1 /*
2  * Single-precision SVE powi(x, n) function.
3  *
4  * Copyright (c) 2020-2023, Arm Limited.
5  * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
6  */
7 
8 #include "sv_math.h"
9 #if SV_SUPPORTED
10 
11 /* Optimized single-precision vector powi (float base, integer power).
12    powi is developed for environments in which accuracy is of much less
13    importance than performance, hence we provide no estimate for worst-case
14    error.  */
15 svfloat32_t
16 __sv_powif_x (svfloat32_t as, svint32_t ns, svbool_t p)
17 {
18   /* Compute powi by successive squaring, right to left.  */
19   svfloat32_t acc = svdup_n_f32 (1.f);
20   svbool_t want_recip = svcmplt_n_s32 (p, ns, 0);
21   svuint32_t ns_abs = svreinterpret_u32_s32 (svabs_s32_x (p, ns));
22 
23   /* We use a max to avoid needing to check whether any lane != 0 on each
24      iteration.  */
25   uint32_t max_n = svmaxv_u32 (p, ns_abs);
26 
27   svfloat32_t c = as;
28   /* Successively square c, and use merging predication (_m) to determine
29      whether or not to perform the multiplication or keep the previous
30      iteration.  */
31   while (true)
32     {
33       svbool_t px = svcmpeq_n_u32 (p, svand_n_u32_x (p, ns_abs, 1), 1);
34       acc = svmul_f32_m (px, acc, c);
35       max_n >>= 1;
36       if (max_n == 0)
37 	break;
38 
39       ns_abs = svlsr_n_u32_x (p, ns_abs, 1);
40       c = svmul_f32_x (p, c, c);
41     }
42 
43   /* Negative powers are handled by computing the abs(n) version and then
44      taking the reciprocal.  */
45   if (svptest_any (want_recip, want_recip))
46     acc = svdivr_n_f32_m (want_recip, acc, 1.0f);
47 
48   return acc;
49 }
50 
51 /* Note no trailing f for ZGV... name - 64-bit integer version is powk.  */
52 strong_alias (__sv_powif_x, _ZGVsMxvv_powi)
53 
54 #endif // SV_SUPPORTED
55