
|
|
sta sm4b+1 ; 3
|
|
sta sm6b+1 ; 3
|
|
; sta sm8b+1 ;
|
|
;===========
|
|
; 52
|
|
|
|
num1_same_as_last_time:
|
|
|
|
;==========================
|
|
; Perform NUM1L * NUM2L = AAaa
|
|
;==========================
|
|
|
|
ldx NUM2L ; (low le) ; 3
|
|
sec ; 2
|
|
sm1a:
|
|
lda square1_lo,x ; 4
|
|
sm2a:
|
|
sbc square2_lo,x ; 4
|
|
|
|
; a is _aa
|
|
|
|
; sta RESULT+0 ;
|
|
|
|
sm3a:
|
|
lda square1_hi,x ; 4
|
|
sm4a:
|
|
sbc square2_hi,x ; 4
|
|
; a is _AA
|
|
sta _AA+1 ; 3
|
|
;===========
|
|
; 24
|
|
|
|
; Perform NUM1H * NUM2L = CCcc
|
|
sec ; 2
|
|
sm1b:
|
|
lda square1_lo,x ; 4
|
|
sm2b:
|
|
sbc square2_lo,x ; 4
|
|
; a is _cc
|
|
sta _cc+1 ; 3
|
|
sm3b:
|
|
lda square1_hi,x ; 4
|
|
sm4b:
|
|
sbc square2_hi,x ; 4
|
|
; a is _CC
|
|
sta _CC+1 ; 3
|
|
;===========
|
|
; 24
|
|
|
|
;==========================
|
|
; Perform NUM1L * NUM2H = BBbb
|
|
;==========================
|
|
ldx NUM2H ; 3
|
|
sec ; 2
|
|
sm5a:
|
|
lda square1_lo,x ; 4
|
|
sm6a:
|
|
sbc square2_lo,x ; 4
|
|
; a is _bb
|
|
sta _bb+1 ; 3
|
|
|
|
sm7a:
|
|
lda square1_hi,x ; 4
|
|
sm8a:
|
|
sbc square2_hi,x ; 4
|
|
; a is _BB
|
|
sta _BB+1 ; 3
|
|
;===========
|
|
; 27
|
|
|
|
;==========================
|
|
; Perform NUM1H * NUM2H = DDdd
|
|
;==========================
|
|
sec ; 2
|
|
sm5b:
|
|
lda square1_lo,x ; 4
|
|
sm6b:
|
|
sbc square2_lo,x ; 4
|
|
; a is _dd
|
|
sta _dd+1 ; 3
|
|
;sm7b:
|
|
; lda square1_hi,x ;
|
|
;sm8b:
|
|
; sbc square2_hi,x ;
|
|
; a = _DD
|
|
; sta RESULT+3 ;
|
|
;===========
|
|
; 13
|
|
|
|
;===========================================
|
|
; Add the separate multiplications together
|
|
;===========================================
|
|
|
|
clc ; 2
|
|
_AA:
|
|
lda #0 ; loading _AA ; 2
|
|
_bb:
|
|
adc #0 ; adding in _bb ; 2
|
|
sta RESULT+1 ; 3
|
|
;==========
|
|
; 9
|
|
; product[2]=_BB+_CC+c
|
|
|
|
_BB:
|
|
lda #0 ; loading _BB ; 2
|
|
_CC:
|
|
adc #0 ; adding in _CC ; 2
|
|
sta RESULT+2 ; 3
|
|
;===========
|
|
; 7
|
|
|
|
; product[3]=_DD+c
|
|
|
|
; bcc dd_no_carry1 ;
|
|
; inc RESULT+3 ;
|
|
clc ; 2
|
|
;=============
|
|
; 2
|
|
dd_no_carry1:
|
|
|
|
; product[1]=_AA+_bb+_cc
|
|
|
|
_cc:
|
|
lda #0 ; load _cc ; 2
|
|
adc RESULT+1 ; 3
|
|
sta RESULT+1 ; 3
|
|
|
|
; product[2]=_BB+_CC+_dd+c
|
|
|
|
_dd:
|
|
lda #0 ; load _dd ; 2
|
|
adc RESULT+2 ; 3
|
|
sta RESULT+2 ; 3
|
|
|
|
;===========
|
|
; 16
|
|
; product[3]=_DD+c
|
|
|
|
|
|
; bcc dd_no_carry2 ;
|
|
; inc RESULT+3 ;
|
|
|
|
;=============
|
|
; 0
|
|
|
|
dd_no_carry2:
|
|
|
|
; *z_i=product[1];
|
|
; *z_f=product[0];
|
|
|
|
; rts ; 6
|
|
|
|
|
|
;=================
|
|
; Signed multiply
|
|
;=================
|
|
|
|
;multiply:
|
|
|
|
; jsr fixed_16x16_mul_unsigned ; 6
|
|
|
|
lda NUM1H ; x_i ; 3
|
|
;===========
|
|
; 12
|
|
|
|
|
|
bpl x_positive ;^3/2nt
|
|
|
|
sec ; 2
|
|
lda RESULT+2 ; 3
|
|
sbc NUM2L ; 3
|
|
sta RESULT+2 ; 3
|
|
; lda RESULT+3 ;
|
|
; sbc NUM2H ;
|
|
; sta RESULT+3 ;
|
|
;============
|
|
; 10
|
|
|
|
x_positive:
|
|
|
|
lda NUM2H ; y_i ; 3
|
|
;============
|
|
; ; 6
|
|
|
|
bpl y_positive ;^3/2nt
|
|
|
|
|
|
sec ; 2
|
|
lda RESULT+2 ; 3
|
|
sbc NUM1L ; 3
|
|
sta RESULT+2 ; 3
|
|
; lda RESULT+3 ;
|
|
; sbc NUM1H ;
|
|
; sta RESULT+3 ;
|
|
;===========
|
|
; 10
|
|
|
|
y_positive:
|
|
ldx RESULT+2 ; *z_i=product[2]; ; 3
|
|
lda RESULT+1 ; *z_f=product[1]; ; 3
|
|
|
|
rts ; 6
|
|
;==========
|
|
; 12
|
|
|