mirror of git://sourceware.org/git/glibc.git
65 lines
2.2 KiB
C
65 lines
2.2 KiB
C
/* SVE helper for single-precision routines which depend on exp
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Copyright (C) 2024-2025 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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#ifndef AARCH64_FPU_SV_EXPF_INLINE_H
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#define AARCH64_FPU_SV_EXPF_INLINE_H
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#include "sv_math.h"
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struct sv_expf_data
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{
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float ln2_hi, ln2_lo, c1, null;
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float inv_ln2, shift;
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};
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/* Shift is 1.5*2^17 + 127. */
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#define SV_EXPF_DATA \
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{ \
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.c1 = 0.5f, .inv_ln2 = 0x1.715476p+0f, .ln2_hi = 0x1.62e4p-1f, \
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.ln2_lo = 0x1.7f7d1cp-20f, .shift = 0x1.803f8p17f, \
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}
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static inline svfloat32_t
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expf_inline (svfloat32_t x, const svbool_t pg, const struct sv_expf_data *d)
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{
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/* exp(x) = 2^n (1 + poly(r)), with 1 + poly(r) in [1/sqrt(2),sqrt(2)]
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x = ln2*n + r, with r in [-ln2/2, ln2/2]. */
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svfloat32_t lane_consts = svld1rq (svptrue_b32 (), &d->ln2_hi);
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/* n = round(x/(ln2/N)). */
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svfloat32_t z = svmad_x (pg, sv_f32 (d->inv_ln2), x, d->shift);
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svfloat32_t n = svsub_x (pg, z, d->shift);
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/* r = x - n*ln2/N. */
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svfloat32_t r = x;
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r = svmls_lane (r, n, lane_consts, 0);
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r = svmls_lane (r, n, lane_consts, 1);
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/* scale = 2^(n/N). */
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svfloat32_t scale = svexpa (svreinterpret_u32 (z));
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/* poly(r) = exp(r) - 1 ~= r + 0.5 r^2. */
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svfloat32_t r2 = svmul_x (svptrue_b32 (), r, r);
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svfloat32_t poly = svmla_lane (r, r2, lane_consts, 2);
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return svmla_x (pg, scale, scale, poly);
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}
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#endif
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