sysdeps/alpha/fpu/s_ceil.c

   1 /* Copyright (C) 1998-2018 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <math.h>
  20 #include <math_ldbl_opt.h>
  21 #include <libm-alias-double.h>
  22
  23 /* Use the -inf rounding mode conversion instructions to implement
  24    ceil, via something akin to -floor(-x).  This is much faster than
  25    playing with the fpcr to achieve +inf rounding mode.  */
  26
  27 double
  28 __ceil (double x)
  29 {
  30   if (isnan (x))
  31     return x + x;
  32
  33   if (isless (fabs (x), 9007199254740992.0))    /* 1 << DBL_MANT_DIG */
  34     {
  35       double tmp1, new_x;
  36
  37       new_x = -x;
  38       __asm (
  39              "cvttq/svm %2,%1\n\t"
  40              "cvtqt/m %1,%0\n\t"
  41              : "=f"(new_x), "=&f"(tmp1)
  42              : "f"(new_x));
  43
  44       /* Fix up the negation we did above, as well as handling -0 properly. */
  45       x = copysign(new_x, x);
  46     }
  47   return x;
  48 }
  49
  50 libm_alias_double (__ceil, ceil)