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/* Single-precision (SVE) tanpi 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_math.h"
const static struct v_tanpif_data
{
float c0, c2, c4, c6;
float c1, c3, c5, c7;
} tanpif_data = {
/* Coefficients for tan(pi * x). */
.c0 = 0x1.921fb4p1f, .c1 = 0x1.4abbcep3f, .c2 = 0x1.466b8p5f,
.c3 = 0x1.461c72p7f, .c4 = 0x1.42e9d4p9f, .c5 = 0x1.69e2c4p11f,
.c6 = 0x1.e85558p11f, .c7 = 0x1.a52e08p16f,
};
/* Approximation for single-precision vector tanpif(x)
The maximum error is 3.34 ULP:
_ZGVsMxv_tanpif(0x1.d6c09ap-2) got 0x1.f70aacp+2
want 0x1.f70aa6p+2. */
svfloat32_t SV_NAME_F1 (tanpi) (svfloat32_t x, const svbool_t pg)
{
const struct v_tanpif_data *d = ptr_barrier (&tanpif_data);
svfloat32_t odd_coeffs = svld1rq (pg, &d->c1);
svfloat32_t n = svrintn_x (pg, x);
/* inf produces nan that propagates. */
svfloat32_t xr = svsub_x (pg, x, n);
svfloat32_t ar = svabd_x (pg, x, n);
svbool_t flip = svcmpgt (pg, ar, 0.25f);
svfloat32_t r = svsel (flip, svsub_x (pg, sv_f32 (0.5f), ar), ar);
svfloat32_t r2 = svmul_x (pg, r, r);
svfloat32_t r4 = svmul_x (pg, r2, r2);
/* Order-7 Pairwise Horner. */
svfloat32_t p01 = svmla_lane (sv_f32 (d->c0), r2, odd_coeffs, 0);
svfloat32_t p23 = svmla_lane (sv_f32 (d->c2), r2, odd_coeffs, 1);
svfloat32_t p45 = svmla_lane (sv_f32 (d->c4), r2, odd_coeffs, 2);
svfloat32_t p67 = svmla_lane (sv_f32 (d->c6), r2, odd_coeffs, 3);
svfloat32_t p = svmad_x (pg, p67, r4, p45);
p = svmad_x (pg, p, r4, p23);
p = svmad_x (pg, p, r4, p01);
svfloat32_t poly = svmul_x (pg, r, p);
svfloat32_t poly_recip = svdiv_x (pg, sv_f32 (1.0), poly);
svfloat32_t y = svsel (flip, poly_recip, poly);
svuint32_t sign
= sveor_x (pg, svreinterpret_u32 (xr), svreinterpret_u32 (ar));
return svreinterpret_f32 (svorr_x (pg, svreinterpret_u32 (y), sign));
}
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