workbench/libs/mathieeedoubtrans/ieeedppow.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_LHQUAD2(double, IEEEDPPow,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHAQUAD(double, x, D2, D3),
  16         AROS_LHAQUAD(double, y, D0, D1),
  17
  18 /*  LOCATION */
  19         struct MathIeeeDoubTransBase *, MathIeeeDoubTransBase, 15, MathIeeeDoubTrans)
  20
  21 /*  FUNCTION
  22         Calculate y raised to the x power (y^x)
  23
  24     INPUTS
  25
  26     RESULT
  27         IEEE double precision floating point number
  28
  29         flags:
  30         zero     : result is zero
  31         negative : result is negative
  32         overflow : result is too big
  33
  34     BUGS
  35
  36     INTERNALS
  37
  38 *****************************************************************************/
  39 {
  40     AROS_LIBFUNC_INIT
  41
  42     /*
  43         a ^ b  = e^(b * ln a)
  44         y ^ x  = e^(x * ln y)
  45     */
  46     QUAD Res, tmp;
  47
  48     /* y^x is illegal if y<0 and x is not an integer-value */
  49     if (is_lessSC(y, 0x0, 0x0) && is_neq(x, IEEEDPCeil(x)))
  50     {
  51         Set_Value64C(Res, 0x0, 0x0);
  52         return Res;
  53     }
  54
  55     if (is_eqC(y, 0x0, 0x0))
  56     {
  57         Set_Value64C(Res, 0x3ff00000, 0x0);
  58         return Res;
  59     }
  60     Set_Value64(tmp, y);
  61     AND64QC
  62     (
  63         tmp,
  64         (IEEEDPMantisse_Mask_Hi + IEEEDPExponent_Mask_Hi),
  65         (IEEEDPMantisse_Mask_Lo + IEEEDPExponent_Mask_Lo)
  66     );
  67
  68     Res = IEEEDPLog(tmp);
  69     Res = IEEEDPMul(Res, x);
  70     Res = IEEEDPExp(Res);
  71
  72     /*
  73         if y < 0 and x was and even integer, the result is positive, otherwise
  74         it is negative.
  75     */
  76     if
  77     (
  78            is_lessSC(y, 0x0, 0x0)
  79         && TRUE == intern_IEEEDPisodd(x)
  80     )
  81     {
  82         OR64QC(Res, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo);
  83     }
  84
  85     if (is_eqC(Res, 0x0, 0x0))
  86     {
  87         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  88         Set_Value64C(Res, 0x0, 0x0);
  89         return Res;
  90     }
  91
  92     SetSR(0, Zero_Bit | Negative_Bit | Overflow_Bit);
  93
  94     if (is_lessSC(Res, 0x0, 0x0))
  95     {
  96         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  97     }
  98
  99     Set_Value64(tmp, Res);
 100     AND64QC
 101     (
 102         tmp,
 103         (IEEEDPMantisse_Mask_Hi + IEEEDPExponent_Mask_Hi),
 104         (IEEEDPMantisse_Mask_Lo + IEEEDPExponent_Mask_Lo)
 105     );
 106
 107     if (is_eqC(Res, IEEEDPPInfty_Hi, IEEEDPPInfty_Lo))
 108     {
 109         /* don`t touch the Negative_Bit now!*/
 110         SetSR(Overflow_Bit, Zero_Bit | Overflow_Bit);
 111     }
 112
 113     return Res;
 114
 115     AROS_LIBFUNC_EXIT
 116 }