sysdeps/riscv/rv64/rvd/s_roundeven.c

   1 /* Round to nearest integer value, rounding halfway cases to even.
   2    Copyright (C) 2017-2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 <fenv_private.h>
  21 #include <libm-alias-double.h>
  22 #include <stdint.h>
  23
  24 double
  25 __roundeven (double x)
  26 {
  27   int flags = riscv_getflags ();
  28   bool nan = isnan (x);
  29   double mag = fabs (x);
  30
  31   if (nan)
  32     return x + x;
  33
  34   if (mag < (1ULL << __DBL_MANT_DIG__))
  35     {
  36       int64_t i;
  37       double new_x;
  38
  39       asm volatile ("fcvt.l.d %0, %1, rne" : "=r" (i) : "f" (x));
  40       asm volatile ("fcvt.d.l %0, %1, rne" : "=f" (new_x) : "r" (i));
  41
  42       /* roundeven(-0) == -0, and in general we'll always have the same
  43          sign as our input.  */
  44       x = copysign (new_x, x);
  45
  46       riscv_setflags (flags);
  47     }
  48
  49   return x;
  50 }
  51
  52 hidden_def (__roundeven)
  53 libm_alias_double (__roundeven, roundeven)