1/* Copyright (C) 2011-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <fenv.h>
19#include <math.h>
20#include <math_private.h>
21#include <math-svid-compat.h>
22#include <libm-alias-float.h>
23
24
25#if LIBM_SVID_COMPAT && SHLIB_COMPAT (libm, GLIBC_2_1, GLIBC_2_27)
26/* wrapper log2f(x) */
27float
28__log2f_compat (float x)
29{
30 if (__builtin_expect (islessequal (x, 0.0f), 0) && _LIB_VERSION != _IEEE_)
31 {
32 if (x == 0.0)
33 {
34 feraiseexcept (FE_DIVBYZERO);
35 return __kernel_standard_f (x, x, 148); /* log2(0) */
36 }
37 else
38 {
39 feraiseexcept (FE_INVALID);
40 return __kernel_standard_f (x, x, 149); /* log2(x<0) */
41 }
42 }
43
44 return __ieee754_log2f (x);
45}
46compat_symbol (libm, __log2f_compat, log2f, GLIBC_2_1);
47#endif
48

source code of glibc/math/w_log2f_compat.c