1 /* 2 * Single-precision vector log function - inline version 3 * 4 * Copyright (c) 2019-2023, Arm Limited. 5 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception 6 */ 7 8 #include "v_math.h" 9 10 struct v_logf_data 11 { 12 float32x4_t poly[7]; 13 float32x4_t ln2; 14 uint32x4_t off, mantissa_mask; 15 }; 16 17 #define V_LOGF_CONSTANTS \ 18 { \ 19 .poly \ 20 = { V4 (-0x1.3e737cp-3f), V4 (0x1.5a9aa2p-3f), V4 (-0x1.4f9934p-3f), \ 21 V4 (0x1.961348p-3f), V4 (-0x1.00187cp-2f), V4 (0x1.555d7cp-2f), \ 22 V4 (-0x1.ffffc8p-2f) }, \ 23 .ln2 = V4 (0x1.62e43p-1f), .off = V4 (0x3f2aaaab), \ 24 .mantissa_mask = V4 (0x007fffff) \ 25 } 26 27 #define P(i) d->poly[7 - i] 28 29 static inline float32x4_t 30 v_logf_inline (float32x4_t x, const struct v_logf_data *d) 31 { 32 float32x4_t n, p, q, r, r2, y; 33 uint32x4_t u; 34 35 u = vreinterpretq_u32_f32 (x); 36 37 /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */ 38 u = vsubq_u32 (u, d->off); 39 n = vcvtq_f32_s32 ( 40 vshrq_n_s32 (vreinterpretq_s32_u32 (u), 23)); /* signextend. */ 41 u = vandq_u32 (u, d->mantissa_mask); 42 u = vaddq_u32 (u, d->off); 43 r = vsubq_f32 (vreinterpretq_f32_u32 (u), v_f32 (1.0f)); 44 45 /* y = log(1+r) + n*ln2. */ 46 r2 = vmulq_f32 (r, r); 47 /* n*ln2 + r + r2*(P1 + r*P2 + r2*(P3 + r*P4 + r2*(P5 + r*P6 + r2*P7))). */ 48 p = vfmaq_f32 (P (5), P (6), r); 49 q = vfmaq_f32 (P (3), P (4), r); 50 y = vfmaq_f32 (P (1), P (2), r); 51 p = vfmaq_f32 (p, P (7), r2); 52 q = vfmaq_f32 (q, p, r2); 53 y = vfmaq_f32 (y, q, r2); 54 p = vfmaq_f32 (r, d->ln2, n); 55 56 return vfmaq_f32 (p, y, r2); 57 } 58 59 #undef P 60