math/math-underflow.h

   1 /* Check for underflow and force underflow exceptions.
   2    Copyright (C) 2015-2021 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 #ifndef _MATH_UNDERFLOW_H
  20 #define _MATH_UNDERFLOW_H       1
  21
  22 #include <float.h>
  23 #include <math.h>
  24
  25 #include <math-barriers.h>
  26
  27 #define fabs_tg(x) __MATH_TG ((x), (__typeof (x)) __builtin_fabs, (x))
  28
  29 /* These must be function-like macros because some __MATH_TG
  30    implementations macro-expand the function-name argument before
  31    concatenating a suffix to it.  */
  32 #define min_of_type_f() FLT_MIN
  33 #define min_of_type_() DBL_MIN
  34 #define min_of_type_l() LDBL_MIN
  35 #define min_of_type_f128() FLT128_MIN
  36
  37 #define min_of_type(x) __MATH_TG ((x), (__typeof (x)) min_of_type_, ())
  38
  39 /* If X (which is not a NaN) is subnormal, force an underflow
  40    exception.  */
  41 #define math_check_force_underflow(x)                           \
  42   do                                                            \
  43     {                                                           \
  44       __typeof (x) force_underflow_tmp = (x);                   \
  45       if (fabs_tg (force_underflow_tmp)                         \
  46           < min_of_type (force_underflow_tmp))                  \
  47         {                                                       \
  48           __typeof (force_underflow_tmp) force_underflow_tmp2   \
  49             = force_underflow_tmp * force_underflow_tmp;        \
  50           math_force_eval (force_underflow_tmp2);               \
  51         }                                                       \
  52     }                                                           \
  53   while (0)
  54 /* Likewise, but X is also known to be nonnegative.  */
  55 #define math_check_force_underflow_nonneg(x)                    \
  56   do                                                            \
  57     {                                                           \
  58       __typeof (x) force_underflow_tmp = (x);                   \
  59       if (force_underflow_tmp                                   \
  60           < min_of_type (force_underflow_tmp))                  \
  61         {                                                       \
  62           __typeof (force_underflow_tmp) force_underflow_tmp2   \
  63             = force_underflow_tmp * force_underflow_tmp;        \
  64           math_force_eval (force_underflow_tmp2);               \
  65         }                                                       \
  66     }                                                           \
  67   while (0)
  68 /* Likewise, for both real and imaginary parts of a complex
  69    result.  */
  70 #define math_check_force_underflow_complex(x)                           \
  71   do                                                                    \
  72     {                                                                   \
  73       __typeof (x) force_underflow_complex_tmp = (x);                   \
  74       math_check_force_underflow (__real__ force_underflow_complex_tmp); \
  75       math_check_force_underflow (__imag__ force_underflow_complex_tmp); \
  76     }                                                                   \
  77   while (0)
  78
  79 #endif /* math-underflow.h */