mirror of git://sourceware.org/git/glibc.git
62 lines
2.1 KiB
C
62 lines
2.1 KiB
C
/* Single-precision (SVE) cospi 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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#include "poly_sve_f32.h"
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static const struct data
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{
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float poly[6];
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float range_val;
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} data = {
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/* Taylor series coefficents for sin(pi * x). */
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.poly = { 0x1.921fb6p1f, -0x1.4abbcep2f, 0x1.466bc6p1f, -0x1.32d2ccp-1f,
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0x1.50783p-4f, -0x1.e30750p-8f },
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.range_val = 0x1p31f,
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};
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/* A fast SVE implementation of cospif.
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Maximum error: 2.60 ULP:
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_ZGVsMxv_cospif(+/-0x1.cae664p-4) got 0x1.e09c9ep-1
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want 0x1.e09c98p-1. */
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svfloat32_t SV_NAME_F1 (cospi) (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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/* Using cospi(x) = sinpi(0.5 - x)
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range reduction and offset into sinpi range -1/2 .. 1/2
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r = 0.5 - |x - rint(x)|. */
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svfloat32_t n = svrinta_x (pg, x);
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svfloat32_t r = svsub_x (pg, x, n);
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r = svsub_x (pg, sv_f32 (0.5f), svabs_x (pg, r));
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/* Result should be negated based on if n is odd or not.
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If ax >= 2^31, the result will always be positive. */
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svbool_t cmp = svaclt (pg, x, d->range_val);
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svuint32_t intn = svreinterpret_u32 (svcvt_s32_x (pg, n));
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svuint32_t sign = svlsl_z (cmp, intn, 31);
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/* y = sin(r). */
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svfloat32_t r2 = svmul_x (pg, r, r);
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svfloat32_t y = sv_horner_5_f32_x (pg, r2, d->poly);
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y = svmul_x (pg, y, r);
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return svreinterpret_f32 (sveor_x (pg, svreinterpret_u32 (y), sign));
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}
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