sysdeps/riscv/rv64/rvd/s_trunc.c

   1 /* trunc().  RISC-V version.
   2    Copyright (C) 2017-2020 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #define NO_MATH_REDIRECT
  20 #include <math.h>
  21 #include <fenv_private.h>
  22 #include <libm-alias-double.h>
  23 #include <stdint.h>
  24
  25 double
  26 __trunc (double x)
  27 {
  28   int flags = riscv_getflags ();
  29   bool nan = isnan (x);
  30   double mag = fabs (x);
  31
  32   if (nan)
  33     return x + x;
  34
  35   if (mag < (1ULL << __DBL_MANT_DIG__))
  36     {
  37       int64_t i;
  38       double new_x;
  39
  40       asm volatile ("fcvt.l.d %0, %1, rtz" : "=r" (i) : "f" (x));
  41       asm volatile ("fcvt.d.l %0, %1, rtz" : "=f" (new_x) : "r" (i));
  42
  43       /* trunc(-0) == -0, and in general we'll always have the same
  44          sign as our input.  */
  45       x = copysign (new_x, x);
  46
  47       riscv_setflags (flags);
  48     }
  49
  50   return x;
  51 }
  52
  53 libm_alias_double (__trunc, trunc)