rom/utility/umult64.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Unsigned 64-bit product of two 32-bit numbers.
   6     Lang: english
   7 */
   8 #include "intern.h"
   9
  10 /*****************************************************************************
  11
  12     NAME */
  13 #include <proto/utility.h>
  14
  15         AROS_LH2(UQUAD, UMult64,
  16
  17 /*  SYNOPSIS */
  18         AROS_LHA(ULONG, arg1, D0),
  19         AROS_LHA(ULONG, arg2, D1),
  20
  21 /*  LOCATION */
  22         struct UtilityBase *, UtilityBase, 34, Utility)
  23
  24 /*  FUNCTION
  25         Compute the unsigned 64-bit product of arg1 * arg2.
  26
  27     INPUTS
  28         arg1, arg2  -   32 bit unsigned numbers.
  29
  30     RESULT
  31         arg1 * arg2
  32
  33     NOTES
  34         For m68k assembly programmers, UQUADs are returned in D0:D1 (with
  35         the high 32 bits in D0.
  36
  37         This function is really only for people programming in
  38         assembly on real Amigas. Most compilers will be able to do this
  39         math for you inline.
  40
  41     EXAMPLE
  42
  43     BUGS
  44
  45     SEE ALSO
  46         SMult32(), UMult32(), SMult64()
  47
  48     INTERNALS
  49         This may or may not be handled by code in config/$(KERNEL),
  50         for m68k-native it is...
  51
  52         This is essentially UMult32(), but with the code to calculate
  53         the product of the high 32 bits of the multiplicands.
  54
  55     HISTORY
  56         29-10-95    digulla automatically created from
  57                             utility_lib.fd and clib/utility_protos.h
  58         18-08-96    iaint   Modified UMult32().
  59
  60 *****************************************************************************/
  61 {
  62     AROS_LIBFUNC_INIT
  63
  64     /* If we have native support for 32 * 32 -> 64, use that. */
  65     return (UQUAD)arg1 * arg2;
  66
  67
  68 #if 0
  69     /* This is partially the algoritm that is used, however for a
  70        more complete version see config/m68k-native/smult64.s
  71
  72        This version has problems with:
  73         - adding the partial products together
  74         - setting the value of QUADs
  75     */
  76
  77     UQUAD product;
  78     UWORD a0, a1, b0, b1;
  79     ULONG part_prod;
  80
  81     a1 = (arg1 >> 16) & 0xffff;
  82     a0 = arg1 & 0xffff;
  83     b1 = (arg2 >> 16) & 0xffff;
  84     b0 = arg2 & 0xffff;
  85
  86     part_prod = (a0 * b1) + (a1 * b0);
  87
  88     SET_HIGH32OF64(product, (part_prod >> 16) + (a1 * b1));
  89     SET_LOW32OF64(product, ((part_prod & 0xFFFF) << 16) + (a0 * b0));
  90
  91     return product;
  92 #endif
  93
  94     AROS_LIBFUNC_EXIT
  95 } /* UMult64 */