sdcc/device/lib/sm83/abs.s

   1 ;--------------------------------------------------------------------------
   2 ;  abs.s
   3 ;
   4 ;  Copyright (C) 2020, Sergey Belyashov
   5 ;  Copyright (c) 2021, Philipp Klaus Krause
   6 ;  Copyright (c) 2022, Sebastian 'basxto' Riedel (sdcc@basxto.de)
   7 ;
   8 ;  This library is free software; you can redistribute it and/or modify it
   9 ;  under the terms of the GNU General Public License as published by the
  10 ;  Free Software Foundation; either version 2, or (at your option) any
  11 ;  later version.
  12 ;
  13 ;  This library is distributed in the hope that it will be useful,
  14 ;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 ;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16 ;  GNU General Public License for more details.
  17 ;
  18 ;  You should have received a copy of the GNU General Public License
  19 ;  along with this library; see the file COPYING. If not, write to the
  20 ;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  21 ;   MA 02110-1301, USA.
  22 ;
  23 ;  As a special exception, if you link this library with other files,
  24 ;  some of which are compiled with SDCC, to produce an executable,
  25 ;  this library does not by itself cause the resulting executable to
  26 ;  be covered by the GNU General Public License. This exception does
  27 ;  not however invalidate any other reasons why the executable file
  28 ;   might be covered by the GNU General Public License.
  29 ;--------------------------------------------------------------------------
  30
  31         .area   _CODE
  32
  33         .globl _abs
  34
  35 _abs::
  36         ld      c, e
  37         ld      b, d
  38         bit     7, b
  39         ret     Z ; Return since positive
  40         xor     a ; 0
  41         sub     e ; 0-e
  42         ld      c, a
  43         sbc     d ; 0-e-d
  44         add     e ; 0-d
  45         ld      b, a
  46         ret