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/*
* Single-precision vector atan2(x) function.
*
* Copyright (c) 2021-2022, Arm Limited.
* SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
*/
#include "v_math.h"
#include "pl_sig.h"
#include "pl_test.h"
#if V_SUPPORTED
#include "atanf_common.h"
/* Useful constants. */
#define PiOver2 v_f32 (0x1.921fb6p+0f)
#define SignMask v_u32 (0x80000000)
/* Special cases i.e. 0, infinity and nan (fall back to scalar calls). */
VPCS_ATTR
NOINLINE static v_f32_t
specialcase (v_f32_t y, v_f32_t x, v_f32_t ret, v_u32_t cmp)
{
return v_call2_f32 (atan2f, y, x, ret, cmp);
}
/* Returns 1 if input is the bit representation of 0, infinity or nan. */
static inline v_u32_t
zeroinfnan (v_u32_t i)
{
return v_cond_u32 (2 * i - 1 >= v_u32 (2 * 0x7f800000lu - 1));
}
/* Fast implementation of vector atan2f. Maximum observed error is
2.95 ULP in [0x1.9300d6p+6 0x1.93c0c6p+6] x [0x1.8c2dbp+6 0x1.8cea6p+6]:
v_atan2(0x1.93836cp+6, 0x1.8cae1p+6) got 0x1.967f06p-1
want 0x1.967f00p-1. */
VPCS_ATTR
v_f32_t V_NAME (atan2f) (v_f32_t y, v_f32_t x)
{
v_u32_t ix = v_as_u32_f32 (x);
v_u32_t iy = v_as_u32_f32 (y);
v_u32_t special_cases = zeroinfnan (ix) | zeroinfnan (iy);
v_u32_t sign_x = ix & SignMask;
v_u32_t sign_y = iy & SignMask;
v_u32_t sign_xy = sign_x ^ sign_y;
v_f32_t ax = v_abs_f32 (x);
v_f32_t ay = v_abs_f32 (y);
v_u32_t pred_xlt0 = x < 0.0f;
v_u32_t pred_aygtax = ay > ax;
/* Set up z for call to atanf. */
v_f32_t n = v_sel_f32 (pred_aygtax, -ax, ay);
v_f32_t d = v_sel_f32 (pred_aygtax, ay, ax);
v_f32_t z = v_div_f32 (n, d);
/* Work out the correct shift. */
v_f32_t shift = v_sel_f32 (pred_xlt0, v_f32 (-2.0f), v_f32 (0.0f));
shift = v_sel_f32 (pred_aygtax, shift + 1.0f, shift);
shift *= PiOver2;
v_f32_t ret = eval_poly (z, z, shift);
/* Account for the sign of y. */
ret = v_as_f32_u32 (v_as_u32_f32 (ret) ^ sign_xy);
if (unlikely (v_any_u32 (special_cases)))
{
return specialcase (y, x, ret, special_cases);
}
return ret;
}
VPCS_ALIAS
/* Arity of 2 means no mathbench entry emitted. See test/mathbench_funcs.h. */
PL_SIG (V, F, 2, atan2)
PL_TEST_ULP (V_NAME (atan2f), 2.46)
#endif
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