mirror of
https://github.com/jart/cosmopolitan.git
synced 2024-05-18 03:22:40 +00:00
592f6ebc20
- Write some more unit tests - memcpy() on ARM is now faster - Address the Musl complex math FIXME comments - Some libm funcs like pow() now support setting errno - Import the latest and greatest math functions from ARM - Use more accurate atan2f() and log1pf() implementations - atoi() and atol() will no longer saturate or clobber errno
107 lines
4.5 KiB
C
107 lines
4.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
|
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
|
|
╚──────────────────────────────────────────────────────────────────────────────╝
|
|
│ │
|
|
│ Optimized Routines │
|
|
│ Copyright (c) 2018-2024, Arm Limited. │
|
|
│ │
|
|
│ 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/tinymath/arm.internal.h"
|
|
__static_yoink("arm_optimized_routines_notice");
|
|
|
|
/*
|
|
LOG2F_TABLE_BITS = 4
|
|
LOG2F_POLY_ORDER = 4
|
|
|
|
ULP error: 0.752 (nearest rounding.)
|
|
Relative error: 1.9 * 2^-26 (before rounding.)
|
|
*/
|
|
|
|
#define N (1 << LOG2F_TABLE_BITS)
|
|
#define T __log2f_data.tab
|
|
#define A __log2f_data.poly
|
|
#define OFF 0x3f330000
|
|
|
|
/**
|
|
* Returns base-2 logarithm of x.
|
|
*
|
|
* - ULP error: 0.752 (nearest rounding.)
|
|
* - Relative error: 1.9 * 2^-26 (before rounding.)
|
|
*/
|
|
float
|
|
log2f (float x)
|
|
{
|
|
/* double_t for better performance on targets with FLT_EVAL_METHOD==2. */
|
|
double_t z, r, r2, p, y, y0, invc, logc;
|
|
uint32_t ix, iz, top, tmp;
|
|
int k, i;
|
|
|
|
ix = asuint (x);
|
|
#if WANT_ROUNDING
|
|
/* Fix sign of zero with downward rounding when x==1. */
|
|
if (unlikely (ix == 0x3f800000))
|
|
return 0;
|
|
#endif
|
|
if (unlikely (ix - 0x00800000 >= 0x7f800000 - 0x00800000))
|
|
{
|
|
/* x < 0x1p-126 or inf or nan. */
|
|
if (ix * 2 == 0)
|
|
return __math_divzerof (1);
|
|
if (ix == 0x7f800000) /* log2(inf) == inf. */
|
|
return x;
|
|
if ((ix & 0x80000000) || ix * 2 >= 0xff000000)
|
|
return __math_invalidf (x);
|
|
/* x is subnormal, normalize it. */
|
|
ix = asuint (x * 0x1p23f);
|
|
ix -= 23 << 23;
|
|
}
|
|
|
|
/* x = 2^k z; where z is in range [OFF,2*OFF] and exact.
|
|
The range is split into N subintervals.
|
|
The ith subinterval contains z and c is near its center. */
|
|
tmp = ix - OFF;
|
|
i = (tmp >> (23 - LOG2F_TABLE_BITS)) % N;
|
|
top = tmp & 0xff800000;
|
|
iz = ix - top;
|
|
k = (int32_t) tmp >> 23; /* arithmetic shift */
|
|
invc = T[i].invc;
|
|
logc = T[i].logc;
|
|
z = (double_t) asfloat (iz);
|
|
|
|
/* log2(x) = log1p(z/c-1)/ln2 + log2(c) + k */
|
|
r = z * invc - 1;
|
|
y0 = logc + (double_t) k;
|
|
|
|
/* Pipelined polynomial evaluation to approximate log1p(r)/ln2. */
|
|
r2 = r * r;
|
|
y = A[1] * r + A[2];
|
|
y = A[0] * r2 + y;
|
|
p = A[3] * r + y0;
|
|
y = y * r2 + p;
|
|
return eval_as_float (y);
|
|
}
|
|
|
|
#if USE_GLIBC_ABI
|
|
strong_alias (log2f, __log2f_finite)
|
|
hidden_alias (log2f, __ieee754_log2f)
|
|
#endif
|