workbench/libs/mathieeedoubbas/ieeedpneg.c

   1 /*
   2     Copyright © 1995-2017, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeedoubbas_intern.h"
   7
   8 /*****************************************************************************
   9
  10     NAME */
  11
  12         AROS_LHQUAD1(double, IEEEDPNeg,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHAQUAD(double, y, D0, D1),
  16
  17 /*  LOCATION */
  18         struct MathIeeeDoubBasBase *, MathIeeeDoubBasBase, 10, MathIeeeDoubBas)
  19
  20 /*  FUNCTION
  21         Switches the sign of the given IEEE double precision floating point
  22         number.
  23
  24     INPUTS
  25         y - IEEE double precision floating point number.
  26
  27     RESULT
  28         x - the negation of y.
  29
  30         Flags:
  31           zero     : result is zero
  32           negative : result is negative
  33           overflow : 0
  34
  35     NOTES
  36
  37     EXAMPLE
  38
  39     BUGS
  40
  41     SEE ALSO
  42         IEEEDPAbs()
  43
  44     INTERNALS
  45         Algorithm:
  46         Flip the sign-bit (even for zeroes).
  47
  48 *****************************************************************************/
  49 {
  50     AROS_LIBFUNC_INIT
  51
  52     QUAD * Qy = (QUAD *)&y;
  53
  54     /* change the sign-bit */
  55     XOR64QC(*Qy, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo);
  56
  57     if
  58     (
  59            is_eqC(*Qy, 0x0, 0x0 )
  60         || is_eqC(*Qy, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo)
  61     )
  62     {
  63         SetSR( Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  64         return y;
  65     }
  66
  67     /* if (y < 0) */
  68     if(is_lessSC(*Qy, 0x0, 0x0) )
  69     {
  70         /* result is negative */
  71         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  72     }
  73     else
  74     {
  75         /* result is positive */
  76         SetSR(0, Zero_Bit | Overflow_Bit | Negative_Bit );
  77     }
  78
  79     return y;
  80
  81     AROS_LIBFUNC_EXIT
  82 }