diff options
Diffstat (limited to 'contrib/arm-optimized-routines/pl/math/sv_log2f_2u5.c')
-rw-r--r-- | contrib/arm-optimized-routines/pl/math/sv_log2f_2u5.c | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/contrib/arm-optimized-routines/pl/math/sv_log2f_2u5.c b/contrib/arm-optimized-routines/pl/math/sv_log2f_2u5.c new file mode 100644 index 000000000000..9e96c62bbcc6 --- /dev/null +++ b/contrib/arm-optimized-routines/pl/math/sv_log2f_2u5.c @@ -0,0 +1,86 @@ +/* + * Single-precision vector/SVE log2 function. + * + * Copyright (c) 2022-2023, Arm Limited. + * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception + */ + +#include "sv_math.h" +#include "pl_sig.h" +#include "pl_test.h" + +static const struct data +{ + float poly_02468[5]; + float poly_1357[4]; +} 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. */ + -0x1.715458p-1f, -0x1.7171a4p-2f, -0x1.e5143ep-3f, -0x1.c675bp-3f + }, + .poly_02468 = { 0x1.715476p0f, 0x1.ec701cp-2f, 0x1.27a0b8p-2f, + 0x1.9d8ecap-3f, 0x1.9e495p-3f }, +}; + +#define Min (0x00800000) +#define Max (0x7f800000) +#define Thres (0x7f000000) /* Max - Min. */ +#define MantissaMask (0x007fffff) +#define Off (0x3f2aaaab) /* 0.666667. */ + +static svfloat32_t NOINLINE +special_case (svfloat32_t x, svfloat32_t y, svbool_t cmp) +{ + return sv_call_f32 (log2f, x, y, cmp); +} + +/* Optimised implementation of SVE log2f, using the same algorithm + and polynomial as AdvSIMD log2f. + Maximum error is 2.48 ULPs: + SV_NAME_F1 (log2)(0x1.558174p+0) got 0x1.a9be84p-2 + want 0x1.a9be8p-2. */ +svfloat32_t SV_NAME_F1 (log2) (svfloat32_t x, const svbool_t pg) +{ + const struct data *d = ptr_barrier (&data); + + svuint32_t u = svreinterpret_u32 (x); + svbool_t special = svcmpge (pg, svsub_x (pg, u, Min), Thres); + + /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ + u = svsub_x (pg, u, Off); + svfloat32_t n = svcvt_f32_x ( + pg, svasr_x (pg, svreinterpret_s32 (u), 23)); /* Sign-extend. */ + u = svand_x (pg, u, MantissaMask); + u = svadd_x (pg, u, Off); + svfloat32_t r = svsub_x (pg, svreinterpret_f32 (u), 1.0f); + + /* y = log2(1+r) + n. */ + svfloat32_t r2 = svmul_x (pg, r, r); + + /* Evaluate polynomial using pairwise Horner scheme. */ + svfloat32_t p_1357 = svld1rq (svptrue_b32 (), &d->poly_1357[0]); + svfloat32_t q_01 = svmla_lane (sv_f32 (d->poly_02468[0]), r, p_1357, 0); + svfloat32_t q_23 = svmla_lane (sv_f32 (d->poly_02468[1]), r, p_1357, 1); + svfloat32_t q_45 = svmla_lane (sv_f32 (d->poly_02468[2]), r, p_1357, 2); + svfloat32_t q_67 = svmla_lane (sv_f32 (d->poly_02468[3]), r, p_1357, 3); + svfloat32_t y = svmla_x (pg, q_67, r2, sv_f32 (d->poly_02468[4])); + y = svmla_x (pg, q_45, r2, y); + y = svmla_x (pg, q_23, r2, y); + y = svmla_x (pg, q_01, r2, y); + + if (unlikely (svptest_any (pg, special))) + return special_case (x, svmla_x (svnot_z (pg, special), n, r, y), special); + return svmla_x (pg, n, r, y); +} + +PL_SIG (SV, F, 1, log2, 0.01, 11.1) +PL_TEST_ULP (SV_NAME_F1 (log2), 1.99) +PL_TEST_EXPECT_FENV_ALWAYS (SV_NAME_F1 (log2)) +PL_TEST_INTERVAL (SV_NAME_F1 (log2), -0.0, -0x1p126, 4000) +PL_TEST_INTERVAL (SV_NAME_F1 (log2), 0.0, 0x1p-126, 4000) +PL_TEST_INTERVAL (SV_NAME_F1 (log2), 0x1p-126, 0x1p-23, 50000) +PL_TEST_INTERVAL (SV_NAME_F1 (log2), 0x1p-23, 1.0, 50000) +PL_TEST_INTERVAL (SV_NAME_F1 (log2), 1.0, 100, 50000) +PL_TEST_INTERVAL (SV_NAME_F1 (log2), 100, inf, 50000) |