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subdi3.S revision 1.1 
      1  1.1  mrg ;   Copyright (C) 2017-2018 Free Software Foundation, Inc.
      2  1.1  mrg ;   Contributed by Sebastian Perta.
      3  1.1  mrg ;
      4  1.1  mrg ; This file is free software; you can redistribute it and/or modify it
      5  1.1  mrg ; under the terms of the GNU General Public License as published by the
      6  1.1  mrg ; Free Software Foundation; either version 3, or (at your option) any
      7  1.1  mrg ; later version.
      8  1.1  mrg ;
      9  1.1  mrg ; This file is distributed in the hope that it will be useful, but
     10  1.1  mrg ; WITHOUT ANY WARRANTY; without even the implied warranty of
     11  1.1  mrg ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     12  1.1  mrg ; General Public License for more details.
     13  1.1  mrg ;
     14  1.1  mrg ; Under Section 7 of GPL version 3, you are granted additional
     15  1.1  mrg ; permissions described in the GCC Runtime Library Exception, version
     16  1.1  mrg ; 3.1, as published by the Free Software Foundation.
     17  1.1  mrg ;
     18  1.1  mrg ; You should have received a copy of the GNU General Public License and
     19  1.1  mrg ; a copy of the GCC Runtime Library Exception along with this program;
     20  1.1  mrg ; see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
     21  1.1  mrg ; <http://www.gnu.org/licenses/>.
     22  1.1  mrg 
     23  1.1  mrg 
     24  1.1  mrg #include "vregs.h"
     25  1.1  mrg 
     26  1.1  mrg     .text
     27  1.1  mrg 
     28  1.1  mrg START_FUNC ___subdi3
     29  1.1  mrg 
     30  1.1  mrg     movw  hl, sp       ; use HL-based addressing (allows for direct subw)
     31  1.1  mrg 
     32  1.1  mrg     movw  ax, [hl+4]
     33  1.1  mrg     subw  ax, [hl+12]
     34  1.1  mrg     movw  r8, ax
     35  1.1  mrg 
     36  1.1  mrg     mov   a, [hl+6]    ; middle bytes of the result are determined using 8-bit
     37  1.1  mrg     subc  a, [hl+14]   ; SUBC insns which both account for and update the carry bit
     38  1.1  mrg     mov   r10, a       ; (no SUBWC instruction is available)
     39  1.1  mrg     mov   a, [hl+7]
     40  1.1  mrg     subc  a, [hl+15]
     41  1.1  mrg     mov   r11, a
     42  1.1  mrg 
     43  1.1  mrg     mov   a, [hl+8]
     44  1.1  mrg     subc  a, [hl+16]
     45  1.1  mrg     mov   r12, a
     46  1.1  mrg     mov   a, [hl+9]
     47  1.1  mrg     subc  a, [hl+17]
     48  1.1  mrg     mov   r13, a
     49  1.1  mrg 
     50  1.1  mrg     movw  ax, [hl+10]
     51  1.1  mrg     sknc               ; account for the possible carry from the
     52  1.1  mrg     decw  ax           ; latest 8-bit operation
     53  1.1  mrg     subw  ax, [hl+18]
     54  1.1  mrg     movw  r14, ax
     55  1.1  mrg 
     56  1.1  mrg     ret
     57  1.1  mrg 
     58  1.1  mrg END_FUNC ___subdi3
     59