1*5a02ffc3SAndrew Turner /*
2*5a02ffc3SAndrew Turner * Single-precision vector log function - inline version
3*5a02ffc3SAndrew Turner *
4*5a02ffc3SAndrew Turner * Copyright (c) 2019-2023, Arm Limited.
5*5a02ffc3SAndrew Turner * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
6*5a02ffc3SAndrew Turner */
7*5a02ffc3SAndrew Turner
8*5a02ffc3SAndrew Turner #include "v_math.h"
9*5a02ffc3SAndrew Turner
10*5a02ffc3SAndrew Turner struct v_logf_data
11*5a02ffc3SAndrew Turner {
12*5a02ffc3SAndrew Turner float32x4_t poly[7];
13*5a02ffc3SAndrew Turner float32x4_t ln2;
14*5a02ffc3SAndrew Turner uint32x4_t off, mantissa_mask;
15*5a02ffc3SAndrew Turner };
16*5a02ffc3SAndrew Turner
17*5a02ffc3SAndrew Turner #define V_LOGF_CONSTANTS \
18*5a02ffc3SAndrew Turner { \
19*5a02ffc3SAndrew Turner .poly \
20*5a02ffc3SAndrew Turner = { V4 (-0x1.3e737cp-3f), V4 (0x1.5a9aa2p-3f), V4 (-0x1.4f9934p-3f), \
21*5a02ffc3SAndrew Turner V4 (0x1.961348p-3f), V4 (-0x1.00187cp-2f), V4 (0x1.555d7cp-2f), \
22*5a02ffc3SAndrew Turner V4 (-0x1.ffffc8p-2f) }, \
23*5a02ffc3SAndrew Turner .ln2 = V4 (0x1.62e43p-1f), .off = V4 (0x3f2aaaab), \
24*5a02ffc3SAndrew Turner .mantissa_mask = V4 (0x007fffff) \
25*5a02ffc3SAndrew Turner }
26*5a02ffc3SAndrew Turner
27*5a02ffc3SAndrew Turner #define P(i) d->poly[7 - i]
28*5a02ffc3SAndrew Turner
29*5a02ffc3SAndrew Turner static inline float32x4_t
v_logf_inline(float32x4_t x,const struct v_logf_data * d)30*5a02ffc3SAndrew Turner v_logf_inline (float32x4_t x, const struct v_logf_data *d)
31*5a02ffc3SAndrew Turner {
32*5a02ffc3SAndrew Turner float32x4_t n, p, q, r, r2, y;
33*5a02ffc3SAndrew Turner uint32x4_t u;
34*5a02ffc3SAndrew Turner
35*5a02ffc3SAndrew Turner u = vreinterpretq_u32_f32 (x);
36*5a02ffc3SAndrew Turner
37*5a02ffc3SAndrew Turner /* x = 2^n * (1+r), where 2/3 < 1+r < 4/3. */
38*5a02ffc3SAndrew Turner u = vsubq_u32 (u, d->off);
39*5a02ffc3SAndrew Turner n = vcvtq_f32_s32 (
40*5a02ffc3SAndrew Turner vshrq_n_s32 (vreinterpretq_s32_u32 (u), 23)); /* signextend. */
41*5a02ffc3SAndrew Turner u = vandq_u32 (u, d->mantissa_mask);
42*5a02ffc3SAndrew Turner u = vaddq_u32 (u, d->off);
43*5a02ffc3SAndrew Turner r = vsubq_f32 (vreinterpretq_f32_u32 (u), v_f32 (1.0f));
44*5a02ffc3SAndrew Turner
45*5a02ffc3SAndrew Turner /* y = log(1+r) + n*ln2. */
46*5a02ffc3SAndrew Turner r2 = vmulq_f32 (r, r);
47*5a02ffc3SAndrew Turner /* n*ln2 + r + r2*(P1 + r*P2 + r2*(P3 + r*P4 + r2*(P5 + r*P6 + r2*P7))). */
48*5a02ffc3SAndrew Turner p = vfmaq_f32 (P (5), P (6), r);
49*5a02ffc3SAndrew Turner q = vfmaq_f32 (P (3), P (4), r);
50*5a02ffc3SAndrew Turner y = vfmaq_f32 (P (1), P (2), r);
51*5a02ffc3SAndrew Turner p = vfmaq_f32 (p, P (7), r2);
52*5a02ffc3SAndrew Turner q = vfmaq_f32 (q, p, r2);
53*5a02ffc3SAndrew Turner y = vfmaq_f32 (y, q, r2);
54*5a02ffc3SAndrew Turner p = vfmaq_f32 (r, d->ln2, n);
55*5a02ffc3SAndrew Turner
56*5a02ffc3SAndrew Turner return vfmaq_f32 (p, y, r2);
57*5a02ffc3SAndrew Turner }
58*5a02ffc3SAndrew Turner
59*5a02ffc3SAndrew Turner #undef P
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