workbench/libs/mathieeedoubtrans/ieeedptanh.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeedoubtrans_intern.h"
   7
   8 /*****************************************************************************
   9
  10     NAME */
  11
  12         AROS_LHQUAD1(double, IEEEDPTanh,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHAQUAD(double, y, D0, D1),
  16
  17 /*  LOCATION */
  18         struct MathIeeeDoubTransBase *, MathIeeeDoubTransBase, 12, MathIeeeDoubTrans)
  19
  20 /*  FUNCTION
  21         Calculate hyperbolic tangens of the IEEE double precision number
  22
  23     INPUTS
  24
  25     RESULT
  26         IEEE double precision floating point number
  27
  28         flags:
  29         zero     : result is zero
  30         negative : result is negative
  31         overflow : (not possible)
  32
  33     BUGS
  34
  35     INTERNALS
  36                    ( e^x - e^(-x) )
  37         tanh(x) =  ----------------
  38                    ( e^x + e^(-x) )
  39
  40         tanh( |x| >= 18 ) = 1
  41
  42 *****************************************************************************/
  43 {
  44     AROS_LIBFUNC_INIT
  45
  46     QUAD Res;
  47     QUAD y2;
  48     /* y2 = y & (IEEESPMantisse_Mask + IEEESPExponent_Mask ); */
  49     Set_Value64(y2, y);
  50     AND64QC
  51     (
  52         y2,
  53         (IEEEDPMantisse_Mask_Hi + IEEEDPExponent_Mask_Hi),
  54         (IEEEDPMantisse_Mask_Lo + IEEEDPExponent_Mask_Lo)
  55     );
  56
  57     if ( is_geqC(y2, 0x40320000, 0x0) )
  58     {
  59         /*
  60             tanh( x > 18 ) =  1
  61             tanh( x <-18 ) = -1
  62         */
  63         if ( is_lessSC(y, 0x0, 0x0))
  64         {
  65             SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  66             Set_Value64C(Res, 0xbfefffff, 0xffffffff);
  67         }
  68         else
  69         {
  70             Set_Value64C(Res, 0x3fefffff, 0xffffffff);
  71         }
  72         return Res;
  73     }
  74     /* tanh(-x) = -tanh(x) */
  75     {
  76         QUAD One, tmp1, tmp2;
  77         Set_Value64C(One, 0x3ff00000, 0x0);
  78
  79         Res = IEEEDPExp(y2);
  80         tmp1 = IEEEDPDiv(One, Res);
  81         Set_Value64(tmp2, tmp1);
  82         OR64QC(tmp2, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo);
  83         Res = IEEEDPDiv
  84         (
  85             IEEEDPAdd(Res, tmp2),
  86             IEEEDPAdd(Res, tmp1)
  87         );
  88     }
  89     /* Result is zero */
  90     if (is_eqC(Res, 0x0, 0x0) )
  91     {
  92         if (is_lessSC(y, 0x0, 0x0))
  93         {
  94             SetSR
  95             (
  96                   Zero_Bit | Negative_Bit,
  97                   Zero_Bit | Negative_Bit | Overflow_Bit
  98             );
  99         }
 100         else
 101         {
 102             SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
 103         }
 104         return Res;
 105     }
 106
 107     /* Argument is negative -> result is negative */
 108     if ( is_lessSC(y, 0x0, 0x0))
 109     {
 110         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
 111         OR64QC(Res, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo);
 112         return Res;
 113     }
 114
 115     return Res;
 116
 117     AROS_LIBFUNC_EXIT
 118 }