diff options
Diffstat (limited to 'contrib/arm-optimized-routines/math/aarch64/sve/log.c')
| -rw-r--r-- | contrib/arm-optimized-routines/math/aarch64/sve/log.c | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/contrib/arm-optimized-routines/math/aarch64/sve/log.c b/contrib/arm-optimized-routines/math/aarch64/sve/log.c new file mode 100644 index 000000000000..c612df48c1fd --- /dev/null +++ b/contrib/arm-optimized-routines/math/aarch64/sve/log.c @@ -0,0 +1,97 @@ +/* + * Double-precision SVE log(x) function. + * + * Copyright (c) 2020-2024, 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" + +#define N (1 << V_LOG_TABLE_BITS) +#define Max (0x7ff0000000000000) +#define Min (0x0010000000000000) +#define Thresh (0x7fe0000000000000) /* Max - Min. */ + +static const struct data +{ + double c0, c2; + double c1, c3; + double ln2, c4; + uint64_t off; +} data = { + .c0 = -0x1.ffffffffffff7p-2, + .c1 = 0x1.55555555170d4p-2, + .c2 = -0x1.0000000399c27p-2, + .c3 = 0x1.999b2e90e94cap-3, + .c4 = -0x1.554e550bd501ep-3, + .ln2 = 0x1.62e42fefa39efp-1, + .off = 0x3fe6900900000000, +}; + +static svfloat64_t NOINLINE +special_case (svfloat64_t hi, svuint64_t tmp, svfloat64_t y, svfloat64_t r2, + svbool_t special, const struct data *d) +{ + svfloat64_t x = svreinterpret_f64 (svadd_x (svptrue_b64 (), tmp, d->off)); + return sv_call_f64 (log, x, svmla_x (svptrue_b64 (), hi, r2, y), special); +} + +/* Double-precision SVE log routine. + Maximum measured error is 2.64 ulp: + SV_NAME_D1 (log)(0x1.95e54bc91a5e2p+184) got 0x1.fffffffe88cacp+6 + want 0x1.fffffffe88cafp+6. */ +svfloat64_t SV_NAME_D1 (log) (svfloat64_t x, const svbool_t pg) +{ + const struct data *d = ptr_barrier (&data); + + svuint64_t ix = svreinterpret_u64 (x); + svbool_t special = svcmpge (pg, svsub_x (pg, ix, Min), Thresh); + + /* x = 2^k z; where z is in range [Off,2*Off) and exact. + The range is split into N subintervals. + The ith subinterval contains z and c is near its center. */ + svuint64_t tmp = svsub_x (pg, ix, d->off); + /* Calculate table index = (tmp >> (52 - V_LOG_TABLE_BITS)) % N. + The actual value of i is double this due to table layout. */ + svuint64_t i + = svand_x (pg, svlsr_x (pg, tmp, (51 - V_LOG_TABLE_BITS)), (N - 1) << 1); + svuint64_t iz = svsub_x (pg, ix, svand_x (pg, tmp, 0xfffULL << 52)); + svfloat64_t z = svreinterpret_f64 (iz); + /* Lookup in 2 global lists (length N). */ + svfloat64_t invc = svld1_gather_index (pg, &__v_log_data.table[0].invc, i); + svfloat64_t logc = svld1_gather_index (pg, &__v_log_data.table[0].logc, i); + + /* log(x) = log1p(z/c-1) + log(c) + k*Ln2. */ + svfloat64_t kd = svcvt_f64_x (pg, svasr_x (pg, svreinterpret_s64 (tmp), 52)); + /* hi = r + log(c) + k*Ln2. */ + svfloat64_t ln2_and_c4 = svld1rq_f64 (svptrue_b64 (), &d->ln2); + svfloat64_t r = svmad_x (pg, invc, z, -1); + svfloat64_t hi = svmla_lane_f64 (logc, kd, ln2_and_c4, 0); + hi = svadd_x (pg, r, hi); + + /* y = r2*(A0 + r*A1 + r2*(A2 + r*A3 + r2*A4)) + hi. */ + svfloat64_t odd_coeffs = svld1rq_f64 (svptrue_b64 (), &d->c1); + svfloat64_t r2 = svmul_x (svptrue_b64 (), r, r); + svfloat64_t y = svmla_lane_f64 (sv_f64 (d->c2), r, odd_coeffs, 1); + svfloat64_t p = svmla_lane_f64 (sv_f64 (d->c0), r, odd_coeffs, 0); + y = svmla_lane_f64 (y, r2, ln2_and_c4, 1); + y = svmla_x (pg, p, r2, y); + + if (unlikely (svptest_any (pg, special))) + return special_case (hi, tmp, y, r2, special, d); + return svmla_x (pg, hi, r2, y); +} + +TEST_SIG (SV, D, 1, log, 0.01, 11.1) +TEST_ULP (SV_NAME_D1 (log), 2.15) +TEST_DISABLE_FENV (SV_NAME_D1 (log)) +TEST_INTERVAL (SV_NAME_D1 (log), -0.0, -inf, 1000) +TEST_INTERVAL (SV_NAME_D1 (log), 0, 0x1p-149, 1000) +TEST_INTERVAL (SV_NAME_D1 (log), 0x1p-149, 0x1p-126, 4000) +TEST_INTERVAL (SV_NAME_D1 (log), 0x1p-126, 0x1p-23, 50000) +TEST_INTERVAL (SV_NAME_D1 (log), 0x1p-23, 1.0, 50000) +TEST_INTERVAL (SV_NAME_D1 (log), 1.0, 100, 50000) +TEST_INTERVAL (SV_NAME_D1 (log), 100, inf, 50000) +CLOSE_SVE_ATTR |