sdcc/device/lib/mos6502/abs.s

   1 ;-------------------------------------------------------------------------
   2 ;   abs.s - standard C library function
   3 ;
   4 ;   Copyright (C) 2023, Gabriele Gorla
   5 ;
   6 ;   This library is free software; you can redistribute it and/or modify it
   7 ;   under the terms of the GNU General Public License as published by the
   8 ;   Free Software Foundation; either version 2, or (at your option) any
   9 ;   later version.
  10 ;
  11 ;   This library is distributed in the hope that it will be useful,
  12 ;   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 ;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 ;   GNU General Public License for more details.
  15 ;
  16 ;   You should have received a copy of the GNU General Public License
  17 ;   along with this library; see the file COPYING. If not, write to the
  18 ;   Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  19 ;   MA 02110-1301, USA.
  20 ;
  21 ;   As a special exception, if you link this library with other files,
  22 ;   some of which are compiled with SDCC, to produce an executable,
  23 ;   this library does not by itself cause the resulting executable to
  24 ;   be covered by the GNU General Public License. This exception does
  25 ;   not however invalidate any other reasons why the executable file
  26 ;   might be covered by the GNU General Public License.
  27 ;-------------------------------------------------------------------------
  28
  29         .module _abs
  30
  31 ;--------------------------------------------------------
  32 ; exported symbols
  33 ;--------------------------------------------------------
  34         .globl _abs
  35         .globl ___negax
  36
  37 ;--------------------------------------------------------
  38 ; code
  39 ;--------------------------------------------------------
  40
  41         .area CODE
  42 _abs:
  43         cpx #0x00
  44         bpl skip
  45 ___negax:
  46         sec
  47         eor #0xff
  48         adc #0x00
  49         pha
  50         txa
  51         eor #0xff
  52         adc #0x00
  53         tax
  54         pla
  55 skip:
  56         rts
  57