diff options
Diffstat (limited to 'pl/math/sv_logf_3u4.c')
-rw-r--r-- | pl/math/sv_logf_3u4.c | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/pl/math/sv_logf_3u4.c b/pl/math/sv_logf_3u4.c new file mode 100644 index 0000000..11f0b8a --- /dev/null +++ b/pl/math/sv_logf_3u4.c @@ -0,0 +1,77 @@ +/* + * Single-precision vector log function. + * + * Copyright (c) 2019-2023, 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" + +#if SV_SUPPORTED + +#define P(i) __sv_logf_poly[i] + +#define Ln2 (0x1.62e43p-1f) /* 0x3f317218 */ +#define Min (0x00800000) +#define Max (0x7f800000) +#define Mask (0x007fffff) +#define Off (0x3f2aaaab) /* 0.666667 */ + +float +optr_aor_log_f32 (float); + +static NOINLINE sv_f32_t +__sv_logf_specialcase (sv_f32_t x, sv_f32_t y, svbool_t cmp) +{ + return sv_call_f32 (optr_aor_log_f32, x, y, cmp); +} + +/* Optimised implementation of SVE logf, using the same algorithm and polynomial + as the Neon routine in math/. Maximum error is 3.34 ULPs: + __sv_logf(0x1.557298p+0) got 0x1.26edecp-2 + want 0x1.26ede6p-2. */ +sv_f32_t +__sv_logf_x (sv_f32_t x, const svbool_t pg) +{ + sv_u32_t u = sv_as_u32_f32 (x); + svbool_t cmp + = svcmpge_u32 (pg, svsub_n_u32_x (pg, u, Min), sv_u32 (Max - Min)); + + /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ + u = svsub_n_u32_x (pg, u, Off); + sv_f32_t n = sv_to_f32_s32_x (pg, svasr_n_s32_x (pg, sv_as_s32_u32 (u), + 23)); /* Sign-extend. */ + u = svand_n_u32_x (pg, u, Mask); + u = svadd_n_u32_x (pg, u, Off); + sv_f32_t r = svsub_n_f32_x (pg, sv_as_f32_u32 (u), 1.0f); + + /* y = log(1+r) + n*ln2. */ + sv_f32_t r2 = svmul_f32_x (pg, r, r); + /* n*ln2 + r + r2*(P6 + r*P5 + r2*(P4 + r*P3 + r2*(P2 + r*P1 + r2*P0))). */ + sv_f32_t p = sv_fma_n_f32_x (pg, P (1), r, sv_f32 (P (2))); + sv_f32_t q = sv_fma_n_f32_x (pg, P (3), r, sv_f32 (P (4))); + sv_f32_t y = sv_fma_n_f32_x (pg, P (5), r, sv_f32 (P (6))); + p = sv_fma_n_f32_x (pg, P (0), r2, p); + q = sv_fma_f32_x (pg, p, r2, q); + y = sv_fma_f32_x (pg, q, r2, y); + p = sv_fma_n_f32_x (pg, Ln2, n, r); + y = sv_fma_f32_x (pg, y, r2, p); + + if (unlikely (svptest_any (pg, cmp))) + return __sv_logf_specialcase (x, y, cmp); + return y; +} + +PL_ALIAS (__sv_logf_x, _ZGVsMxv_logf) + +PL_SIG (SV, F, 1, log, 0.01, 11.1) +PL_TEST_ULP (__sv_logf, 2.85) +PL_TEST_INTERVAL (__sv_logf, -0.0, -0x1p126, 100) +PL_TEST_INTERVAL (__sv_logf, 0x1p-149, 0x1p-126, 4000) +PL_TEST_INTERVAL (__sv_logf, 0x1p-126, 0x1p-23, 50000) +PL_TEST_INTERVAL (__sv_logf, 0x1p-23, 1.0, 50000) +PL_TEST_INTERVAL (__sv_logf, 1.0, 100, 50000) +PL_TEST_INTERVAL (__sv_logf, 100, inf, 50000) +#endif // SV_SUPPORTED |