newlib/libm/machine/riscv/feholdexcept.c

   1 /*
   2   (c) Copyright 2017 Michael R. Neilly
   3   All rights reserved.
   4
   5   Redistribution and use in source and binary forms, with or without
   6   modification, are permitted provided that the following conditions
   7   are met:
   8
   9   * Redistributions of source code must retain the above copyright
  10   notice, this list of conditions and the following disclaimer.
  11
  12   * Redistributions in binary form must reproduce the above copyright
  13   notice, this list of conditions and the following disclaimer in the
  14   documentation and/or other materials provided with the distribution.
  15
  16   * Neither the names of the copyright holders nor the names of their
  17   contributors may be used to endorse or promote products derived from
  18   this software without specific prior written permission.
  19
  20   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  21   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  22   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  23   FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  24   COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  25   INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  26   BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  27   LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  28   CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29   LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  30   ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31   POSSIBILITY OF SUCH DAMAGE.
  32 */
  33
  34 #include <fenv.h>
  35 #include "riscv_math.h"
  36
  37 /* This implementation is intended to comply with the following
  38  * specification:
  39  *
  40  * http://pubs.opengroup.org/onlinepubs/009695399/functions/feholdexcept.html
  41  * Referred to as 'feholdexcept.html below.
  42  *
  43  * "The feholdexcept() function shall save the current floating-point
  44  * environment in the object pointed to by envp, clear the
  45  * floating-point status flags, and then install a non-stop (continue
  46  * on floating-point exceptions) mode, if available, for all
  47  * floating-point exceptions."
  48  */
  49
  50 int feholdexcept(fenv_t *envp)
  51 {
  52
  53 #ifdef __RISCV_HARD_FLOAT
  54
  55   /* Store the current FP environment in envp*/
  56
  57   fenv_t fcsr;
  58   asm volatile("frcsr %0" : "=r"(fcsr));
  59   *envp = fcsr;
  60
  61   /* Clear all flags */
  62
  63   asm volatile("csrrc zero, fflags, %0" : : "r"(FE_ALL_EXCEPT));
  64
  65   /* RISC-V does not raise FP traps so it is always in a "non-stop" mode */
  66
  67   /* Per 'feholdexcept.html:
  68    *
  69    * "The feholdexcept() function shall return zero if and only if
  70    * non-stop floating-point exception handling was successfully
  71    * installed."
  72    */
  73
  74 #endif
  75
  76   return 0;
  77 }