sysdeps/alpha/fpu/s_trunc.c

   1 /* Copyright (C) 2007-2017 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
  22
  23 /* Use the chopped rounding mode conversion instructions to implement trunc. */
  24
  25 double
  26 __trunc (double x)
  27 {
  28   double two52 = copysign (0x1.0p52, x);
  29   double r, tmp;
  30
  31   if (isgreaterequal (fabs (x), 0x1.0p52))
  32     return x;
  33
  34   __asm (
  35          "addt/suc %2, %3, %1\n\tsubt/suc %1, %3, %0"
  36          : "=&f"(r), "=&f"(tmp)
  37          : "f"(x), "f"(two52));
  38
  39   /* trunc(-0) == -0, and in general we'll always have the same
  40      sign as our input.  */
  41   return copysign (r, x);
  42 }
  43
  44 weak_alias (__trunc, trunc)
  45 #ifdef NO_LONG_DOUBLE
  46 strong_alias (__trunc, __truncl)
  47 weak_alias (__trunc, truncl)
  48 #endif
  49 #if LONG_DOUBLE_COMPAT(libm, GLIBC_2_1)
  50 compat_symbol (libm, __trunc, truncl, GLIBC_2_1);
  51 #endif