rom/mathffp/spmul.c

   1 /*
   2     Copyright © 1995-2004, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathffp_intern.h"
   7
   8 /*
   9     FUNCTION
  10         Multiply two ffp numbers
  11         fnum = fnum1 * fnum2;
  12
  13     RESULT
  14         FFP number
  15
  16         Flags:
  17           zero     : result is zero
  18           negative : result is negative
  19           overflow : result is out of range
  20
  21     NOTES
  22
  23     EXAMPLE
  24
  25     BUGS
  26
  27     SEE ALSO
  28
  29     INTERNALS
  30
  31     HISTORY
  32 */
  33
  34 AROS_LH2(float, SPMul,
  35     AROS_LHA(float, fnum1, D1),
  36     AROS_LHA(float, fnum2, D0),
  37     struct LibHeader *, MathBase, 13, Mathffp
  38 )
  39 {
  40     AROS_LIBFUNC_INIT
  41
  42     char Exponent = ((char) fnum1 & FFPExponent_Mask)
  43                   + ((char) fnum2 & FFPExponent_Mask) - 0x41;
  44     ULONG Mant1H = ( (ULONG) (fnum1 & FFPMantisse_Mask)) >> 20;
  45     ULONG Mant2H = ( (ULONG) (fnum2 & FFPMantisse_Mask)) >> 20;
  46     ULONG Mant1L = (((ULONG) (fnum1 & FFPMantisse_Mask)) >> 8) & 0x00000fff;
  47     ULONG Mant2L = (((ULONG) (fnum2 & FFPMantisse_Mask)) >> 8) & 0x00000fff;
  48     LONG Res;
  49
  50     Res  =  (Mant1H * Mant2H) <<  8;
  51     Res += ((Mant1H * Mant2L) >>  4);
  52     Res += ((Mant1L * Mant2H) >>  4);
  53     Res += ((Mant1L * Mant2L) >> 16);
  54
  55     /* Bit 32 is not set */
  56     if ((LONG)Res > 0)
  57     {
  58         Res <<= 1; /* rotate the mantisse by one bit to the left */
  59     }
  60     else
  61     {
  62         Exponent ++;
  63     }
  64
  65     if (0 == Res)
  66     {
  67         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  68         return 0;
  69     }
  70
  71     Res |= ((fnum1 & FFPSign_Mask) ^ (fnum2 & FFPSign_Mask) );
  72
  73     /* overflow? */
  74     if ((char) Exponent < 0 || (char) Exponent == 0x7f)
  75     {
  76         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  77         kprintf("%x * %x = %x\n",fnum1,fnum2,Res);
  78         return (Res | (FFPMantisse_Mask + FFPExponent_Mask));
  79     }
  80
  81     Res |= Exponent;
  82
  83     if ((char) Res < 0)
  84     {
  85         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  86     }
  87
  88     kprintf("%x * %x = %x\n",fnum1,fnum2,Res);
  89
  90     return Res;
  91
  92     AROS_LIBFUNC_EXIT
  93 }