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/*
* Single-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 single-precision vector powi (float base, 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. */
svfloat32_t
__sv_powif_x (svfloat32_t as, svint32_t ns, svbool_t p)
{
/* Compute powi by successive squaring, right to left. */
svfloat32_t acc = svdup_n_f32 (1.f);
svbool_t want_recip = svcmplt_n_s32 (p, ns, 0);
svuint32_t ns_abs = svreinterpret_u32_s32 (svabs_s32_x (p, ns));
/* We use a max to avoid needing to check whether any lane != 0 on each
iteration. */
uint32_t max_n = svmaxv_u32 (p, ns_abs);
svfloat32_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_u32 (p, svand_n_u32_x (p, ns_abs, 1), 1);
acc = svmul_f32_m (px, acc, c);
max_n >>= 1;
if (max_n == 0)
break;
ns_abs = svlsr_n_u32_x (p, ns_abs, 1);
c = svmul_f32_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_f32_m (want_recip, acc, 1.0f);
return acc;
}
/* Note no trailing f for ZGV... name - 64-bit integer version is powk. */
strong_alias (__sv_powif_x, _ZGVsMxvv_powi)
#endif // SV_SUPPORTED
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