Fixed glibc compatibility

This commit is contained in:
Alexey Milovidov 2019-08-01 06:20:54 +03:00
parent 027a39ff75
commit 99b9d354f7
5 changed files with 160 additions and 0 deletions

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#include <stdint.h>
/* fp_barrier returns its input, but limits code transformations
as if it had a side-effect (e.g. observable io) and returned
an arbitrary value. */
static inline float fp_barrierf(float x)
{
volatile float y = x;
return y;
}
float __math_divzerof(uint32_t sign)
{
return fp_barrierf(sign ? -1.0f : 1.0f) / 0.0f;
}

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float __math_invalidf(float x)
{
return (x - x) / (x - x);
}

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/*
* Single-precision log function.
*
* Copyright (c) 2017-2018, Arm Limited.
* SPDX-License-Identifier: MIT
*/
#include <math.h>
#include <stdint.h>
#include "logf_data.h"
float __math_invalidf(float);
float __math_divzerof(uint32_t);
/*
LOGF_TABLE_BITS = 4
LOGF_POLY_ORDER = 4
ULP error: 0.818 (nearest rounding.)
Relative error: 1.957 * 2^-26 (before rounding.)
*/
#define T __logf_data.tab
#define A __logf_data.poly
#define Ln2 __logf_data.ln2
#define N (1 << LOGF_TABLE_BITS)
#define OFF 0x3f330000
#define WANT_ROUNDING 1
#define asuint(f) ((union{float _f; uint32_t _i;}){f})._i
#define asfloat(i) ((union{uint32_t _i; float _f;}){i})._f
/* Evaluate an expression as the specified type. With standard excess
precision handling a type cast or assignment is enough (with
-ffloat-store an assignment is required, in old compilers argument
passing and return statement may not drop excess precision). */
static inline float eval_as_float(float x)
{
float y = x;
return y;
}
float logf(float x)
{
double_t z, r, r2, y, y0, invc, logc;
uint32_t ix, iz, tmp;
int k, i;
ix = asuint(x);
/* Fix sign of zero with downward rounding when x==1. */
if (WANT_ROUNDING && __builtin_expect(ix == 0x3f800000, 0))
return 0;
if (__builtin_expect(ix - 0x00800000 >= 0x7f800000 - 0x00800000, 0)) {
/* x < 0x1p-126 or inf or nan. */
if (ix * 2 == 0)
return __math_divzerof(1);
if (ix == 0x7f800000) /* log(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 - LOGF_TABLE_BITS)) % N;
k = (int32_t)tmp >> 23; /* arithmetic shift */
iz = ix - (tmp & 0x1ff << 23);
invc = T[i].invc;
logc = T[i].logc;
z = (double_t)asfloat(iz);
/* log(x) = log1p(z/c-1) + log(c) + k*Ln2 */
r = z * invc - 1;
y0 = logc + (double_t)k * Ln2;
/* Pipelined polynomial evaluation to approximate log1p(r). */
r2 = r * r;
y = A[1] * r + A[2];
y = A[0] * r2 + y;
y = y * r2 + (y0 + r);
return eval_as_float(y);
}

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/*
* Data definition for logf.
*
* Copyright (c) 2017-2018, Arm Limited.
* SPDX-License-Identifier: MIT
*/
#include "logf_data.h"
const struct logf_data __logf_data = {
.tab = {
{ 0x1.661ec79f8f3bep+0, -0x1.57bf7808caadep-2 },
{ 0x1.571ed4aaf883dp+0, -0x1.2bef0a7c06ddbp-2 },
{ 0x1.49539f0f010bp+0, -0x1.01eae7f513a67p-2 },
{ 0x1.3c995b0b80385p+0, -0x1.b31d8a68224e9p-3 },
{ 0x1.30d190c8864a5p+0, -0x1.6574f0ac07758p-3 },
{ 0x1.25e227b0b8eap+0, -0x1.1aa2bc79c81p-3 },
{ 0x1.1bb4a4a1a343fp+0, -0x1.a4e76ce8c0e5ep-4 },
{ 0x1.12358f08ae5bap+0, -0x1.1973c5a611cccp-4 },
{ 0x1.0953f419900a7p+0, -0x1.252f438e10c1ep-5 },
{ 0x1p+0, 0x0p+0 },
{ 0x1.e608cfd9a47acp-1, 0x1.aa5aa5df25984p-5 },
{ 0x1.ca4b31f026aap-1, 0x1.c5e53aa362eb4p-4 },
{ 0x1.b2036576afce6p-1, 0x1.526e57720db08p-3 },
{ 0x1.9c2d163a1aa2dp-1, 0x1.bc2860d22477p-3 },
{ 0x1.886e6037841edp-1, 0x1.1058bc8a07ee1p-2 },
{ 0x1.767dcf5534862p-1, 0x1.4043057b6ee09p-2 },
},
.ln2 = 0x1.62e42fefa39efp-1,
.poly = {
-0x1.00ea348b88334p-2, 0x1.5575b0be00b6ap-2, -0x1.ffffef20a4123p-2,
}
};

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/*
* Copyright (c) 2017-2018, Arm Limited.
* SPDX-License-Identifier: MIT
*/
#ifndef _LOGF_DATA_H
#define _LOGF_DATA_H
#define LOGF_TABLE_BITS 4
#define LOGF_POLY_ORDER 4
extern __attribute__((__visibility__("hidden"))) const struct logf_data {
struct {
double invc, logc;
} tab[1 << LOGF_TABLE_BITS];
double ln2;
double poly[LOGF_POLY_ORDER - 1]; /* First order coefficient is 1. */
} __logf_data;
#endif