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ilogbl.c
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ilogbl.c
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/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8 :vi │
╚──────────────────────────────────────────────────────────────────────────────╝
│ │
│ Musl Libc │
│ Copyright © 2005-2014 Rich Felker, et al. │
│ │
│ Permission is hereby granted, free of charge, to any person obtaining │
│ a copy of this software and associated documentation files (the │
│ "Software"), to deal in the Software without restriction, including │
│ without limitation the rights to use, copy, modify, merge, publish, │
│ distribute, sublicense, and/or sell copies of the Software, and to │
│ permit persons to whom the Software is furnished to do so, subject to │
│ the following conditions: │
│ │
│ The above copyright notice and this permission notice shall be │
│ included in all copies or substantial portions of the Software. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, │
│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF │
│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. │
│ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY │
│ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, │
│ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE │
│ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. │
│ │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/limits.h"
#include "libc/math.h"
#include "libc/tinymath/internal.h"
#include "libc/tinymath/ldshape.internal.h"
#if !(LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024)
__static_yoink("musl_libc_notice");
/**
* Returns log₂𝑥 exponent part of double.
*/
int ilogbl(long double x)
{
#if LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
// #pragma STDC FENV_ACCESS ON
union ldshape u = {x};
uint64_t m = u.i.m;
int e = u.i.se & 0x7fff;
if (!e) {
if (m == 0) {
FORCE_EVAL(0/0.0f);
return FP_ILOGB0;
}
/* subnormal x */
for (e = -0x3fff+1; m>>63 == 0; e--, m<<=1);
return e;
}
if (e == 0x7fff) {
FORCE_EVAL(0/0.0f);
return m<<1 ? FP_ILOGBNAN : INT_MAX;
}
return e - 0x3fff;
#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
// #pragma STDC FENV_ACCESS ON
union ldshape u = {x};
int e = u.i.se & 0x7fff;
if (!e) {
if (x == 0) {
FORCE_EVAL(0/0.0f);
return FP_ILOGB0;
}
/* subnormal x */
x *= 0x1p120;
return ilogbl(x) - 120;
}
if (e == 0x7fff) {
FORCE_EVAL(0/0.0f);
u.i.se = 0;
return u.f ? FP_ILOGBNAN : INT_MAX;
}
return e - 0x3fff;
#endif
}
#endif /* long double is long */