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|
;--------------------------------------------------------------------------
; mulchar.s
;
; Copyright (C) 2017, Philipp Klaus Krause
;
; 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.
;--------------------------------------------------------------------------
.hd64
.area _CODE
; 16 x 16 -> 16 multiplication.
.globl __mulint
__mulint:
pop af
pop bc
pop de
push de
push bc
push af
;; 16-bit multiplication
;;
;; Entry conditions
;; bc = multiplicand
;; de = multiplier
;;
;; Exit conditions
;; hl = less significant word of product
;;
;; Register used: AF,BC,DE,HL
__mul16::
; Swap lower bytes while also copying them into hl
ld l, c
ld h, e
ld e, l
ld c, h
mlt bc
mlt de
mlt hl
ld a, c
add a, e
add a, h
ld h, a
ret
|
