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/* Single-precision vector (SVE) tanh 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/>. */
#include "sv_expm1f_inline.h"
static const struct data
{
struct sv_expm1f_data expm1f_consts;
uint32_t boring_bound, onef;
} data = {
.expm1f_consts = SV_EXPM1F_DATA,
/* 0x1.205966p+3, above which tanhf rounds to 1 (or -1 for negative). */
.boring_bound = 0x41102cb3,
.onef = 0x3f800000,
};
static svfloat32_t NOINLINE
special_case (svfloat32_t x, svfloat32_t y, svbool_t special)
{
return sv_call_f32 (tanhf, x, y, special);
}
/* Approximation for single-precision SVE tanh(x), using a simplified
version of expm1f. The maximum error is 2.57 ULP:
_ZGVsMxv_tanhf (0x1.fc1832p-5) got 0x1.fb71a4p-5
want 0x1.fb71aap-5. */
svfloat32_t SV_NAME_F1 (tanh) (svfloat32_t x, const svbool_t pg)
{
const struct data *d = ptr_barrier (&data);
svfloat32_t ax = svabs_x (pg, x);
svuint32_t iax = svreinterpret_u32 (ax);
svuint32_t sign = sveor_x (pg, svreinterpret_u32 (x), iax);
svbool_t is_boring = svcmpgt (pg, iax, d->boring_bound);
svfloat32_t boring = svreinterpret_f32 (svorr_x (pg, sign, d->onef));
svbool_t special = svcmpgt (pg, iax, 0x7f800000);
/* tanh(x) = (e^2x - 1) / (e^2x + 1). */
svfloat32_t q = expm1f_inline (svmul_x (pg, x, 2.0), pg, &d->expm1f_consts);
svfloat32_t y = svdiv_x (pg, q, svadd_x (pg, q, 2.0));
if (__glibc_unlikely (svptest_any (pg, special)))
return special_case (x, svsel_f32 (is_boring, boring, y), special);
return svsel_f32 (is_boring, boring, y);
}
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