mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 11:37:35 +00:00
166 lines
6.6 KiB
C
166 lines
6.6 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
|
||
│vi: set et ft=c ts=8 tw=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/math.h"
|
||
#include "libc/runtime/fenv.h"
|
||
|
||
asm(".ident\t\"\\n\\n\
|
||
Fused Multiply Add (MIT License)\\n\
|
||
Copyright (c) 2005-2011 David Schultz <das@FreeBSD.ORG>\"");
|
||
asm(".ident\t\"\\n\\n\
|
||
Musl libc (MIT License)\\n\
|
||
Copyright 2005-2014 Rich Felker, et. al.\"");
|
||
asm(".include \"libc/disclaimer.inc\"");
|
||
// clang-format off
|
||
|
||
/* origin: FreeBSD /usr/src/lib/msun/src/s_fmaf.c */
|
||
/*-
|
||
* Copyright (c) 2005-2011 David Schultz <das@FreeBSD.ORG>
|
||
* All rights reserved.
|
||
*
|
||
* Redistribution and use in source and binary forms, with or without
|
||
* modification, are permitted provided that the following conditions
|
||
* are met:
|
||
* 1. Redistributions of source code must retain the above copyright
|
||
* notice, this list of conditions and the following disclaimer.
|
||
* 2. Redistributions in binary form must reproduce the above copyright
|
||
* notice, this list of conditions and the following disclaimer in the
|
||
* documentation and/or other materials provided with the distribution.
|
||
*
|
||
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
||
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
||
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
||
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
||
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
||
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
||
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
||
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
||
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||
* SUCH DAMAGE.
|
||
*/
|
||
|
||
/**
|
||
* Performs fused multiply add.
|
||
*
|
||
* @return `𝑥 * 𝑦 + 𝑧` with a single rounding error
|
||
*/
|
||
float fmaf(float x, float y, float z)
|
||
{
|
||
#if defined(__x86_64__) && defined(__FMA__)
|
||
|
||
// Intel Haswell+ (c. 2013)
|
||
// AMD Piledriver+ (c. 2011)
|
||
asm("vfmadd132ss\t%1,%2,%0" : "+x"(x) : "x"(y), "x"(z));
|
||
return x;
|
||
|
||
#elif defined(__x86_64__) && defined(__FMA4__)
|
||
|
||
// AMD Bulldozer+ (c. 2011)
|
||
asm("vfmaddss\t%3,%2,%1,%0" : "=x"(x) : "x"(x), "x"(y), "x"(z));
|
||
return x;
|
||
|
||
#elif defined(__aarch64__)
|
||
|
||
asm("fmadd\t%s0,%s1,%s2,%s3" : "=w"(x) : "w"(x), "w"(y), "w"(z));
|
||
return x;
|
||
|
||
#elif defined(__powerpc64__)
|
||
|
||
asm("fmadds\t%0,%1,%2,%3" : "=f"(x) : "f"(x), "f"(y), "f"(z));
|
||
return x;
|
||
|
||
#elif defined(__riscv) && __riscv_flen >= 32
|
||
|
||
asm("fmadd.s\t%0,%1,%2,%3" : "=f"(x) : "f"(x), "f"(y), "f"(z));
|
||
return x;
|
||
|
||
#elif defined(__s390x__)
|
||
|
||
asm("maebr\t%0,%1,%2" : "+f"(z) : "f"(x), "f"(y));
|
||
return z;
|
||
|
||
#else
|
||
|
||
/* A double has more than twice as much precision than a float,
|
||
so direct double-precision arithmetic suffices, except where
|
||
double rounding occurs. */
|
||
|
||
/* #pragma STDC FENV_ACCESS ON */
|
||
double xy, result;
|
||
union {double f; uint64_t i;} u;
|
||
int e;
|
||
|
||
xy = (double)x * y;
|
||
result = xy + z;
|
||
u.f = result;
|
||
e = u.i>>52 & 0x7ff;
|
||
/* Common case: The double precision result is fine. */
|
||
if ((u.i & 0x1fffffff) != 0x10000000 || /* not a halfway case */
|
||
e == 0x7ff || /* NaN */
|
||
(result - xy == z && result - z == xy) || /* exact */
|
||
fegetround() != FE_TONEAREST) /* not round-to-nearest */
|
||
{
|
||
/*
|
||
underflow may not be raised correctly, example:
|
||
fmaf(0x1p-120f, 0x1p-120f, 0x1p-149f)
|
||
*/
|
||
#if defined(FE_INEXACT) && defined(FE_UNDERFLOW)
|
||
if (e < 0x3ff-126 && e >= 0x3ff-149 && fetestexcept(FE_INEXACT)) {
|
||
feclearexcept(FE_INEXACT);
|
||
/* TODO: gcc and clang bug workaround */
|
||
volatile float vz = z;
|
||
result = xy + vz;
|
||
if (fetestexcept(FE_INEXACT))
|
||
feraiseexcept(FE_UNDERFLOW);
|
||
else
|
||
feraiseexcept(FE_INEXACT);
|
||
}
|
||
#endif
|
||
z = result;
|
||
return z;
|
||
}
|
||
|
||
/*
|
||
* If result is inexact, and exactly halfway between two float values,
|
||
* we need to adjust the low-order bit in the direction of the error.
|
||
*/
|
||
double err;
|
||
int neg = u.i >> 63;
|
||
if (neg == (z > xy))
|
||
err = xy - result + z;
|
||
else
|
||
err = z - result + xy;
|
||
if (neg == (err < 0))
|
||
u.i++;
|
||
else
|
||
u.i--;
|
||
z = u.f;
|
||
return z;
|
||
|
||
#endif /* __x86_64__ */
|
||
}
|