1*f3087befSAndrew Turner /*
2*f3087befSAndrew Turner * Single-precision vector log function - inline version
3*f3087befSAndrew Turner *
4*f3087befSAndrew Turner * Copyright (c) 2019-2024, Arm Limited.
5*f3087befSAndrew Turner * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
6*f3087befSAndrew Turner */
7*f3087befSAndrew Turner
8*f3087befSAndrew Turner #include "v_math.h"
9*f3087befSAndrew Turner
10*f3087befSAndrew Turner struct v_logf_data
11*f3087befSAndrew Turner {
12*f3087befSAndrew Turner float32x4_t poly[7];
13*f3087befSAndrew Turner float32x4_t ln2;
14*f3087befSAndrew Turner uint32x4_t off, mantissa_mask;
15*f3087befSAndrew Turner };
16*f3087befSAndrew Turner
17*f3087befSAndrew Turner #define V_LOGF_CONSTANTS \
18*f3087befSAndrew Turner { \
19*f3087befSAndrew Turner .poly \
20*f3087befSAndrew Turner = { V4 (-0x1.3e737cp-3f), V4 (0x1.5a9aa2p-3f), V4 (-0x1.4f9934p-3f), \
21*f3087befSAndrew Turner V4 (0x1.961348p-3f), V4 (-0x1.00187cp-2f), V4 (0x1.555d7cp-2f), \
22*f3087befSAndrew Turner V4 (-0x1.ffffc8p-2f) }, \
23*f3087befSAndrew Turner .ln2 = V4 (0x1.62e43p-1f), .off = V4 (0x3f2aaaab), \
24*f3087befSAndrew Turner .mantissa_mask = V4 (0x007fffff) \
25*f3087befSAndrew Turner }
26*f3087befSAndrew Turner
27*f3087befSAndrew Turner #define P(i) d->poly[7 - i]
28*f3087befSAndrew Turner
29*f3087befSAndrew Turner static inline float32x4_t
v_logf_inline(float32x4_t x,const struct v_logf_data * d)30*f3087befSAndrew Turner v_logf_inline (float32x4_t x, const struct v_logf_data *d)
31*f3087befSAndrew Turner {
32*f3087befSAndrew Turner float32x4_t n, p, q, r, r2, y;
33*f3087befSAndrew Turner uint32x4_t u;
34*f3087befSAndrew Turner
35*f3087befSAndrew Turner u = vreinterpretq_u32_f32 (x);
36*f3087befSAndrew Turner
37*f3087befSAndrew Turner /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */
38*f3087befSAndrew Turner u = vsubq_u32 (u, d->off);
39*f3087befSAndrew Turner n = vcvtq_f32_s32 (
40*f3087befSAndrew Turner vshrq_n_s32 (vreinterpretq_s32_u32 (u), 23)); /* signextend. */
41*f3087befSAndrew Turner u = vandq_u32 (u, d->mantissa_mask);
42*f3087befSAndrew Turner u = vaddq_u32 (u, d->off);
43*f3087befSAndrew Turner r = vsubq_f32 (vreinterpretq_f32_u32 (u), v_f32 (1.0f));
44*f3087befSAndrew Turner
45*f3087befSAndrew Turner /* y = log(1+r) + n*ln2. */
46*f3087befSAndrew Turner r2 = vmulq_f32 (r, r);
47*f3087befSAndrew Turner /* n*ln2 + r + r2*(P1 + r*P2 + r2*(P3 + r*P4 + r2*(P5 + r*P6 + r2*P7))). */
48*f3087befSAndrew Turner p = vfmaq_f32 (P (5), P (6), r);
49*f3087befSAndrew Turner q = vfmaq_f32 (P (3), P (4), r);
50*f3087befSAndrew Turner y = vfmaq_f32 (P (1), P (2), r);
51*f3087befSAndrew Turner p = vfmaq_f32 (p, P (7), r2);
52*f3087befSAndrew Turner q = vfmaq_f32 (q, p, r2);
53*f3087befSAndrew Turner y = vfmaq_f32 (y, q, r2);
54*f3087befSAndrew Turner p = vfmaq_f32 (r, d->ln2, n);
55*f3087befSAndrew Turner
56*f3087befSAndrew Turner return vfmaq_f32 (p, y, r2);
57*f3087befSAndrew Turner }
58*f3087befSAndrew Turner
59*f3087befSAndrew Turner #undef P
60