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/*
* 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
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