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Diffstat (limited to 'math/aarch64/sve/log10f.c')
| -rw-r--r-- | math/aarch64/sve/log10f.c | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/math/aarch64/sve/log10f.c b/math/aarch64/sve/log10f.c new file mode 100644 index 000000000000..6c3add451761 --- /dev/null +++ b/math/aarch64/sve/log10f.c @@ -0,0 +1,102 @@ +/* + * Single-precision SVE log10 function. + * + * Copyright (c) 2022-2024, Arm Limited. + * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception + */ + +#include "sv_math.h" +#include "test_sig.h" +#include "test_defs.h" + +static const struct data +{ + float poly_0246[4]; + float poly_1357[4]; + float ln2, inv_ln10; + uint32_t off, lower; +} data = { + .poly_1357 = { + /* Coefficients copied from the AdvSIMD routine, then rearranged so that coeffs + 1, 3, 5 and 7 can be loaded as a single quad-word, hence used with _lane + variant of MLA intrinsic. */ + 0x1.2879c8p-3f, 0x1.6408f8p-4f, 0x1.f0e514p-5f, 0x1.f5f76ap-5f + }, + .poly_0246 = { -0x1.bcb79cp-3f, -0x1.bcd472p-4f, -0x1.246f8p-4f, + -0x1.0fc92cp-4f }, + .ln2 = 0x1.62e43p-1f, + .inv_ln10 = 0x1.bcb7b2p-2f, + .off = 0x3f2aaaab, + /* Lower bound is the smallest positive normal float 0x00800000. For + optimised register use subnormals are detected after offset has been + subtracted, so lower bound is 0x0080000 - offset (which wraps around). */ + .lower = 0x00800000 - 0x3f2aaaab +}; + +#define Thres 0x7f000000 /* asuint32(inf) - 0x00800000. */ +#define MantissaMask 0x007fffff + +static svfloat32_t NOINLINE +special_case (svuint32_t u_off, svfloat32_t p, svfloat32_t r2, svfloat32_t y, + svbool_t cmp) +{ + return sv_call_f32 ( + log10f, svreinterpret_f32 (svadd_x (svptrue_b32 (), u_off, data.off)), + svmla_x (svptrue_b32 (), p, r2, y), cmp); +} + +/* Optimised implementation of SVE log10f using the same algorithm and + polynomial as AdvSIMD log10f. + Maximum error is 3.31ulps: + SV_NAME_F1 (log10)(0x1.555c16p+0) got 0x1.ffe2fap-4 + want 0x1.ffe2f4p-4. */ +svfloat32_t SV_NAME_F1 (log10) (svfloat32_t x, const svbool_t pg) +{ + const struct data *d = ptr_barrier (&data); + + svuint32_t u_off = svreinterpret_u32 (x); + + u_off = svsub_x (pg, u_off, d->off); + svbool_t special = svcmpge (pg, svsub_x (pg, u_off, d->lower), Thres); + + /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ + svfloat32_t n = svcvt_f32_x ( + pg, svasr_x (pg, svreinterpret_s32 (u_off), 23)); /* signextend. */ + svuint32_t ix = svand_x (pg, u_off, MantissaMask); + ix = svadd_x (pg, ix, d->off); + svfloat32_t r = svsub_x (pg, svreinterpret_f32 (ix), 1.0f); + + /* y = log10(1+r) + n*log10(2) + log10(1+r) ~ r * InvLn(10) + P(r) + where P(r) is a polynomial. 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). */ + svfloat32_t r2 = svmul_x (svptrue_b32 (), r, r); + svfloat32_t r4 = svmul_x (svptrue_b32 (), r2, r2); + svfloat32_t p_1357 = svld1rq (svptrue_b32 (), &d->poly_1357[0]); + svfloat32_t q_01 = svmla_lane (sv_f32 (d->poly_0246[0]), r, p_1357, 0); + svfloat32_t q_23 = svmla_lane (sv_f32 (d->poly_0246[1]), r, p_1357, 1); + svfloat32_t q_45 = svmla_lane (sv_f32 (d->poly_0246[2]), r, p_1357, 2); + svfloat32_t q_67 = svmla_lane (sv_f32 (d->poly_0246[3]), r, p_1357, 3); + svfloat32_t q_47 = svmla_x (pg, q_45, r2, q_67); + svfloat32_t q_03 = svmla_x (pg, q_01, r2, q_23); + svfloat32_t y = svmla_x (pg, q_03, r4, q_47); + + /* Using hi = Log10(2)*n + r*InvLn(10) is faster but less accurate. */ + svfloat32_t hi = svmla_x (pg, r, n, d->ln2); + hi = svmul_x (pg, hi, d->inv_ln10); + + if (unlikely (svptest_any (pg, special))) + return special_case (u_off, hi, r2, y, special); + return svmla_x (svptrue_b32 (), hi, r2, y); +} + +TEST_SIG (SV, F, 1, log10, 0.01, 11.1) +TEST_ULP (SV_NAME_F1 (log10), 2.82) +TEST_DISABLE_FENV (SV_NAME_F1 (log10)) +TEST_INTERVAL (SV_NAME_F1 (log10), -0.0, -0x1p126, 100) +TEST_INTERVAL (SV_NAME_F1 (log10), 0x1p-149, 0x1p-126, 4000) +TEST_INTERVAL (SV_NAME_F1 (log10), 0x1p-126, 0x1p-23, 50000) +TEST_INTERVAL (SV_NAME_F1 (log10), 0x1p-23, 1.0, 50000) +TEST_INTERVAL (SV_NAME_F1 (log10), 1.0, 100, 50000) +TEST_INTERVAL (SV_NAME_F1 (log10), 100, inf, 50000) +CLOSE_SVE_ATTR |