File: s_trunc.c

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glibc 2.24-11+deb9u4
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/* Copyright (C) 2007-2016 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 chopped rounding mode conversion instructions to implement trunc. */

double
__trunc (double x)
{
  double two52 = copysign (0x1.0p52, x);
  double r, tmp;

  if (isgreaterequal (fabs (x), 0x1.0p52))
    return x;

  __asm (
	 "addt/suc %2, %3, %1\n\tsubt/suc %1, %3, %0"
	 : "=&f"(r), "=&f"(tmp)
	 : "f"(x), "f"(two52));

  /* trunc(-0) == -0, and in general we'll always have the same
     sign as our input.  */
  return copysign (r, x);
}

weak_alias (__trunc, trunc)
#ifdef NO_LONG_DOUBLE
strong_alias (__trunc, __truncl)
weak_alias (__trunc, truncl)
#endif
#if LONG_DOUBLE_COMPAT(libm, GLIBC_2_1)
compat_symbol (libm, __trunc, truncl, GLIBC_2_1);
#endif