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7900ac490d
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. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
84 lines
2.8 KiB
C
84 lines
2.8 KiB
C
/* Single-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_expm1f_inline.h"
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static const struct data
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{
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struct v_expm1f_data d;
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#if WANT_SIMD_EXCEPT
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uint32x4_t thresh;
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#else
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float32x4_t oflow_bound;
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#endif
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} data = {
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.d = V_EXPM1F_DATA,
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#if !WANT_SIMD_EXCEPT
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/* Value above which expm1f(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 = V4 (0x1.5ebc4p+6),
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#else
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/* asuint(oflow_bound) - asuint(0x1p-23), shifted left by 1 for absolute
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compare. */
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.thresh = V4 (0x1d5ebc40),
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#endif
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};
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/* asuint(0x1p-23), shifted by 1 for abs compare. */
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#define TinyBound v_u32 (0x34000000 << 1)
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static float32x4_t VPCS_ATTR NOINLINE
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special_case (float32x4_t x, uint32x4_t special, const struct data *d)
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{
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return v_call_f32 (
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expm1f, x, expm1f_inline (v_zerofy_f32 (x, special), &d->d), special);
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}
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/* Single-precision vector exp(x) - 1 function.
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The maximum error is 1.62 ULP:
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_ZGVnN4v_expm1f(0x1.85f83p-2) got 0x1.da9f4p-2
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want 0x1.da9f44p-2. */
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float32x4_t VPCS_ATTR NOINLINE V_NAME_F1 (expm1) (float32x4_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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uint32x4_t ix = vreinterpretq_u32_f32 (x);
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/* If fp exceptions are to be triggered correctly, fall back to scalar for
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|x| < 2^-23, |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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uint32x4_t special
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= vcgeq_u32 (vsubq_u32 (vaddq_u32 (ix, ix), TinyBound), d->thresh);
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#else
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/* Handles very large values (+ve and -ve), +/-NaN, +/-Inf. */
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uint32x4_t special = vcagtq_f32 (x, d->oflow_bound);
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#endif
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if (__glibc_unlikely (v_any_u32 (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 expm1f_inline (x, &d->d);
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}
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libmvec_hidden_def (V_NAME_F1 (expm1))
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HALF_WIDTH_ALIAS_F1 (expm1)
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