sysdeps/alpha/fpu/s_trunc.c

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