sysdeps/alpha/fpu/s_floor.c

   1 /* Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Richard Henderson.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <math.h>
  21
  22
  23 /* Use the -inf rounding mode conversion instructions to implement
  24    floor.  We note when the exponent is large enough that the value
  25    must be integral, as this avoids unpleasant integer overflows.  */
  26
  27 double
  28 __floor (double x)
  29 {
  30   if (isless (fabs (x), 9007199254740992.0))    /* 1 << DBL_MANT_DIG */
  31     {
  32       double tmp1, new_x;
  33
  34       __asm (
  35 #ifdef _IEEE_FP_INEXACT
  36              "cvttq/svim %2,%1\n\t"
  37 #else
  38              "cvttq/svm %2,%1\n\t"
  39 #endif
  40              "cvtqt/m %1,%0\n\t"
  41              : "=f"(new_x), "=&f"(tmp1)
  42              : "f"(x));
  43
  44       /* floor(-0) == -0, and in general we'll always have the same
  45          sign as our input.  */
  46       x = copysign(new_x, x);
  47     }
  48   return x;
  49 }
  50
  51 weak_alias (__floor, floor)
  52 #ifdef NO_LONG_DOUBLE
  53 strong_alias (__floor, __floorl)
  54 weak_alias (__floor, floorl)
  55 #endif