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/* Single-precision AdvSIMD expm1
Copyright (C) 2023-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include "v_math.h"
#include "v_expm1f_inline.h"
static const struct data
{
struct v_expm1f_data d;
#if WANT_SIMD_EXCEPT
uint32x4_t thresh;
#else
float32x4_t oflow_bound;
#endif
} data = {
.d = V_EXPM1F_DATA,
#if !WANT_SIMD_EXCEPT
/* Value above which expm1f(x) should overflow. Absolute value of the
underflow bound is greater than this, so it catches both cases - there is
a small window where fallbacks are triggered unnecessarily. */
.oflow_bound = V4 (0x1.5ebc4p+6),
#else
/* asuint(oflow_bound) - asuint(0x1p-23), shifted left by 1 for absolute
compare. */
.thresh = V4 (0x1d5ebc40),
#endif
};
/* asuint(0x1p-23), shifted by 1 for abs compare. */
#define TinyBound v_u32 (0x34000000 << 1)
static float32x4_t VPCS_ATTR NOINLINE
special_case (float32x4_t x, uint32x4_t special, const struct data *d)
{
return v_call_f32 (
expm1f, x, expm1f_inline (v_zerofy_f32 (x, special), &d->d), special);
}
/* Single-precision vector exp(x) - 1 function.
The maximum error is 1.62 ULP:
_ZGVnN4v_expm1f(0x1.85f83p-2) got 0x1.da9f4p-2
want 0x1.da9f44p-2. */
float32x4_t VPCS_ATTR NOINLINE V_NAME_F1 (expm1) (float32x4_t x)
{
const struct data *d = ptr_barrier (&data);
#if WANT_SIMD_EXCEPT
uint32x4_t ix = vreinterpretq_u32_f32 (x);
/* If fp exceptions are to be triggered correctly, fall back to scalar for
|x| < 2^-23, |x| > oflow_bound, Inf & NaN. Add ix to itself for
shift-left by 1, and compare with thresh which was left-shifted offline -
this is effectively an absolute compare. */
uint32x4_t special
= vcgeq_u32 (vsubq_u32 (vaddq_u32 (ix, ix), TinyBound), d->thresh);
#else
/* Handles very large values (+ve and -ve), +/-NaN, +/-Inf. */
uint32x4_t special = vcagtq_f32 (x, d->oflow_bound);
#endif
if (__glibc_unlikely (v_any_u32 (special)))
return special_case (x, special, d);
/* expm1(x) ~= p * t + (t - 1). */
return expm1f_inline (x, &d->d);
}
libmvec_hidden_def (V_NAME_F1 (expm1))
HALF_WIDTH_ALIAS_F1 (expm1)
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