/* Single-precision vector (Advanced SIMD) tanh function

   Copyright (C) 2024-2026 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include "v_expm1f_inline.h"

static const struct data
{
  struct v_expm1f_data expm1f_consts;
  uint32x4_t boring_bound, large_bound, onef;
} data = {
  .expm1f_consts = V_EXPM1F_DATA,
  /* 0x1.205966p+3, above which tanhf rounds to 1 (or -1 for  negative).  */
  .boring_bound = V4 (0x41102cb3),
  .large_bound = V4 (0x7f800000),
};

static float32x4_t NOINLINE VPCS_ATTR
special_case (float32x4_t x, uint32x4_t is_boring, float32x4_t boring,
	      float32x4_t q, uint32x4_t special)
{
  return v_call_f32 (
      tanhf, x,
      vbslq_f32 (is_boring, boring, vdivq_f32 (q, vaddq_f32 (q, v_f32 (2.0)))),
      special);
}

/* Approximation for single-precision vector tanh(x), using a simplified
   version of expm1f. The maximum error is 2.58 ULP:
   _ZGVnN4v_tanhf (0x1.fa5eep-5) got 0x1.f9ba02p-5
				want 0x1.f9ba08p-5.  */
float32x4_t VPCS_ATTR NOINLINE V_NAME_F1 (tanh) (float32x4_t x)
{
  const struct data *d = ptr_barrier (&data);

  uint32x4_t ix = vreinterpretq_u32_f32 (x);
  float32x4_t ax = vabsq_f32 (x);
  uint32x4_t iax = vreinterpretq_u32_f32 (ax);
  uint32x4_t sign = veorq_u32 (ix, iax);
  uint32x4_t is_boring = vcgtq_u32 (iax, d->boring_bound);
  /* expm1 exponent bias is 1.0f reinterpreted to int.  */
  float32x4_t boring = vreinterpretq_f32_u32 (vorrq_u32 (
      sign, vreinterpretq_u32_s32 (d->expm1f_consts.exponent_bias)));

  uint32x4_t special = vcgtq_u32 (iax, d->large_bound);

  /* tanh(x) = (e^2x - 1) / (e^2x + 1).  */
  float32x4_t q = expm1f_inline (vmulq_n_f32 (x, 2), &d->expm1f_consts);

  if (__glibc_unlikely (v_any_u32 (special)))
    return special_case (vreinterpretq_f32_u32 (ix), is_boring, boring, q,
			 special);

  float32x4_t y = vdivq_f32 (q, vaddq_f32 (q, v_f32 (2.0)));
  return vbslq_f32 (is_boring, boring, y);
}
libmvec_hidden_def (V_NAME_F1 (tanh))
HALF_WIDTH_ALIAS_F1 (tanh)
