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77 lines
1.6 KiB
77 lines
1.6 KiB
/*
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* Single-precision vector cos function.
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*
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* Copyright (c) 2019, Arm Limited.
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* SPDX-License-Identifier: MIT
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*/
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#include "mathlib.h"
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#include "v_math.h"
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#if V_SUPPORTED
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static const float Poly[] = {
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/* 1.886 ulp error */
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0x1.5b2e76p-19f,
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-0x1.9f42eap-13f,
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0x1.110df4p-7f,
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-0x1.555548p-3f,
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};
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#define Pi1 v_f32 (0x1.921fb6p+1f)
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#define Pi2 v_f32 (-0x1.777a5cp-24f)
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#define Pi3 v_f32 (-0x1.ee59dap-49f)
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#define A3 v_f32 (Poly[3])
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#define A5 v_f32 (Poly[2])
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#define A7 v_f32 (Poly[1])
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#define A9 v_f32 (Poly[0])
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#define RangeVal v_f32 (0x1p20f)
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#define InvPi v_f32 (0x1.45f306p-2f)
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#define Shift v_f32 (0x1.8p+23f)
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#define AbsMask v_u32 (0x7fffffff)
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#define HalfPi v_f32 (0x1.921fb6p0f)
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VPCS_ATTR
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static v_f32_t
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specialcase (v_f32_t x, v_f32_t y, v_u32_t cmp)
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{
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/* Fall back to scalar code. */
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return v_call_f32 (cosf, x, y, cmp);
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}
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VPCS_ATTR
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v_f32_t
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V_NAME(cosf) (v_f32_t x)
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{
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v_f32_t n, r, r2, y;
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v_u32_t odd, cmp;
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r = v_as_f32_u32 (v_as_u32_f32 (x) & AbsMask);
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cmp = v_cond_u32 (v_as_u32_f32 (r) >= v_as_u32_f32 (RangeVal));
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/* n = rint((|x|+pi/2)/pi) - 0.5 */
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n = v_fma_f32 (InvPi, r + HalfPi, Shift);
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odd = v_as_u32_f32 (n) << 31;
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n -= Shift;
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n -= v_f32 (0.5f);
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/* r = |x| - n*pi (range reduction into -pi/2 .. pi/2) */
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r = v_fma_f32 (-Pi1, n, r);
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r = v_fma_f32 (-Pi2, n, r);
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r = v_fma_f32 (-Pi3, n, r);
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/* y = sin(r) */
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r2 = r * r;
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y = v_fma_f32 (A9, r2, A7);
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y = v_fma_f32 (y, r2, A5);
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y = v_fma_f32 (y, r2, A3);
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y = v_fma_f32 (y * r2, r, r);
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/* sign fix */
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y = v_as_f32_u32 (v_as_u32_f32 (y) ^ odd);
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if (unlikely (v_any_u32 (cmp)))
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return specialcase (x, y, cmp);
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return y;
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}
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VPCS_ALIAS
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#endif
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