sdcc/device/lib/mos6502/_divuint.s

   1 ;-------------------------------------------------------------------------
   2 ;   _divuint.s - routine for division of 16 bit unsigned int
   3 ;
   4 ;   Copyright (C) 1998, Ullrich von Bassewitz
   5 ;   Copyright (C) 2022, 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 _divuint
  31
  32 ;--------------------------------------------------------
  33 ; exported symbols
  34 ;--------------------------------------------------------
  35         .globl __divuint_PARM_2
  36         .globl __divsint_PARM_2
  37         .globl __moduint_PARM_2
  38         .globl __modsint_PARM_2
  39         .globl __divuint
  40         .globl ___udivmod16
  41
  42 ;--------------------------------------------------------
  43 ; overlayable function parameters in zero page
  44 ;--------------------------------------------------------
  45         .area   OSEG    (PAG, OVR)
  46 __divuint_PARM_2:
  47 __divsint_PARM_2:
  48 __moduint_PARM_2:
  49 __modsint_PARM_2:
  50         .ds 2
  51
  52 ;--------------------------------------------------------
  53 ; local aliases
  54 ;--------------------------------------------------------
  55         .define res "___SDCC_m6502_ret0"
  56         .define den "__divuint_PARM_2"
  57         .define rem "___SDCC_m6502_ret2"
  58         .define s1  "___SDCC_m6502_ret4"
  59         .define s2  "___SDCC_m6502_ret5"
  60
  61 ;--------------------------------------------------------
  62 ; code
  63 ;--------------------------------------------------------
  64         .area CODE
  65
  66 __divuint:
  67         jsr     ___udivmod16
  68         lda     *res+0
  69         ldx     *res+1
  70         rts
  71
  72 ___udivmod16:
  73         sta     *res+0
  74         stx     *res+1
  75
  76         lda     #0
  77         sta     *rem+1
  78         ldy     #16
  79 ;       ldx     __divuint_PARM_2+1
  80 ;       beq     div16x8
  81 next_bit:
  82         asl     *res+0
  83         rol     *res+1
  84         rol     a
  85         rol     *rem+1
  86
  87         tax
  88         cmp     *den+0
  89         lda     *rem+1
  90         sbc     *den+1
  91         bcc     L1
  92         sta     *rem+1
  93         txa
  94         sbc     *den+0
  95         tax
  96         inc     *res+0
  97 L1:
  98         txa
  99         dey
 100         bne     next_bit
 101         sta     *rem+0
 102         rts
 103
 104 ;div16x8:
 105 ;LL0:
 106 ;       asl     *___SDCC_m6502_ret0+0
 107 ;       rol     *___SDCC_m6502_ret0+1
 108 ;       rol     a
 109 ;       bcs     LL1
 110 ;       cmp     __divuint_PARM_2+0
 111 ;       bcc     LL2
 112 ;LL1:
 113 ;       sbc     __divuint_PARM_2+0
 114 ;       inc     *___SDCC_m6502_ret0+0
 115 ;LL2:
 116 ;       dey
 117 ;       bne     LL0
 118 ;       sta     *___SDCC_m6502_ret2+0
 119 ;
 120 ;       lda     *___SDCC_m6502_ret0+0
 121 ;       ldx     *___SDCC_m6502_ret0+1
 122 ;       rts
 123