sysdeps/powerpc/q_qtoi.c

   1 /* 128-bit floating point to 32-bit fixed point signed 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 /* int _q_qtoi(const long double *a);
  23    Convert 'a' to signed int by truncation.
  24
  25    Special cases:
  26    NaN: raise VXCVI, return 0x80000000
  27    SNaN: raise VXSNAN, VXCVI, and return 0x80000000
  28    >= 2^32: raise VXCVI, return 0x7fffffff
  29    <= -2^32: raise VXCVI, return 0x80000000
  30    */
  31
  32 int
  33 __q_qtoi(const unsigned long long a[2])
  34 {
  35   int ax, sgn;
  36   unsigned long long a0;
  37
  38   a0 = a[0];
  39   /* 'sgn' is -1 if 'a' is negative, 0 if positive.  */
  40   sgn = (long long)a0 >> 63;
  41   ax = (a0 >> 48 & 0x7fff) - 16383;
  42   /* Deal with non-special cases.  */
  43   if (ax <= 30)
  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.  The '^ sgn) - sgn' part is
  47        equivalent in this case to multiplication by 'sgn', but usually
  48        faster.  */
  49     return (((unsigned)(a0 >> 17  |  0x80000000) >> 31-ax  &  -(ax >> 31))
  50             ^ sgn) - sgn;
  51
  52   /* Check for SNaN, if so raise VXSNAN.  */
  53   if ((a0 >> 32  &  0x7fff8000) == 0x7fff0000
  54       && (a[1]  |  a0 & 0x00007fffffffffffULL) != 0)
  55     set_fpscr_bit(FPSCR_VXSNAN);
  56
  57   /* Treat all NaNs as large negative numbers.  */
  58   sgn |= -cntlzw(~(a0 >> 32)  &  0x7fff0000) >> 5;
  59
  60   /* All the specials raise VXCVI.  */
  61   set_fpscr_bit(FPSCR_VXCVI);
  62
  63   /* Return 0x7fffffff (if a < 0) or 0x80000000 (otherwise).  */
  64   return sgn ^ 0x7fffffff;
  65 }