1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
/* Single-precision inline helper for vector (Advanced SIMD) expm1 function
Copyright (C) 2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef AARCH64_FPU_V_EXPM1F_INLINE_H
#define AARCH64_FPU_V_EXPM1F_INLINE_H
#include "v_math.h"
#include "poly_advsimd_f32.h"
struct v_expm1f_data
{
float32x4_t poly[5];
float32x4_t invln2_and_ln2, shift;
int32x4_t exponent_bias;
};
/* Coefficients generated using fpminimax with degree=5 in [-log(2)/2,
log(2)/2]. Exponent bias is asuint(1.0f).
invln2_and_ln2 Stores constants: invln2, ln2_lo, ln2_hi, 0. */
#define V_EXPM1F_DATA \
{ \
.poly = { V4 (0x1.fffffep-2), V4 (0x1.5554aep-3), V4 (0x1.555736p-5), \
V4 (0x1.12287cp-7), V4 (0x1.6b55a2p-10) }, \
.shift = V4 (0x1.8p23f), .exponent_bias = V4 (0x3f800000), \
.invln2_and_ln2 = { 0x1.715476p+0f, 0x1.62e4p-1f, 0x1.7f7d1cp-20f, 0 }, \
}
static inline float32x4_t
expm1f_inline (float32x4_t x, const struct v_expm1f_data *d)
{
/* Helper routine for calculating exp(x) - 1.
Copied from v_expm1f_1u6.c, with all special-case handling removed - the
calling routine should handle special values if required. */
/* Reduce argument: f in [-ln2/2, ln2/2], i is exact. */
float32x4_t j = vsubq_f32 (
vfmaq_laneq_f32 (d->shift, x, d->invln2_and_ln2, 0), d->shift);
int32x4_t i = vcvtq_s32_f32 (j);
float32x4_t f = vfmsq_laneq_f32 (x, j, d->invln2_and_ln2, 1);
f = vfmsq_laneq_f32 (f, j, d->invln2_and_ln2, 2);
/* Approximate expm1(f) with polynomial P, expm1(f) ~= f + f^2 * P(f).
Uses Estrin scheme, where the main _ZGVnN4v_expm1f routine uses
Horner. */
float32x4_t f2 = vmulq_f32 (f, f);
float32x4_t f4 = vmulq_f32 (f2, f2);
float32x4_t p = v_estrin_4_f32 (f, f2, f4, d->poly);
p = vfmaq_f32 (f, f2, p);
/* t = 2^i. */
int32x4_t u = vaddq_s32 (vshlq_n_s32 (i, 23), d->exponent_bias);
float32x4_t t = vreinterpretq_f32_s32 (u);
/* expm1(x) ~= p * t + (t - 1). */
return vfmaq_f32 (vsubq_f32 (t, v_f32 (1.0f)), p, t);
}
#endif
|
