Difference between revisions of "Programming:Integer Division"
From CPCWiki - THE Amstrad CPC encyclopedia!
m (→Fast 32bit division) |
m (→32bit division) |
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'''Destroyed:''' AF,DE,IY | '''Destroyed:''' AF,DE,IY | ||
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+ | '''CPC Cycles:''' approximately 7800, 1900 usec | ||
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+ | '''Size:''' 91 bytes | ||
<pre> | <pre> | ||
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ret ;IY,BC=Value1 DIV Value2 | ret ;IY,BC=Value1 DIV Value2 | ||
</pre> | </pre> | ||
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== Fast 32bit division == | == Fast 32bit division == |
Revision as of 12:51, 16 November 2015
Contents
8bit division
Input: HL=Value1, C=Value2
Output: L=Value1/Value2, H=Value1 MOD Value2
Destroyed: AF,BC
LD B,8 Div_Next: ADD HL,HL LD A,H SUB C JR C,Div_NXTB LD H,A INC L Div_NXTB: DJNZ Div_Next RET
16bit division
Input: BC=Value1, DE=Value2
Output: HL=Value1/Value2, DE=Value1 MOD Value2
Destroyed: AF,BC
clcd16 ld a,e or d ld hl,0 ret z ld a,b ld b,16 clcd161 rl c rla adc hl,hl sbc hl,de jr nc,clcd162 add hl,de clcd162 ccf djnz clcd161 ex de,hl rl c rla ld h,a ld l,c ret
24bit division
Input: A,BC=Value1, DE=Value2
Output: HL=Value1/Value2, DE=Value1 MOD Value2
Destroyed: AF,BC,IX,IYL
clcdiv db #dd:ld l,e db #dd:ld h,d ;IX=Value2 ld e,a ;E,BC=Value1(Counter) ld hl,0 db #dd:ld a,l db #dd:or h ret z ld d,l ;D,HL=CalcVar db #fd:ld l,24 ;IYL=Counter clcdiv1 rl c rl b rl e rl l rl h rl d ld a,l db #dd:sub l ld l,a ld a,h db #dd:sbc h ld h,a ld a,d sbc 0 ld d,a ;D,HL=D,HL-IX jr nc,clcdiv2 ld a,l db #dd:add l ld l,a ld a,h db #dd:adc h ld h,a ld a,d adc 0 ld d,a scf clcdiv2 ccf db #fd:dec l jr nz,clcdiv1 ex de,hl ;DE=Value1 MOD Value2 rl c rl b ld l,c ld h,b ;HL=Value1 DIV Value2 ret
32bit division
Input: IY,BC=Value1, IX=Value2
Output: IY,BC=Value1/Value2, HL=Value1 MOD Value2
Destroyed: AF,DE,IY
CPC Cycles: approximately 7800, 1900 usec
Size: 91 bytes
clcd32c db 0 clcd32 ld hl,0 db #dd:ld a,l db #dd:or h ret z ;IY,BC=Value1(Counter) ld de,0 ;DE,HL=CalcVar ld a,32 ;Set Counter to 32 clcd321 ld (clcd32c),a rl c rl b db #fd:ld a,l:rla:db #fd:ld l,a db #fd:ld a,h:rla:db #fd:ld h,a rl l rl h rl e rl d ld a,l db #dd:sub l ld l,a ld a,h db #dd:sbc h ld h,a ld a,e sbc 0 ld e,a ld a,d sbc 0 ld d,a jr nc,clcd322 ld a,l db #dd:add l ld l,a ld a,h db #dd:adc h ld h,a ld a,e adc 0 ld e,a ld a,d adc 0 ld d,a scf clcd322 ccf ld a,(clcd32c) dec a jr nz,clcd321 ;HL=Value1 MOD Value2 rl c rl b db #fd:ld a,l:rla:db #fd:ld l,a db #fd:ld a,h:rla:db #fd:ld h,a ret ;IY,BC=Value1 DIV Value2
Fast 32bit division
Input: HL,DE=Value1, BC=Value2
Output: BCDE=Value1/Value2, HL=Value1 MOD Value2
Destroyed: AF
Not used: IX, IY
CPC Cycles: 1080-2572 (1826 on average), 270-643 usec (456 on average)
Size: 261 bytes
div_r macro local t2 EX DE, HL ADD HL, HL EX DE, HL ADC HL, HL LD A, L ADD A, C LD A, H ADC A, B JR NC, t2 ADD HL, BC INC DE t2 endm div_e macro local t1,t2 EX DE, HL ADD HL, HL EX DE, HL ADC HL, HL JR C, t1 LD A, L ADD A, C LD A, H ADC A, B JR NC, t2 t1 ADD HL, BC INC DE t2 endm div32x16 proc ; BCDE = HLDE/BC, HL = HLDE%BC local DIV16, DIV32R, DIV32E DEC BC LD A, B CPL LD B, A LD A, C CPL LD C, A ADD A, L LD A, B ADC A, H JR NC, DIV16 PUSH DE EX DE, HL LD HL, 0000 CALL DIV32R EX DE, HL EX (SP), HL EX DE, HL CALL DIV32E POP BC RET DIV16 CALL DIV32E LD BC, 0000 RET DIV32R ; DE = HLDE/(-BC), HL = HLDE%(-BC), -BC < $8000 CALL $+3 rept 8 div_r endm RET DIV32E ; DE = HLDE/(-BC), HL = HLDE%(-BC) CALL $+3 rept 8 div_e endm RET endp