lib/test_fpu_impl.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2
   3 #include <linux/errno.h>
   4
   5 #include "test_fpu.h"
   6
   7 int test_fpu(void)
   8 {
   9         /*
  10          * This sequence of operations tests that rounding mode is
  11          * to nearest and that denormal numbers are supported.
  12          * Volatile variables are used to avoid compiler optimizing
  13          * the calculations away.
  14          */
  15         volatile double a, b, c, d, e, f, g;
  16
  17         a = 4.0;
  18         b = 1e-15;
  19         c = 1e-310;
  20
  21         /* Sets precision flag */
  22         d = a + b;
  23
  24         /* Result depends on rounding mode */
  25         e = a + b / 2;
  26
  27         /* Denormal and very large values */
  28         f = b / c;
  29
  30         /* Depends on denormal support */
  31         g = a + c * f;
  32
  33         if (d > a && e > a && g > a)
  34                 return 0;
  35         else
  36                 return -EINVAL;
  37 }