1 /* 2 * Double-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 10 /* Optimized double-precision vector powi (double base, long integer power). 11 powi is developed for environments in which accuracy is of much less 12 importance than performance, hence we provide no estimate for worst-case 13 error. */ 14 svfloat64_t 15 _ZGVsMxvv_powk (svfloat64_t as, svint64_t ns, svbool_t p) 16 { 17 /* Compute powi by successive squaring, right to left. */ 18 svfloat64_t acc = sv_f64 (1.0); 19 svbool_t want_recip = svcmplt (p, ns, 0); 20 svuint64_t ns_abs = svreinterpret_u64 (svabs_x (p, ns)); 21 22 /* We use a max to avoid needing to check whether any lane != 0 on each 23 iteration. */ 24 uint64_t max_n = svmaxv (p, ns_abs); 25 26 svfloat64_t c = as; 27 /* Successively square c, and use merging predication (_m) to determine 28 whether or not to perform the multiplication or keep the previous 29 iteration. */ 30 while (true) 31 { 32 svbool_t px = svcmpeq (p, svand_x (p, ns_abs, 1ull), 1ull); 33 acc = svmul_m (px, acc, c); 34 max_n >>= 1; 35 if (max_n == 0) 36 break; 37 38 ns_abs = svlsr_x (p, ns_abs, 1); 39 c = svmul_x (p, c, c); 40 } 41 42 /* Negative powers are handled by computing the abs(n) version and then 43 taking the reciprocal. */ 44 if (svptest_any (want_recip, want_recip)) 45 acc = svdivr_m (want_recip, acc, 1.0); 46 47 return acc; 48 } 49