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/*
* Single-precision vector tanh(x) function.
*
* Copyright (c) 2022-2023, 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 "v_expm1f_inline.h"
#define BoringBound \
0x41102cb3 /* 0x1.205966p+3, above which tanhf rounds to 1 (or -1 for \
negative). */
#define AbsMask 0x7fffffff
static NOINLINE v_f32_t
special_case (v_f32_t x, v_f32_t y, v_u32_t special)
{
return v_call_f32 (tanhf, x, y, special);
}
/* Approximation for single-precision vector tanh(x), using a simplified version
of expm1f. The maximum error is 2.58 ULP:
__v_tanhf(0x1.fa5eep-5) got 0x1.f9ba02p-5
want 0x1.f9ba08p-5. */
VPCS_ATTR v_f32_t V_NAME (tanhf) (v_f32_t x)
{
v_u32_t ix = v_as_u32_f32 (x);
v_u32_t iax = ix & AbsMask;
v_u32_t sign = ix & ~AbsMask;
v_u32_t is_boring = v_cond_u32 (iax > BoringBound);
v_f32_t boring = v_as_f32_u32 (sign | One);
#if WANT_SIMD_EXCEPT
/* If fp exceptions are to be triggered properly, set all special and boring
lanes to 1, which will trigger no exceptions, and fix them up later. */
v_u32_t special = v_cond_u32 ((iax > 0x7f800000) | (iax < 0x34000000));
ix = v_sel_u32 (is_boring, v_u32 (One), ix);
if (unlikely (v_any_u32 (special)))
ix = v_sel_u32 (special, v_u32 (One), ix);
#else
v_u32_t special = v_cond_u32 ((iax > 0x7f800000) | (iax == 0));
#endif
/* tanh(x) = (e^2x - 1) / (e^2x + 1). */
v_f32_t q = expm1f_inline (2 * v_as_f32_u32 (ix));
v_f32_t y = q / (q + 2);
y = v_sel_f32 (is_boring, boring, y);
if (unlikely (v_any_u32 (special)))
return special_case (x, y, special);
return y;
}
VPCS_ALIAS
PL_SIG (V, F, 1, tanh, -10.0, 10.0)
PL_TEST_ULP (V_NAME (tanhf), 2.09)
PL_TEST_EXPECT_FENV (V_NAME (tanhf), WANT_SIMD_EXCEPT)
PL_TEST_INTERVAL (V_NAME (tanhf), 0, 0x1p-23, 1000)
PL_TEST_INTERVAL (V_NAME (tanhf), -0, -0x1p-23, 1000)
PL_TEST_INTERVAL (V_NAME (tanhf), 0x1p-23, 0x1.205966p+3, 100000)
PL_TEST_INTERVAL (V_NAME (tanhf), -0x1p-23, -0x1.205966p+3, 100000)
PL_TEST_INTERVAL (V_NAME (tanhf), 0x1.205966p+3, inf, 100)
PL_TEST_INTERVAL (V_NAME (tanhf), -0x1.205966p+3, -inf, 100)
#endif
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