sdcc/device/lib/mos6502/_mulschar.s

   1 ;-------------------------------------------------------------------------
   2 ;   _mulschar.s - routine for multiplication of 8 bit signed char
   3 ;
   4 ;   Copyright (C) 2009, Ullrich von Bassewitz
   5 ;   Copyright (C) 2022-2023, Gabriele Gorla
   6 ;
   7 ;   This library is free software; you can redistribute it and/or modify it
   8 ;   under the terms of the GNU General Public License as published by the
   9 ;   Free Software Foundation; either version 2, or (at your option) any
  10 ;   later version.
  11 ;
  12 ;   This library is distributed in the hope that it will be useful,
  13 ;   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 ;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 ;   GNU General Public License for more details.
  16 ;
  17 ;   You should have received a copy of the GNU General Public License
  18 ;   along with this library; see the file COPYING. If not, write to the
  19 ;   Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  20 ;   MA 02110-1301, USA.
  21 ;
  22 ;   As a special exception, if you link this library with other files,
  23 ;   some of which are compiled with SDCC, to produce an executable,
  24 ;   this library does not by itself cause the resulting executable to
  25 ;   be covered by the GNU General Public License. This exception does
  26 ;   not however invalidate any other reasons why the executable file
  27 ;   might be covered by the GNU General Public License.
  28 ;-------------------------------------------------------------------------
  29
  30         .module _mulschar
  31
  32 ;--------------------------------------------------------
  33 ; exported symbols
  34 ;--------------------------------------------------------
  35         .globl __mulschar
  36         .globl __muluschar
  37         .globl __mulsuchar
  38
  39 ;--------------------------------------------------------
  40 ; overlayable function parameters in zero page
  41 ;--------------------------------------------------------
  42         .area   OSEG    (PAG, OVR)
  43
  44 ;--------------------------------------------------------
  45 ; local aliases
  46 ;--------------------------------------------------------
  47         .define arg1 "___SDCC_m6502_ret0"
  48         .define arg2 "___SDCC_m6502_ret2"
  49         .define s1 "___SDCC_m6502_ret4"
  50         .define s2 "___SDCC_m6502_ret5"
  51
  52 ;--------------------------------------------------------
  53 ; code
  54 ;--------------------------------------------------------
  55         .area CODE
  56
  57 __mulschar:
  58         sta     *s1
  59         cmp     #0x00
  60         bpl     pos1
  61         sec
  62         eor     #0xff
  63         adc     #0x00
  64 pos1:
  65         sta     *arg1
  66         txa
  67         sta     *s2
  68         bpl     pos2
  69         sec
  70         eor     #0xff
  71         adc     #0x00
  72 pos2:
  73         sta     *arg2
  74
  75         jsr     ___umul8
  76         lda     *s1
  77         eor     *s2
  78         bpl     skip
  79         lda     arg2
  80         jmp     ___negax
  81
  82 skip:   lda     arg2
  83         rts
  84
  85 __muluschar:
  86         stx     *__mulint_PARM_2
  87         ldx     #0x00
  88         stx     *__mulint_PARM_2+1
  89         cmp     #0x00
  90         bpl     pos1m
  91         ldx     #0xff
  92 pos1m:
  93         jmp     __mulint
  94
  95 __mulsuchar:
  96         sta     *__mulint_PARM_2
  97         txa
  98         ldx     #0x00
  99         stx     *__mulint_PARM_2+1
 100         cmp     #0x00
 101         bpl     pos2m
 102         ldx     #0xff
 103 pos2m:
 104         jmp     __mulint