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55 lines
1.6 KiB
C
55 lines
1.6 KiB
C
/*
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* Single-precision SVE powi(x, n) function.
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*
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* Copyright (c) 2020-2023, Arm Limited.
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* SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
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*/
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#include "sv_math.h"
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#if SV_SUPPORTED
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/* Optimized single-precision vector powi (float base, integer power).
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powi is developed for environments in which accuracy is of much less
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importance than performance, hence we provide no estimate for worst-case
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error. */
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svfloat32_t
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__sv_powif_x (svfloat32_t as, svint32_t ns, svbool_t p)
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{
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/* Compute powi by successive squaring, right to left. */
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svfloat32_t acc = svdup_n_f32 (1.f);
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svbool_t want_recip = svcmplt_n_s32 (p, ns, 0);
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svuint32_t ns_abs = svreinterpret_u32_s32 (svabs_s32_x (p, ns));
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/* We use a max to avoid needing to check whether any lane != 0 on each
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iteration. */
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uint32_t max_n = svmaxv_u32 (p, ns_abs);
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svfloat32_t c = as;
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/* Successively square c, and use merging predication (_m) to determine
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whether or not to perform the multiplication or keep the previous
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iteration. */
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while (true)
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{
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svbool_t px = svcmpeq_n_u32 (p, svand_n_u32_x (p, ns_abs, 1), 1);
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acc = svmul_f32_m (px, acc, c);
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max_n >>= 1;
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if (max_n == 0)
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break;
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ns_abs = svlsr_n_u32_x (p, ns_abs, 1);
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c = svmul_f32_x (p, c, c);
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}
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/* Negative powers are handled by computing the abs(n) version and then
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taking the reciprocal. */
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if (svptest_any (want_recip, want_recip))
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acc = svdivr_n_f32_m (want_recip, acc, 1.0f);
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return acc;
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}
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/* Note no trailing f for ZGV... name - 64-bit integer version is powk. */
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strong_alias (__sv_powif_x, _ZGVsMxvv_powi)
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#endif // SV_SUPPORTED
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