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99 lines
3.3 KiB
C
99 lines
3.3 KiB
C
/* Single-precision vector (SVE) sin function.
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Copyright (C) 2023-2024 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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static const struct data
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{
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float poly[4];
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/* Pi-related values to be loaded as one quad-word and used with
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svmla_lane. */
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float negpi1, negpi2, negpi3, invpi;
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float shift;
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} data = {
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.poly = {
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/* Non-zero coefficients from the degree 9 Taylor series expansion of
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sin. */
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-0x1.555548p-3f, 0x1.110df4p-7f, -0x1.9f42eap-13f, 0x1.5b2e76p-19f
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},
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.negpi1 = -0x1.921fb6p+1f,
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.negpi2 = 0x1.777a5cp-24f,
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.negpi3 = 0x1.ee59dap-49f,
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.invpi = 0x1.45f306p-2f,
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.shift = 0x1.8p+23f
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};
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#define RangeVal 0x49800000 /* asuint32 (0x1p20f). */
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#define C(i) sv_f32 (d->poly[i])
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static svfloat32_t NOINLINE
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special_case (svfloat32_t x, svfloat32_t y, svbool_t cmp)
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{
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return sv_call_f32 (sinf, x, y, cmp);
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}
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/* A fast SVE implementation of sinf.
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Maximum error: 1.89 ULPs.
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This maximum error is achieved at multiple values in [-2^18, 2^18]
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but one example is:
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SV_NAME_F1 (sin)(0x1.9247a4p+0) got 0x1.fffff6p-1 want 0x1.fffffap-1. */
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svfloat32_t SV_NAME_F1 (sin) (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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svfloat32_t ax = svabs_x (pg, x);
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svuint32_t sign
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= sveor_x (pg, svreinterpret_u32 (x), svreinterpret_u32 (ax));
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svbool_t cmp = svcmpge (pg, svreinterpret_u32 (ax), RangeVal);
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/* pi_vals are a quad-word of helper values - the first 3 elements contain
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-pi in extended precision, the last contains 1 / pi. */
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svfloat32_t pi_vals = svld1rq (svptrue_b32 (), &d->negpi1);
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/* n = rint(|x|/pi). */
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svfloat32_t n = svmla_lane (sv_f32 (d->shift), ax, pi_vals, 3);
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svuint32_t odd = svlsl_x (pg, svreinterpret_u32 (n), 31);
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n = svsub_x (pg, n, d->shift);
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/* r = |x| - n*pi (range reduction into -pi/2 .. pi/2). */
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svfloat32_t r;
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r = svmla_lane (ax, n, pi_vals, 0);
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r = svmla_lane (r, n, pi_vals, 1);
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r = svmla_lane (r, n, pi_vals, 2);
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/* sin(r) approx using a degree 9 polynomial from the Taylor series
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expansion. Note that only the odd terms of this are non-zero. */
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svfloat32_t r2 = svmul_x (pg, r, r);
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svfloat32_t y;
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y = svmla_x (pg, C (2), r2, C (3));
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y = svmla_x (pg, C (1), r2, y);
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y = svmla_x (pg, C (0), r2, y);
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y = svmla_x (pg, r, r, svmul_x (pg, y, r2));
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/* sign = y^sign^odd. */
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sign = sveor_x (pg, sign, odd);
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if (__glibc_unlikely (svptest_any (pg, cmp)))
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return special_case (x,
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svreinterpret_f32 (sveor_x (
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svnot_z (pg, cmp), svreinterpret_u32 (y), sign)),
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cmp);
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return svreinterpret_f32 (sveor_x (pg, svreinterpret_u32 (y), sign));
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}
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