arch/.unmaintained/m68k-emul/utility/umult32.s

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Utility 32 bit multiplication routines. m68k version.
   6     Lang: english
   7 */
   8
   9 #include "machine.i"
  10
  11 /* SMult32()/UMult32():
  12     These are the signed/unsigned 32 bit multiplication routines.
  13     I have two different possibilities here since I could be running
  14     on a system without the corresponding muls.l/mulu.l calls.
  15
  16     After some soul searching I am happy that these routines don't
  17     have to be separated between signed/unsigned since the sign is
  18     correct, or the number overflows.
  19
  20     The native versions do make the difference however.
  21
  22     What I do is SetFunction() the correct function in later.
  23 */
  24     .text
  25     .balign 16
  26
  27     .globl  AROS_SLIB_ENTRY(SMult32,Utility)
  28     .globl  AROS_SLIB_ENTRY(UMult32,Utility)
  29     .globl  AROS_SLIB_ENTRY(UMult32_020,Utility)
  30
  31     .type   AROS_SLIB_ENTRY(SMult32,Utility),@function
  32     .type   AROS_SLIB_ENTRY(UMult32,Utility),@function
  33     .type   AROS_SLIB_ENTRY(UMult32_020,Utility),@function
  34
  35 AROS_SLIB_ENTRY(UMult32_020,Utility):
  36     mulu.l  %d1,%d0
  37     rts
  38
  39 AROS_SLIB_ENTRY(SMult32,Utility):
  40 AROS_SLIB_ENTRY(UMult32,Utility):
  41 /*
  42     What do we have to do
  43     d0 = (a^16 + b), d1 = (c^16 = d)
  44     res = ac^32 + (ad + bc)^16 + bd
  45
  46     Now, ac^32 can be thrown away, as can the high 16 bits of ad + bd
  47 */
  48     movem.l  %d2/%d3,-(%sp)
  49     moveq.l #0,%d2
  50     moveq.l #0,%d3
  51
  52     /* ad */
  53     move.w  %d1,%d3
  54     swap    %d0
  55     mulu    %d0,%d3
  56
  57     /* bc */
  58     swap    %d0
  59     move.w  %d0,%d2
  60     swap    %d1
  61     mulu    %d1,%d2
  62
  63     /* (ad + bc)^16 */
  64     add.l   %d3,%d2
  65     swap    %d2
  66     clr.w   %d2
  67
  68     /* bd + (ad + bc)^16 */
  69     swap    %d1
  70     mulu    %d1,%d0
  71     add.l   %d2,%d0
  72     movem.l  (%sp)+,%d2/%d3
  73     rts
  74