hypotf.c

/*
 * Single-precision vector hypot(x) function.
 *
 * Copyright (c) 2023-2024, Arm Limited.
 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
 */

#include "v_math.h"
#include "test_sig.h"
#include "test_defs.h"

#if WANT_SIMD_EXCEPT
static const struct data
{
  uint32x4_t tiny_bound, thres;
} data = {
  .tiny_bound = V4 (0x20000000), /* asuint (0x1p-63).  */
  .thres = V4 (0x3f000000),	 /* asuint (0x1p63) - tiny_bound.  */
};
#else
static const struct data
{
  uint32x4_t tiny_bound;
  uint16x8_t thres;
} data = {
  .tiny_bound = V4 (0x0C800000), /* asuint (0x1p-102).  */
  .thres = V8 (0x7300),		 /* asuint (inf) - tiny_bound.  */
};
#endif

static float32x4_t VPCS_ATTR NOINLINE
special_case (float32x4_t x, float32x4_t y, float32x4_t sqsum,
	      uint16x4_t special)
{
  return v_call2_f32 (hypotf, x, y, vsqrtq_f32 (sqsum), vmovl_u16 (special));
}

/* Vector implementation of single-precision hypot.
   Maximum error observed is 1.21 ULP:
   _ZGVnN4vv_hypotf (0x1.6a419cp-13, 0x1.82a852p-22) got 0x1.6a41d2p-13
						    want 0x1.6a41dp-13.  */
#if WANT_SIMD_EXCEPT

float32x4_t VPCS_ATTR NOINLINE V_NAME_F2 (hypot) (float32x4_t x, float32x4_t y)
{
  const struct data *d = ptr_barrier (&data);

  float32x4_t ax = vabsq_f32 (x);
  float32x4_t ay = vabsq_f32 (y);

  uint32x4_t ix = vreinterpretq_u32_f32 (ax);
  uint32x4_t iy = vreinterpretq_u32_f32 (ay);

  /* Extreme values, NaNs, and infinities should be handled by the scalar
     fallback for correct flag handling.  */
  uint32x4_t specialx = vcgeq_u32 (vsubq_u32 (ix, d->tiny_bound), d->thres);
  uint32x4_t specialy = vcgeq_u32 (vsubq_u32 (iy, d->tiny_bound), d->thres);
  ax = v_zerofy_f32 (ax, specialx);
  ay = v_zerofy_f32 (ay, specialy);
  uint16x4_t special = vaddhn_u32 (specialx, specialy);

  float32x4_t sqsum = vfmaq_f32 (vmulq_f32 (ax, ax), ay, ay);

  if (unlikely (v_any_u16h (special)))
    return special_case (x, y, sqsum, special);

  return vsqrtq_f32 (sqsum);
}
#else

float32x4_t VPCS_ATTR NOINLINE V_NAME_F2 (hypot) (float32x4_t x, float32x4_t y)
{
  const struct data *d = ptr_barrier (&data);

  float32x4_t sqsum = vfmaq_f32 (vmulq_f32 (x, x), y, y);

  uint16x4_t special
      = vcge_u16 (vsubhn_u32 (vreinterpretq_u32_f32 (sqsum), d->tiny_bound),
		  vget_low_u16 (d->thres));

  if (unlikely (v_any_u16h (special)))
    return special_case (x, y, sqsum, special);

  return vsqrtq_f32 (sqsum);
}
#endif

HALF_WIDTH_ALIAS_F2 (hypot)

TEST_SIG (V, F, 2, hypot, -10.0, 10.0)
TEST_ULP (V_NAME_F2 (hypot), 1.21)
TEST_DISABLE_FENV_IF_NOT (V_NAME_F2 (hypot), WANT_SIMD_EXCEPT)
TEST_INTERVAL2 (V_NAME_F2 (hypot), 0, inf, 0, inf, 10000)
TEST_INTERVAL2 (V_NAME_F2 (hypot), 0, inf, -0, -inf, 10000)
TEST_INTERVAL2 (V_NAME_F2 (hypot), -0, -inf, 0, inf, 10000)
TEST_INTERVAL2 (V_NAME_F2 (hypot), -0, -inf, -0, -inf, 10000)