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     FUNCTION
  10       Calculate y raised to the x power (y^x)
  11
  12     RESULT
  13       IEEE double precision floating point number
  14
  15       flags:
  16         zero     : result is zero
  17         negative : result is negative
  18         overflow : result is too big
  19
  20     NOTES
  21
  22     EXAMPLE
  23
  24     BUGS
  25
  26     SEE ALSO
  27
  28     INTERNALS
  29
  30     HISTORY
  31 */
  32
  33 AROS_LHQUAD2(double, IEEEDPPow,
  34     AROS_LHAQUAD(double, x, D2, D3),
  35     AROS_LHAQUAD(double, y, D0, D1),
  36     struct MathIeeeDoubTransBase *, MathIeeeDoubTransBase, 15, MathIeeeDoubTrans
  37 )
  38 {
  39     AROS_LIBFUNC_INIT
  40
  41     /*
  42         a ^ b  = e^(b * ln a)
  43         y ^ x  = e^(x * ln y)
  44     */
  45     QUAD Res, tmp;
  46
  47     /* y^x is illegal if y<0 and x is not an integer-value */
  48     if (is_lessSC(y, 0x0, 0x0) && is_neq(x, IEEEDPCeil(x)))
  49     {
  50         Set_Value64C(Res, 0x0, 0x0);
  51         return Res;
  52     }
  53
  54     if (is_eqC(y, 0x0, 0x0))
  55     {
  56         Set_Value64C(Res, 0x3ff00000, 0x0);
  57         return Res;
  58     }
  59     Set_Value64(tmp, y);
  60     AND64QC
  61     (
  62         tmp,
  63         (IEEEDPMantisse_Mask_Hi + IEEEDPExponent_Mask_Hi),
  64         (IEEEDPMantisse_Mask_Lo + IEEEDPExponent_Mask_Lo)
  65     );
  66
  67     Res = IEEEDPLog(tmp);
  68     Res = IEEEDPMul(Res, x);
  69     Res = IEEEDPExp(Res);
  70
  71     /*
  72         if y < 0 and x was and even integer, the result is positive, otherwise
  73         it is negative.
  74     */
  75     if
  76     (
  77            is_lessSC(y, 0x0, 0x0)
  78         && TRUE == intern_IEEEDPisodd(x)
  79     )
  80     {
  81         OR64QC(Res, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo);
  82     }
  83
  84     if (is_eqC(Res, 0x0, 0x0))
  85     {
  86         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  87         Set_Value64C(Res, 0x0, 0x0);
  88         return Res;
  89     }
  90
  91     SetSR(0, Zero_Bit | Negative_Bit | Overflow_Bit);
  92
  93     if (is_lessSC(Res, 0x0, 0x0))
  94     {
  95         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  96     }
  97
  98     Set_Value64(tmp, Res);
  99     AND64QC
 100     (
 101         tmp,
 102         (IEEEDPMantisse_Mask_Hi + IEEEDPExponent_Mask_Hi),
 103         (IEEEDPMantisse_Mask_Lo + IEEEDPExponent_Mask_Lo)
 104     );
 105
 106     if (is_eqC(Res, IEEEDPPInfty_Hi, IEEEDPPInfty_Lo))
 107     {
 108         /* don`t touch the Negative_Bit now!*/
 109         SetSR(Overflow_Bit, Zero_Bit | Overflow_Bit);
 110     }
 111
 112     return Res;
 113
 114     AROS_LIBFUNC_EXIT
 115 }