1 /* 2 * Helper for SVE routines which calculate log(1 + x) and do not 3 * need special-case handling 4 * 5 * Copyright (c) 2023, Arm Limited. 6 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception 7 */ 8 9 #ifndef PL_MATH_SV_LOG1PF_INLINE_H 10 #define PL_MATH_SV_LOG1PF_INLINE_H 11 12 #include "v_math.h" 13 #include "math_config.h" 14 #include "poly_sve_f32.h" 15 16 static const struct sv_log1pf_data 17 { 18 float32_t poly[9]; 19 float32_t ln2; 20 float32_t scale_back; 21 } sv_log1pf_data = { 22 /* Polynomial generated using FPMinimax in [-0.25, 0.5]. */ 23 .poly = { -0x1p-1f, 0x1.5555aap-2f, -0x1.000038p-2f, 0x1.99675cp-3f, 24 -0x1.54ef78p-3f, 0x1.28a1f4p-3f, -0x1.0da91p-3f, 0x1.abcb6p-4f, 25 -0x1.6f0d5ep-5f }, 26 .scale_back = 0x1.0p-23f, 27 .ln2 = 0x1.62e43p-1f, 28 }; 29 30 static inline svfloat32_t 31 eval_poly (svfloat32_t m, const float32_t *c, svbool_t pg) 32 { 33 svfloat32_t p_12 = svmla_x (pg, sv_f32 (c[0]), m, sv_f32 (c[1])); 34 svfloat32_t m2 = svmul_x (pg, m, m); 35 svfloat32_t q = svmla_x (pg, m, m2, p_12); 36 svfloat32_t p = sv_pw_horner_6_f32_x (pg, m, m2, c + 2); 37 p = svmul_x (pg, m2, p); 38 39 return svmla_x (pg, q, m2, p); 40 } 41 42 static inline svfloat32_t 43 sv_log1pf_inline (svfloat32_t x, svbool_t pg) 44 { 45 const struct sv_log1pf_data *d = ptr_barrier (&sv_log1pf_data); 46 47 svfloat32_t m = svadd_x (pg, x, 1.0f); 48 49 svint32_t ks = svsub_x (pg, svreinterpret_s32 (m), 50 svreinterpret_s32 (svdup_f32 (0.75f))); 51 ks = svand_x (pg, ks, 0xff800000); 52 svuint32_t k = svreinterpret_u32 (ks); 53 svfloat32_t s = svreinterpret_f32 ( 54 svsub_x (pg, svreinterpret_u32 (svdup_f32 (4.0f)), k)); 55 56 svfloat32_t m_scale 57 = svreinterpret_f32 (svsub_x (pg, svreinterpret_u32 (x), k)); 58 m_scale 59 = svadd_x (pg, m_scale, svmla_x (pg, sv_f32 (-1.0f), sv_f32 (0.25f), s)); 60 svfloat32_t p = eval_poly (m_scale, d->poly, pg); 61 svfloat32_t scale_back = svmul_x (pg, svcvt_f32_x (pg, k), d->scale_back); 62 return svmla_x (pg, p, scale_back, d->ln2); 63 } 64 65 #endif // PL_MATH_SV_LOG1PF_INLINE_H