48 lines
1.4 KiB
C
48 lines
1.4 KiB
C
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/*
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* Single-precision polynomial evaluation function for SVE atan(x) and
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* atan2(y,x).
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*
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* Copyright (c) 2021-2023, 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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#ifndef PL_MATH_SV_ATANF_COMMON_H
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#define PL_MATH_SV_ATANF_COMMON_H
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#include "math_config.h"
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#include "sv_math.h"
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#define P(i) sv_f32 (__atanf_poly_data.poly[i])
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/* Polynomial used in fast SVE atanf(x) and atan2f(y,x) implementations
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The order 7 polynomial P approximates (f(sqrt(x))-sqrt(x))/x^(3/2). */
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static inline sv_f32_t
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__sv_atanf_common (svbool_t pg, svbool_t red, sv_f32_t z, sv_f32_t az,
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sv_f32_t shift)
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{
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/* Use full Estrin scheme for P(z^2) with deg(P)=7. */
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/* First compute square powers of z. */
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sv_f32_t z2 = svmul_f32_x (pg, z, z);
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sv_f32_t z4 = svmul_f32_x (pg, z2, z2);
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sv_f32_t z8 = svmul_f32_x (pg, z4, z4);
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/* Then assemble polynomial. */
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sv_f32_t p_4_7 = sv_fma_f32_x (pg, z4, (sv_fma_f32_x (pg, z2, P (7), P (6))),
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(sv_fma_f32_x (pg, z2, P (5), P (4))));
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sv_f32_t p_0_3 = sv_fma_f32_x (pg, z4, (sv_fma_f32_x (pg, z2, P (3), P (2))),
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(sv_fma_f32_x (pg, z2, P (1), P (0))));
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sv_f32_t y = sv_fma_f32_x (pg, z8, p_4_7, p_0_3);
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/* Finalize. y = shift + z + z^3 * P(z^2). */
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sv_f32_t z3 = svmul_f32_x (pg, z2, az);
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y = sv_fma_f32_x (pg, y, z3, az);
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/* Apply shift as indicated by 'red' predicate. */
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y = svadd_f32_m (red, y, shift);
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return y;
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}
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#endif // PL_MATH_SV_ATANF_COMMON_H
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