Z80 Routines:Math:Multiplication - Revision history

Zeda: `sbc hl,bc` ==> `sbc hl,de`

2022-04-29T02:31:00Z

`sbc hl,bc` ==> `sbc hl,de`

2022-04-29T00:06:34Z

Fix bug when BC is negative (thanks, Sue Doenim!)

2019-09-30T22:28:00Z

optimized the mult_h_e routine

2019-08-02T11:41:44Z

‎Signed versions

2011-12-09T01:10:31Z

2011-12-09T00:54:39Z

2010-07-03T19:33:21Z

‎16*16 multiplication

2010-07-03T19:33:05Z

‎16*16 multiplication: It is actually less T states and the same size to do ld hl,0 than ld h,0 / ld l,h

2009-11-09T08:47:37Z

2009-11-05T16:49:35Z

added categorization

@@ Line 129: / Line 129: @@
    or b
    jp p,mulbpos
-   sbc hl,bc
+   sbc hl,de
 mulbpos:

@@ Line 101: / Line 101: @@
 The following routine multiplies bc by de and places the signed result in dehl.
 ; call with bc, de = 16 bit signed numbers to multiply
@@ Line 115: / Line 121: @@
    ld h,a
    ld l,a
    bit 7,d
    jr z,muldpos
    sbc hl,bc
 muldpos:
-   ld a,b
-   sra a
+   or b
-   and 0C0h
+   jp p,mulbpos
-  add a,d
+   sbc hl,bc
-  ld d,a
+mulbpos:
    ld a,16
@@ Line 138: / Line 145: @@
    jr nz,mulloop
 </nowiki>

@@ Line 15: / Line 15: @@
   <nowiki>
 mult_h_e
-    ld	l, 0
+    ld	d, 0	; Combining the overhead and
-   ld	d, l
+    sla	h	; optimised first iteration
+    sbc	a, a
-    sla	h		; optimised 1st iteration
+   and	e
-    jr	nc, $+3
+    ld	l, a
-    ld	l, e
-    ld b, 7
+    ld	b, 7
 _loop:
     add	hl, hl

← Older revision		Revision as of 11:41, 2 August 2019
Line 98:		Line 98:

	=== 16*8 multiplication ===		=== 16*8 multiplication ===
		+
		+	=== 16*16 multiplication ===
		+
		+	The following routine multiplies bc by de and places the signed result in dehl.
		+
		+	<nowiki>; 16 bit signed multiply by John Metcalf
		+	; 32 bytes, average approx ~1090 cycles
		+
		+	; call with bc, de = 16 bit signed numbers to multiply
		+	; returns de:hl = 32 bit signed product
		+	; corrupts a
		+
		+	; de:hl = bc*de
		+
		+	multiply:
		+	xor a
		+	ld h,a
		+	ld l,a
		+	bit 7,d
		+	jr z,muldpos
		+	sbc hl,bc
		+	muldpos:
		+	ld a,b
		+	sra a
		+	and 0C0h
		+	add a,d
		+	ld d,a
		+
		+	ld a,16
		+	mulloop:
		+	add hl,hl
		+	rl e
		+	rl d
		+	jr nc,mul0bit
		+	add hl,bc
		+	jr nc,mul0bit
		+	inc de
		+	mul0bit:
		+	dec a
		+	jr nz,mulloop
		+	</nowiki>

← Older revision		Revision as of 01:10, 9 December 2011
Line 89:		Line 89:

	ret		ret
−	~~</nowiki>~~
−
−	~~=== 24*24 multiplication ===~~
−
−	~~The following routine multiplies bcd by ehl and places the result in bcdehl. It uses 2 bytes of ram, but those can be substituted for IX half registers. (By thepenguin77)~~
−
−	~~<nowiki>~~
−	~~multDBCbyEHL:~~
−
−	~~push de~~
−	~~push hl~~
−
−	~~ld ix, $8000~~
−	~~ld (ix), l~~
−	~~xor a~~
−	~~ld h, a~~
−	~~ld l, a~~
−
−	~~call do8Bits~~
−
−	~~ld (ix+1), a~~
−	~~pop af~~
−	~~ld (ix), a~~
−	~~push de~~
−	~~ld a, (ix+1)~~
−
−	~~call do8Bits~~
−
−	~~ld (ix+1), a~~
−	~~pop af ;least sig number~~
−	~~ex de, hl~~
−	~~ex (sp), hl ;D and 2nd least sig in for new number~~
−	~~ld (ix), l~~
−	~~pop hl ;D and 2nd least sig~~
−	~~push af ;least sig number~~
−	~~push hl ;2nd least sig number~~
−	~~ex de, hl~~
−	~~ld a, (ix+1)~~
−
−	~~call do8Bits~~
−
−	~~ld b, a~~
−	~~ld c, h~~
−	~~ld d, l~~
−	~~pop hl~~
−	~~ld a, l~~
−	~~pop hl~~
−	~~ld h, a~~
−	~~ret~~
−
−	~~;####~~
−	~~;input: DBC = 1 number~~
−	~~; AHL = running number~~
−	~~; (ix) = to multiply by~~
−	~~;output: AHLE = output~~
−	~~; E is done~~
−	~~; DBC = 1 number~~
−
−	~~do8Bits:~~
−	~~ld (ix+1), 8~~
−	~~loop:~~
−	~~srl (ix)~~
−	~~jr nc, skip~~
−
−	~~add hl, bc~~
−	~~adc a, d~~
−	~~skip:~~
−	~~rra~~
−	~~rr h~~
−	~~rr l~~
−	~~rr e~~
−	~~dec (ix+1)~~
−	~~jr nz, loop~~
−	~~ret~~
	</nowiki>		</nowiki>

← Older revision		Revision as of 00:54, 9 December 2011
Line 89:		Line 89:

	ret		ret
		+	</nowiki>
		+
		+	=== 24*24 multiplication ===
		+
		+	The following routine multiplies bcd by ehl and places the result in bcdehl. It uses 2 bytes of ram, but those can be substituted for IX half registers. (By thepenguin77)
		+
		+	<nowiki>
		+	multDBCbyEHL:
		+
		+	push de
		+	push hl
		+
		+	ld ix, $8000
		+	ld (ix), l
		+	xor a
		+	ld h, a
		+	ld l, a
		+
		+	call do8Bits
		+
		+	ld (ix+1), a
		+	pop af
		+	ld (ix), a
		+	push de
		+	ld a, (ix+1)
		+
		+	call do8Bits
		+
		+	ld (ix+1), a
		+	pop af ;least sig number
		+	ex de, hl
		+	ex (sp), hl ;D and 2nd least sig in for new number
		+	ld (ix), l
		+	pop hl ;D and 2nd least sig
		+	push af ;least sig number
		+	push hl ;2nd least sig number
		+	ex de, hl
		+	ld a, (ix+1)
		+
		+	call do8Bits
		+
		+	ld b, a
		+	ld c, h
		+	ld d, l
		+	pop hl
		+	ld a, l
		+	pop hl
		+	ld h, a
		+	ret
		+
		+	;####
		+	;input: DBC = 1 number
		+	; AHL = running number
		+	; (ix) = to multiply by
		+	;output: AHLE = output
		+	; E is done
		+	; DBC = 1 number
		+
		+	do8Bits:
		+	ld (ix+1), 8
		+	loop:
		+	srl (ix)
		+	jr nc, skip
		+
		+	add hl, bc
		+	adc a, d
		+	skip:
		+	rra
		+	rr h
		+	rr l
		+	rr e
		+	dec (ix+1)
		+	jr nz, loop
		+	ret
	</nowiki>		</nowiki>

@@ Line 67: / Line 67: @@
   <nowiki>
 mult_de_bc
-    ld	hl,0
+    ld	hl, 0
     sla	e		; optimised 1st iteration

@@ Line 7: / Line 7: @@
 They can easily be unrolled to gain some speed.
-== 8*8 multiplication ==
+== Unsigned versions ==
 The following routine multiplies h by e and places the result in hl
@@ Line 31: / Line 33: @@
   </nowiki>
-== 16*8 multiplication ==
+=== 16*8 multiplication ===
 The following routine multiplies de by a and places the result in ahl (which means a is the most significant byte of the product, l the least significant and h the intermediate one...)
@@ Line 59: / Line 61: @@
   </nowiki>
-== 16*16 multiplication ==
+=== 16*16 multiplication ===
 The following routine multiplies bc by de and places the result in dehl.
@@ Line 89: / Line 91: @@
     ret
   </nowiki>

← Older revision		Revision as of 16:49, 5 November 2009
Line 1:		Line 1:
		+	[[Category:Z80 Routines:Math\|Multiplication]]
		+	[[Category:Z80 Routines\|Multiplication]]
		+
	== Introduction ==		== Introduction ==