diff options
Diffstat (limited to 'sysdeps/aarch64/fpu/sinh_sve.c')
| -rw-r--r-- | sysdeps/aarch64/fpu/sinh_sve.c | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/sysdeps/aarch64/fpu/sinh_sve.c b/sysdeps/aarch64/fpu/sinh_sve.c new file mode 100644 index 0000000000..df5f6c8c06 --- /dev/null +++ b/sysdeps/aarch64/fpu/sinh_sve.c @@ -0,0 +1,107 @@ +/* Double-precision vector (SVE) atanh function + + Copyright (C) 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 "sv_math.h" +#include "poly_sve_f64.h" + +static const struct data +{ + float64_t poly[11]; + float64_t inv_ln2, m_ln2_hi, m_ln2_lo, shift; + uint64_t halff; + int64_t onef; + uint64_t large_bound; +} data = { + /* Generated using Remez, deg=12 in [-log(2)/2, log(2)/2]. */ + .poly = { 0x1p-1, 0x1.5555555555559p-3, 0x1.555555555554bp-5, + 0x1.111111110f663p-7, 0x1.6c16c16c1b5f3p-10, + 0x1.a01a01affa35dp-13, 0x1.a01a018b4ecbbp-16, + 0x1.71ddf82db5bb4p-19, 0x1.27e517fc0d54bp-22, + 0x1.af5eedae67435p-26, 0x1.1f143d060a28ap-29, }, + + .inv_ln2 = 0x1.71547652b82fep0, + .m_ln2_hi = -0x1.62e42fefa39efp-1, + .m_ln2_lo = -0x1.abc9e3b39803fp-56, + .shift = 0x1.8p52, + + .halff = 0x3fe0000000000000, + .onef = 0x3ff0000000000000, + /* 2^9. expm1 helper overflows for large input. */ + .large_bound = 0x4080000000000000, +}; + +static inline svfloat64_t +expm1_inline (svfloat64_t x, svbool_t pg) +{ + const struct data *d = ptr_barrier (&data); + + /* Reduce argument: + exp(x) - 1 = 2^i * (expm1(f) + 1) - 1 + where i = round(x / ln2) + and f = x - i * ln2 (f in [-ln2/2, ln2/2]). */ + svfloat64_t j + = svsub_x (pg, svmla_x (pg, sv_f64 (d->shift), x, d->inv_ln2), d->shift); + svint64_t i = svcvt_s64_x (pg, j); + svfloat64_t f = svmla_x (pg, x, j, d->m_ln2_hi); + f = svmla_x (pg, f, j, d->m_ln2_lo); + /* Approximate expm1(f) using polynomial. */ + svfloat64_t f2 = svmul_x (pg, f, f); + svfloat64_t f4 = svmul_x (pg, f2, f2); + svfloat64_t f8 = svmul_x (pg, f4, f4); + svfloat64_t p + = svmla_x (pg, f, f2, sv_estrin_10_f64_x (pg, f, f2, f4, f8, d->poly)); + /* t = 2^i. */ + svfloat64_t t = svscale_x (pg, sv_f64 (1), i); + /* expm1(x) ~= p * t + (t - 1). */ + return svmla_x (pg, svsub_x (pg, t, 1.0), p, t); +} + +static svfloat64_t NOINLINE +special_case (svfloat64_t x, svbool_t pg) +{ + return sv_call_f64 (sinh, x, x, pg); +} + +/* Approximation for SVE double-precision sinh(x) using expm1. + sinh(x) = (exp(x) - exp(-x)) / 2. + The greatest observed error is 2.57 ULP: + _ZGVsMxv_sinh (0x1.a008538399931p-2) got 0x1.ab929fc64bd66p-2 + want 0x1.ab929fc64bd63p-2. */ +svfloat64_t SV_NAME_D1 (sinh) (svfloat64_t x, svbool_t pg) +{ + const struct data *d = ptr_barrier (&data); + + svfloat64_t ax = svabs_x (pg, x); + svuint64_t sign + = sveor_x (pg, svreinterpret_u64 (x), svreinterpret_u64 (ax)); + svfloat64_t halfsign = svreinterpret_f64 (svorr_x (pg, sign, d->halff)); + + svbool_t special = svcmpge (pg, svreinterpret_u64 (ax), d->large_bound); + + /* Fall back to scalar variant for all lanes if any are special. */ + if (__glibc_unlikely (svptest_any (pg, special))) + return special_case (x, pg); + + /* Up to the point that expm1 overflows, we can use it to calculate sinh + using a slight rearrangement of the definition of sinh. This allows us to + retain acceptable accuracy for very small inputs. */ + svfloat64_t t = expm1_inline (ax, pg); + t = svadd_x (pg, t, svdiv_x (pg, t, svadd_x (pg, t, 1.0))); + return svmul_x (pg, t, halfsign); +} |