diff options
Diffstat (limited to 'sysdeps/aarch64/fpu/log10f_advsimd.c')
| -rw-r--r-- | sysdeps/aarch64/fpu/log10f_advsimd.c | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/sysdeps/aarch64/fpu/log10f_advsimd.c b/sysdeps/aarch64/fpu/log10f_advsimd.c new file mode 100644 index 0000000000..ba02060bbe --- /dev/null +++ b/sysdeps/aarch64/fpu/log10f_advsimd.c @@ -0,0 +1,82 @@ +/* Single-precision vector (AdvSIMD) log10 function + + Copyright (C) 2023 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 "poly_advsimd_f32.h" + +static const struct data +{ + uint32x4_t min_norm; + uint16x8_t special_bound; + float32x4_t poly[8]; + float32x4_t inv_ln10, ln2; + uint32x4_t off, mantissa_mask; +} data = { + /* Use order 9 for log10(1+x), i.e. order 8 for log10(1+x)/x, with x in + [-1/3, 1/3] (offset=2/3). Max. relative error: 0x1.068ee468p-25. */ + .poly = { V4 (-0x1.bcb79cp-3f), V4 (0x1.2879c8p-3f), V4 (-0x1.bcd472p-4f), + V4 (0x1.6408f8p-4f), V4 (-0x1.246f8p-4f), V4 (0x1.f0e514p-5f), + V4 (-0x1.0fc92cp-4f), V4 (0x1.f5f76ap-5f) }, + .ln2 = V4 (0x1.62e43p-1f), + .inv_ln10 = V4 (0x1.bcb7b2p-2f), + .min_norm = V4 (0x00800000), + .special_bound = V8 (0x7f00), /* asuint32(inf) - min_norm. */ + .off = V4 (0x3f2aaaab), /* 0.666667. */ + .mantissa_mask = V4 (0x007fffff), +}; + +static float32x4_t VPCS_ATTR NOINLINE +special_case (float32x4_t x, float32x4_t y, float32x4_t p, float32x4_t r2, + uint16x4_t cmp) +{ + /* Fall back to scalar code. */ + return v_call_f32 (log10f, x, vfmaq_f32 (y, p, r2), vmovl_u16 (cmp)); +} + +/* Fast implementation of AdvSIMD log10f, + uses a similar approach as AdvSIMD logf with the same offset (i.e., 2/3) and + an order 9 polynomial. + Maximum error: 3.305ulps (nearest rounding.) + _ZGVnN4v_log10f(0x1.555c16p+0) got 0x1.ffe2fap-4 + want 0x1.ffe2f4p-4. */ +float32x4_t VPCS_ATTR V_NAME_F1 (log10) (float32x4_t x) +{ + const struct data *d = ptr_barrier (&data); + uint32x4_t u = vreinterpretq_u32_f32 (x); + uint16x4_t special = vcge_u16 (vsubhn_u32 (u, d->min_norm), + vget_low_u16 (d->special_bound)); + + /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ + u = vsubq_u32 (u, d->off); + float32x4_t n = vcvtq_f32_s32 ( + vshrq_n_s32 (vreinterpretq_s32_u32 (u), 23)); /* signextend. */ + u = vaddq_u32 (vandq_u32 (u, d->mantissa_mask), d->off); + float32x4_t r = vsubq_f32 (vreinterpretq_f32_u32 (u), v_f32 (1.0f)); + + /* y = log10(1+r) + n * log10(2). */ + float32x4_t r2 = vmulq_f32 (r, r); + float32x4_t poly = v_pw_horner_7_f32 (r, r2, d->poly); + /* y = Log10(2) * n + poly * InvLn(10). */ + float32x4_t y = vfmaq_f32 (r, d->ln2, n); + y = vmulq_f32 (y, d->inv_ln10); + + if (__glibc_unlikely (v_any_u16h (special))) + return special_case (x, y, poly, r2, special); + return vfmaq_f32 (y, poly, r2); +} |