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