File: s_ceil.c

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/* Copyright (C) 1998-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Richard Henderson.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library.  If not, see
   <http://www.gnu.org/licenses/>.  */

#include <math.h>
#include <math_ldbl_opt.h>

/* Use the -inf rounding mode conversion instructions to implement
   ceil, via something akin to -floor(-x).  This is much faster than
   playing with the fpcr to achieve +inf rounding mode.  */

double
__ceil (double x)
{
  if (isnan (x))
    return x + x;

  if (isless (fabs (x), 9007199254740992.0))	/* 1 << DBL_MANT_DIG */
    {
      double tmp1, new_x;

      new_x = -x;
      __asm (
	     "cvttq/svm %2,%1\n\t"
	     "cvtqt/m %1,%0\n\t"
	     : "=f"(new_x), "=&f"(tmp1)
	     : "f"(new_x));

      /* Fix up the negation we did above, as well as handling -0 properly. */
      x = copysign(new_x, x);
    }
  return x;
}

weak_alias (__ceil, ceil)
#ifdef NO_LONG_DOUBLE
strong_alias (__ceil, __ceill)
weak_alias (__ceil, ceill)
#endif
#if LONG_DOUBLE_COMPAT(libm, GLIBC_2_0)
compat_symbol (libm, __ceil, ceill, GLIBC_2_0);
#endif