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git://sourceware.org/git/glibc.git
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13a7ef5999
Add inline helper for expm1 and rearrange operations so MOV is not necessary in reduction or around the special-case handler. Reduce memory access by using more indexed MLAs in polynomial. Speedup on Neoverse V1 for expm1 (19%), sinh (8.5%), and tanh (7.5%).
81 lines
2.7 KiB
C
81 lines
2.7 KiB
C
/* Double-precision AdvSIMD expm1
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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 "v_math.h"
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#include "v_expm1_inline.h"
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static const struct data
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{
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struct v_expm1_data d;
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#if WANT_SIMD_EXCEPT
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uint64x2_t thresh, tiny_bound;
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#else
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float64x2_t oflow_bound;
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#endif
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} data = {
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.d = V_EXPM1_DATA,
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#if WANT_SIMD_EXCEPT
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/* asuint64(oflow_bound) - asuint64(0x1p-51), shifted left by 1 for abs
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compare. */
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.thresh = V2 (0x78c56fa6d34b552),
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/* asuint64(0x1p-51) << 1. */
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.tiny_bound = V2 (0x3cc0000000000000 << 1),
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#else
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/* Value above which expm1(x) should overflow. Absolute value of the
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underflow bound is greater than this, so it catches both cases - there is
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a small window where fallbacks are triggered unnecessarily. */
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.oflow_bound = V2 (0x1.62b7d369a5aa9p+9),
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#endif
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};
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static float64x2_t VPCS_ATTR NOINLINE
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special_case (float64x2_t x, uint64x2_t special, const struct data *d)
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{
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return v_call_f64 (expm1, x, expm1_inline (v_zerofy_f64 (x, special), &d->d),
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special);
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}
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/* Double-precision vector exp(x) - 1 function.
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The maximum error observed error is 2.05 ULP:
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_ZGVnN2v_expm1(0x1.634902eaff3adp-2) got 0x1.a8b636e2a9388p-2
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want 0x1.a8b636e2a9386p-2. */
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float64x2_t VPCS_ATTR V_NAME_D1 (expm1) (float64x2_t x)
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{
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const struct data *d = ptr_barrier (&data);
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#if WANT_SIMD_EXCEPT
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uint64x2_t ix = vreinterpretq_u64_f64 (x);
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/* If fp exceptions are to be triggered correctly, fall back to scalar for
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|x| < 2^-51, |x| > oflow_bound, Inf & NaN. Add ix to itself for
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shift-left by 1, and compare with thresh which was left-shifted offline -
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this is effectively an absolute compare. */
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uint64x2_t special
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= vcgeq_u64 (vsubq_u64 (vaddq_u64 (ix, ix), d->tiny_bound), d->thresh);
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#else
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/* Large input, NaNs and Infs. */
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uint64x2_t special = vcageq_f64 (x, d->oflow_bound);
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#endif
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if (__glibc_unlikely (v_any_u64 (special)))
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return special_case (x, special, d);
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/* expm1(x) ~= p * t + (t - 1). */
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return expm1_inline (x, &d->d);
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}
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