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52 lines
2.0 KiB
C
52 lines
2.0 KiB
C
/* Double-precision vector (SVE) acosh 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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#define WANT_SV_LOG1P_K0_SHORTCUT 1
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#include "sv_log1p_inline.h"
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#define One (0x3ff0000000000000)
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#define Thres (0x1ff0000000000000) /* asuint64 (0x1p511) - One. */
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static svfloat64_t NOINLINE
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special_case (svfloat64_t x, svfloat64_t y, svbool_t special)
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{
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return sv_call_f64 (acosh, x, y, special);
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}
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/* SVE approximation for double-precision acosh, based on log1p.
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The largest observed error is 3.19 ULP in the region where the
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argument to log1p falls in the k=0 interval, i.e. x close to 1:
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SV_NAME_D1 (acosh)(0x1.1e4388d4ca821p+0) got 0x1.ed23399f5137p-2
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want 0x1.ed23399f51373p-2. */
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svfloat64_t SV_NAME_D1 (acosh) (svfloat64_t x, const svbool_t pg)
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{
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/* (ix - One) >= (BigBound - One). */
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svuint64_t ix = svreinterpret_u64 (x);
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svbool_t special = svcmpge (pg, svsub_x (pg, ix, One), Thres);
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svfloat64_t xm1 = svsub_x (pg, x, 1.0);
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svfloat64_t u = svmul_x (pg, xm1, svadd_x (pg, x, 1.0));
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svfloat64_t y = svadd_x (pg, xm1, svsqrt_x (pg, u));
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/* Fall back to scalar routine for special lanes. */
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if (__glibc_unlikely (svptest_any (pg, special)))
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return special_case (x, sv_log1p_inline (y, pg), special);
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return sv_log1p_inline (y, pg);
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}
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