arch/.unmaintained/m68k-native/utility/smult64.s

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Utility 64 bit multiplication routines. m68k version.
   6     Lang: english
   7 */
   8
   9 #include "machine.i"
  10
  11 /* SMult64()/UMult64():
  12     These are the signed/unsigned 64 bit multiplication routines.
  13     There are two possibilities here because as of the 060 the
  14     32*32->64 bit result instructions are not supported, and I haven't
  15     quite figured out how to do this using the 32 bit ops yet (can't be
  16     that hard though).
  17
  18     Still, emulating is faster than a unsup integer instruction except.
  19
  20 */
  21
  22     .balign 4
  23
  24     .globl  AROS_SLIB_ENTRY(SMult64,Utility)
  25     .globl  AROS_SLIB_ENTRY(SMult64_020,Utility)
  26
  27     /* Required by SMult64() */
  28     .globl  AROS_SLIB_ENTRY(UMult64,Utility)
  29
  30     .type   AROS_SLIB_ENTRY(SMult64,Utility),@function
  31     .type   AROS_SLIB_ENTRY(SMult64_020,Utility),@function
  32
  33
  34 AROS_SLIB_ENTRY(SMult64_020,Utility):
  35     muls.l  d0,d0:d1
  36     rts
  37
  38 /* How do I do this, again consider:
  39       (a^16 + b) * (c^16 + d)
  40     = ac^32 + (ad + bc)^16 + bd
  41
  42     I tried to think of a way of doing this with the mulu.l instr,
  43     but I couldn't so I'll just use the mulu.w. Its quicker than
  44     an unsupp integer instruction anyway :)
  45 */
  46
  47 /* Have to change the sign... */
  48     .balign 4
  49 AROS_SLIB_ENTRY(SMult64,Utility):
  50     move.l  d2,-(a7)
  51     moveq   #0,d2
  52     tst.l   d0
  53     bpl.s   .ispos1
  54     neg.l   d0
  55     addq.l  #1,d2
  56 .ispos1:
  57     tst.l   d1
  58     bpl.s   .ispos2
  59     neg.l   d1
  60     subq.l  #1,d2
  61
  62     /* Ok, so if d2 != 0, then the sign was changed */
  63 .ispos2:
  64     bsr.s   AROS_SLIB_ENTRY(UMult64,Utility)
  65     tst.l   d0
  66     beq.s   .ispos
  67     moveq   #0,d2
  68
  69     /* Ok we have to change the sign, 2's comp = 1's comp + 1 */
  70     not.l   d0
  71     not.l   d1
  72     /* Add 1 to low order 32 bits */
  73     addq.l  #1,d1
  74     /* Add 0 and the carry to the high 32 bits */
  75     addx.l  d2,d0
  76 .ispos:
  77     move.l  (sp)+,d2
  78     rts
  79