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62 lines
2.2 KiB
C
62 lines
2.2 KiB
C
/* Single-precision vector (SVE) tanh function
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Copyright (C) 2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include "sv_expm1f_inline.h"
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static const struct data
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{
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struct sv_expm1f_data expm1f_consts;
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uint32_t boring_bound, onef;
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} data = {
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.expm1f_consts = SV_EXPM1F_DATA,
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/* 0x1.205966p+3, above which tanhf rounds to 1 (or -1 for negative). */
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.boring_bound = 0x41102cb3,
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.onef = 0x3f800000,
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};
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static svfloat32_t NOINLINE
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special_case (svfloat32_t x, svfloat32_t y, svbool_t special)
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{
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return sv_call_f32 (tanhf, x, y, special);
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}
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/* Approximation for single-precision SVE tanh(x), using a simplified
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version of expm1f. The maximum error is 2.57 ULP:
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_ZGVsMxv_tanhf (0x1.fc1832p-5) got 0x1.fb71a4p-5
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want 0x1.fb71aap-5. */
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svfloat32_t SV_NAME_F1 (tanh) (svfloat32_t x, const svbool_t pg)
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{
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const struct data *d = ptr_barrier (&data);
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svfloat32_t ax = svabs_x (pg, x);
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svuint32_t iax = svreinterpret_u32 (ax);
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svuint32_t sign = sveor_x (pg, svreinterpret_u32 (x), iax);
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svbool_t is_boring = svcmpgt (pg, iax, d->boring_bound);
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svfloat32_t boring = svreinterpret_f32 (svorr_x (pg, sign, d->onef));
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svbool_t special = svcmpgt (pg, iax, 0x7f800000);
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/* tanh(x) = (e^2x - 1) / (e^2x + 1). */
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svfloat32_t q = expm1f_inline (svmul_x (pg, x, 2.0), pg, &d->expm1f_consts);
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svfloat32_t y = svdiv_x (pg, q, svadd_x (pg, q, 2.0));
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if (__glibc_unlikely (svptest_any (pg, special)))
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return special_case (x, svsel_f32 (is_boring, boring, y), special);
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return svsel_f32 (is_boring, boring, y);
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}
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