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;--------------------------------------------------------------------------
; mulchar.s
;
; Copyright (C) 2000, Michael Hope
;
; This library is free software; you can redistribute it and/or modify it
; under the terms of the GNU General Public License as published by the
; Free Software Foundation; either version 2, or (at your option) any
; later version.
;
; This library is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this library; see the file COPYING. If not, write to the
; Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
; MA 02110-1301, USA.
;
; As a special exception, if you link this library with other files,
; some of which are compiled with SDCC, to produce an executable,
; this library does not by itself cause the resulting executable to
; be covered by the GNU General Public License. This exception does
; not however invalidate any other reasons why the executable file
; might be covered by the GNU General Public License.
;--------------------------------------------------------------------------
.area _CODE
.globl __mulint
__mulint:
ld bc, 2 (sp)
ld de, 4 (sp)
;; 16-bit multiplication
;;
;; Entry conditions
;; bc = multiplicand
;; de = multiplier
;;
;; Exit conditions
;; hl = less significant word of product
;;
;; Register used: AF,BC,DE,HL
__mul16::
xor a,a
ld l,a
or a,b
ld b,#16
;; Optimise for the case when this side has 8 bits of data or
;; less. This is often the case with support address calls.
jr NZ,2$
ld b,#8
ld a,c
1$:
;; Taken from z88dk, which originally borrowed from the
;; Spectrum rom.
add hl,hl
2$:
rl c
rla ;DLE 27/11/98
jr NC,3$
add hl,de
3$:
djnz 1$
ret
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