mirror of git://sourceware.org/git/glibc.git
89 lines
3.4 KiB
C
89 lines
3.4 KiB
C
/* Double-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_tanpi_data
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{
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double c0, c2, c4, c6, c8, c10, c12;
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double c1, c3, c5, c7, c9, c11, c13, c14;
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} tanpi_data = {
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/* Coefficents for tan(pi * x) computed with fpminimax
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on [ 0x1p-1022 0x1p-2 ]
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approx rel error: 0x1.7eap-55
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approx abs error: 0x1.7eap-55. */
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.c0 = 0x1.921fb54442d18p1, /* pi. */
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.c1 = 0x1.4abbce625be52p3, .c2 = 0x1.466bc6775b0f9p5,
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.c3 = 0x1.45fff9b426f5ep7, .c4 = 0x1.45f4730dbca5cp9,
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.c5 = 0x1.45f3265994f85p11, .c6 = 0x1.45f4234b330cap13,
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.c7 = 0x1.45dca11be79ebp15, .c8 = 0x1.47283fc5eea69p17,
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.c9 = 0x1.3a6d958cdefaep19, .c10 = 0x1.927896baee627p21,
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.c11 = -0x1.89333f6acd922p19, .c12 = 0x1.5d4e912bb8456p27,
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.c13 = -0x1.a854d53ab6874p29, .c14 = 0x1.1b76de7681424p32,
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};
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/* Approximation for double-precision vector tanpi(x)
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The maximum error is 3.06 ULP:
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_ZGVsMxv_tanpi(0x1.0a4a07dfcca3ep-1) got -0x1.fa30112702c98p+3
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want -0x1.fa30112702c95p+3. */
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svfloat64_t SV_NAME_D1 (tanpi) (svfloat64_t x, const svbool_t pg)
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{
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const struct v_tanpi_data *d = ptr_barrier (&tanpi_data);
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svfloat64_t n = svrintn_x (pg, x);
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/* inf produces nan that propagates. */
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svfloat64_t xr = svsub_x (pg, x, n);
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svfloat64_t ar = svabd_x (pg, x, n);
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svbool_t flip = svcmpgt (pg, ar, 0.25);
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svfloat64_t r = svsel (flip, svsubr_x (pg, ar, 0.5), ar);
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/* Order-14 pairwise Horner. */
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svfloat64_t r2 = svmul_x (pg, r, r);
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svfloat64_t r4 = svmul_x (pg, r2, r2);
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svfloat64_t c_1_3 = svld1rq (pg, &d->c1);
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svfloat64_t c_5_7 = svld1rq (pg, &d->c5);
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svfloat64_t c_9_11 = svld1rq (pg, &d->c9);
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svfloat64_t c_13_14 = svld1rq (pg, &d->c13);
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svfloat64_t p01 = svmla_lane (sv_f64 (d->c0), r2, c_1_3, 0);
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svfloat64_t p23 = svmla_lane (sv_f64 (d->c2), r2, c_1_3, 1);
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svfloat64_t p45 = svmla_lane (sv_f64 (d->c4), r2, c_5_7, 0);
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svfloat64_t p67 = svmla_lane (sv_f64 (d->c6), r2, c_5_7, 1);
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svfloat64_t p89 = svmla_lane (sv_f64 (d->c8), r2, c_9_11, 0);
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svfloat64_t p1011 = svmla_lane (sv_f64 (d->c10), r2, c_9_11, 1);
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svfloat64_t p1213 = svmla_lane (sv_f64 (d->c12), r2, c_13_14, 0);
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svfloat64_t p = svmla_lane (p1213, r4, c_13_14, 1);
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p = svmad_x (pg, p, r4, p1011);
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p = svmad_x (pg, p, r4, p89);
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p = svmad_x (pg, p, r4, p67);
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p = svmad_x (pg, p, 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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p = svmul_x (pg, r, p);
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svfloat64_t p_recip = svdivr_x (pg, p, 1.0);
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svfloat64_t y = svsel (flip, p_recip, p);
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svuint64_t sign
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= sveor_x (pg, svreinterpret_u64 (xr), svreinterpret_u64 (ar));
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return svreinterpret_f64 (svorr_x (pg, svreinterpret_u64 (y), sign));
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}
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