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Add more math functions (#128)

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dosisod 2021-03-17 20:05:12 -07:00 • committed by GitHub
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commit 8a236433a2
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libc/tinymath/nexttoward.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╚──────────────────────────────────────────────────────────────────────────────╝
│ │
│ Musl Libc │
│ Copyright © 2005-2020 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/math.h"
asm(".ident\t\"\\n\\n\
Musl libc (MIT License)\\n\
Copyright 2005-2020 Rich Felker, et. al.\"");
asm(".include \"libc/disclaimer.inc\"");
/* clang-format off */
static inline void fp_force_eval(double x)
{
volatile double y;
y = x;
}
double nexttoward(double x, long double y)
{
union {double f; uint64_t i;} ux = {x};
int e;
if (isnan(x) || isnan(y))
return x + y;
if (x == y)
return y;
if (x == 0) {
ux.i = 1;
if (signbit(y))
ux.i |= 1ULL<<63;
} else if (x < y) {
if (signbit(x))
ux.i--;
else
ux.i++;
} else {
if (signbit(x))
ux.i++;
else
ux.i--;
}
e = ux.i>>52 & 0x7ff;
/* raise overflow if ux.f is infinite and x is finite */
if (e == 0x7ff)
fp_force_eval(x+x);
/* raise underflow if ux.f is subnormal or zero */
if (e == 0)
fp_force_eval(x*x + ux.f*ux.f);
return ux.f;
}