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77 lines
2.5 KiB
C
77 lines
2.5 KiB
C
/* Helper for single-precision SVE routines which depend on log1p
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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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#ifndef AARCH64_FPU_SV_LOG1PF_INLINE_H
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#define AARCH64_FPU_SV_LOG1PF_INLINE_H
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#include "sv_math.h"
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#include "vecmath_config.h"
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#include "poly_sve_f32.h"
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static const struct sv_log1pf_data
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{
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float32_t poly[9];
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float32_t ln2;
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float32_t scale_back;
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} sv_log1pf_data = {
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/* Polynomial generated using FPMinimax in [-0.25, 0.5]. */
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.poly = { -0x1p-1f, 0x1.5555aap-2f, -0x1.000038p-2f, 0x1.99675cp-3f,
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-0x1.54ef78p-3f, 0x1.28a1f4p-3f, -0x1.0da91p-3f, 0x1.abcb6p-4f,
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-0x1.6f0d5ep-5f },
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.scale_back = 0x1.0p-23f,
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.ln2 = 0x1.62e43p-1f,
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};
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static inline svfloat32_t
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eval_poly (svfloat32_t m, const float32_t *c, svbool_t pg)
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{
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svfloat32_t p_12 = svmla_x (pg, sv_f32 (c[0]), m, sv_f32 (c[1]));
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svfloat32_t m2 = svmul_x (pg, m, m);
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svfloat32_t q = svmla_x (pg, m, m2, p_12);
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svfloat32_t p = sv_pw_horner_6_f32_x (pg, m, m2, c + 2);
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p = svmul_x (pg, m2, p);
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return svmla_x (pg, q, m2, p);
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}
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static inline svfloat32_t
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sv_log1pf_inline (svfloat32_t x, svbool_t pg)
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{
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const struct sv_log1pf_data *d = ptr_barrier (&sv_log1pf_data);
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svfloat32_t m = svadd_x (pg, x, 1.0f);
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svint32_t ks = svsub_x (pg, svreinterpret_s32 (m),
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svreinterpret_s32 (svdup_f32 (0.75f)));
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ks = svand_x (pg, ks, 0xff800000);
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svuint32_t k = svreinterpret_u32 (ks);
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svfloat32_t s = svreinterpret_f32 (
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svsub_x (pg, svreinterpret_u32 (svdup_f32 (4.0f)), k));
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svfloat32_t m_scale
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= svreinterpret_f32 (svsub_x (pg, svreinterpret_u32 (x), k));
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m_scale
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= svadd_x (pg, m_scale, svmla_x (pg, sv_f32 (-1.0f), sv_f32 (0.25f), s));
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svfloat32_t p = eval_poly (m_scale, d->poly, pg);
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svfloat32_t scale_back = svmul_x (pg, svcvt_f32_x (pg, k), d->scale_back);
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return svmla_x (pg, p, scale_back, d->ln2);
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}
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#endif
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