1 /* 2 * Single-precision vector log function. 3 * 4 * Copyright (c) 2019-2023, Arm Limited. 5 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception 6 */ 7 8 #include "sv_math.h" 9 #include "pl_sig.h" 10 #include "pl_test.h" 11 12 #if SV_SUPPORTED 13 14 #define P(i) __sv_logf_poly[i] 15 16 #define Ln2 (0x1.62e43p-1f) /* 0x3f317218 */ 17 #define Min (0x00800000) 18 #define Max (0x7f800000) 19 #define Mask (0x007fffff) 20 #define Off (0x3f2aaaab) /* 0.666667 */ 21 22 float 23 optr_aor_log_f32 (float); 24 25 static NOINLINE sv_f32_t 26 __sv_logf_specialcase (sv_f32_t x, sv_f32_t y, svbool_t cmp) 27 { 28 return sv_call_f32 (optr_aor_log_f32, x, y, cmp); 29 } 30 31 /* Optimised implementation of SVE logf, using the same algorithm and polynomial 32 as the Neon routine in math/. Maximum error is 3.34 ULPs: 33 __sv_logf(0x1.557298p+0) got 0x1.26edecp-2 34 want 0x1.26ede6p-2. */ 35 sv_f32_t 36 __sv_logf_x (sv_f32_t x, const svbool_t pg) 37 { 38 sv_u32_t u = sv_as_u32_f32 (x); 39 svbool_t cmp 40 = svcmpge_u32 (pg, svsub_n_u32_x (pg, u, Min), sv_u32 (Max - Min)); 41 42 /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ 43 u = svsub_n_u32_x (pg, u, Off); 44 sv_f32_t n = sv_to_f32_s32_x (pg, svasr_n_s32_x (pg, sv_as_s32_u32 (u), 45 23)); /* Sign-extend. */ 46 u = svand_n_u32_x (pg, u, Mask); 47 u = svadd_n_u32_x (pg, u, Off); 48 sv_f32_t r = svsub_n_f32_x (pg, sv_as_f32_u32 (u), 1.0f); 49 50 /* y = log(1+r) + n*ln2. */ 51 sv_f32_t r2 = svmul_f32_x (pg, r, r); 52 /* n*ln2 + r + r2*(P6 + r*P5 + r2*(P4 + r*P3 + r2*(P2 + r*P1 + r2*P0))). */ 53 sv_f32_t p = sv_fma_n_f32_x (pg, P (1), r, sv_f32 (P (2))); 54 sv_f32_t q = sv_fma_n_f32_x (pg, P (3), r, sv_f32 (P (4))); 55 sv_f32_t y = sv_fma_n_f32_x (pg, P (5), r, sv_f32 (P (6))); 56 p = sv_fma_n_f32_x (pg, P (0), r2, p); 57 q = sv_fma_f32_x (pg, p, r2, q); 58 y = sv_fma_f32_x (pg, q, r2, y); 59 p = sv_fma_n_f32_x (pg, Ln2, n, r); 60 y = sv_fma_f32_x (pg, y, r2, p); 61 62 if (unlikely (svptest_any (pg, cmp))) 63 return __sv_logf_specialcase (x, y, cmp); 64 return y; 65 } 66 67 PL_ALIAS (__sv_logf_x, _ZGVsMxv_logf) 68 69 PL_SIG (SV, F, 1, log, 0.01, 11.1) 70 PL_TEST_ULP (__sv_logf, 2.85) 71 PL_TEST_INTERVAL (__sv_logf, -0.0, -0x1p126, 100) 72 PL_TEST_INTERVAL (__sv_logf, 0x1p-149, 0x1p-126, 4000) 73 PL_TEST_INTERVAL (__sv_logf, 0x1p-126, 0x1p-23, 50000) 74 PL_TEST_INTERVAL (__sv_logf, 0x1p-23, 1.0, 50000) 75 PL_TEST_INTERVAL (__sv_logf, 1.0, 100, 50000) 76 PL_TEST_INTERVAL (__sv_logf, 100, inf, 50000) 77 #endif // SV_SUPPORTED 78