sysdeps/powerpc/q_qtou.c

   1 /* 128-bit floating point to 32-bit fixed point unsigned integer.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <quad_float.h>
  21
  22 /* unsigned int _q_qtou(const long double *a);
  23    Convert 'a' to unsigned int by truncation.
  24
  25    Special cases:
  26    -0: return 0
  27    NaN: raise VXCVI, return 0
  28    SNaN: raise VXSNAN, VXCVI, and return 0
  29    Negative numbers (other than -0, but including -Inf): raise VXCVI, return 0
  30    >= 2^32: raise VXCVI, return 0xffffffff
  31    */
  32
  33 unsigned int
  34 __q_qtou(const unsigned long long a[2])
  35 {
  36   int ax;
  37   unsigned result;
  38   unsigned long long a0;
  39
  40   /* Deal with non-special cases.  */
  41   a0 = a[0];
  42   ax = (a0 >> 48) - 16383;
  43   if (ax <= 31)
  44     /* If we had a '>>' operator that behaved properly with respect to
  45        large shifts, we wouldn't need the '& -(ax >> 31)' term, which
  46        clears 'result' if ax is negative.  */
  47     return (unsigned)(a0 >> 17  |  0x80000000) >> 31-ax  &  -(ax >> 31);
  48
  49   /* 'result' is 1 if a is negative, 0 otherwise.  */
  50   result = a0 >> 63;
  51   /* Check for -0, otherwise raise VXCVI.  */
  52   if (a0 != 0x8000000000000000ULL  ||  a[1] != 0)
  53   {
  54     /* Check for SNaN, if so raise VXSNAN.  */
  55     if ((a0 >> 32  &  0x7fff8000) == 0x7fff0000
  56         && (a[1]  |  a0 & 0x00007fffffffffffULL) != 0)
  57       set_fpscr_bit(FPSCR_VXSNAN);
  58     /* Treat all NaNs as large negative numbers.  */
  59     result |= cntlzw(~(a0 >> 32)  &  0x7fff0000) >> 5;
  60
  61     set_fpscr_bit(FPSCR_VXCVI);
  62   }
  63   return result-1;
  64 }