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Diffstat (limited to 'pl/math/sv_powi.c')
-rw-r--r-- | pl/math/sv_powi.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/pl/math/sv_powi.c b/pl/math/sv_powi.c new file mode 100644 index 0000000..1bb0eb3 --- /dev/null +++ b/pl/math/sv_powi.c @@ -0,0 +1,53 @@ +/* + * Double-precision SVE powi(x, n) function. + * + * Copyright (c) 2020-2023, Arm Limited. + * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception + */ + +#include "sv_math.h" +#if SV_SUPPORTED + +/* Optimized double-precision vector powi (double base, long integer power). + powi is developed for environments in which accuracy is of much less + importance than performance, hence we provide no estimate for worst-case + error. */ +svfloat64_t +__sv_powi_x (svfloat64_t as, svint64_t ns, svbool_t p) +{ + /* Compute powi by successive squaring, right to left. */ + svfloat64_t acc = svdup_n_f64 (1.0); + svbool_t want_recip = svcmplt_n_s64 (p, ns, 0); + svuint64_t ns_abs = svreinterpret_u64_s64 (svabs_s64_x (p, ns)); + + /* We use a max to avoid needing to check whether any lane != 0 on each + iteration. */ + uint64_t max_n = svmaxv_u64 (p, ns_abs); + + svfloat64_t c = as; + /* Successively square c, and use merging predication (_m) to determine + whether or not to perform the multiplication or keep the previous + iteration. */ + while (true) + { + svbool_t px = svcmpeq_n_u64 (p, svand_n_u64_x (p, ns_abs, 1ull), 1ull); + acc = svmul_f64_m (px, acc, c); + max_n >>= 1; + if (max_n == 0) + break; + + ns_abs = svlsr_n_u64_x (p, ns_abs, 1); + c = svmul_f64_x (p, c, c); + } + + /* Negative powers are handled by computing the abs(n) version and then + taking the reciprocal. */ + if (svptest_any (want_recip, want_recip)) + acc = svdivr_n_f64_m (want_recip, acc, 1.0); + + return acc; +} + +strong_alias (__sv_powi_x, _ZGVsMxvv_powk) + +#endif // SV_SUPPORTED |