newlib-cygwin/newlib/libm/machine/spu/headers/erfcf4.h

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/* PROLOG END TAG zYx                                              */
#ifdef __SPU__
#ifndef _ERFCF4_H_
#define _ERFCF4_H_	1

#include <spu_intrinsics.h>

#include "expf4.h"
#include "recipf4.h"
#include "divf4.h"
#include "erf_utils.h"

/*
 * FUNCTION
 *  vector float _erfcf4(vector float x)
 *
 * DESCRIPTION
 *  The erfcf4 function computes the complement error function of each element of x.
 *
 *  C99 Special Cases:
 *  - erfc(+0) returns +1
 *  - erfc(-0) returns +1
 *  - erfc(+infinite) returns +0
 *  - erfc(-infinite) returns +2
 *
 */

static __inline vector float _erfcf4(vector float x)
{
  vec_float4 onehalff  = spu_splats(0.5f);
  vec_float4 zerof     = spu_splats(0.0f);
  vec_float4 onef      = spu_splats(1.0f);
  vec_float4 twof      = spu_splats(2.0f);
  vec_float4 sign_mask = spu_splats(-0.0f);

  /* This is where we switch from near zero approx. */
  vec_float4 approx_point = spu_splats(0.89f);

  vec_float4 xabs, xsqu, xsign;
  vec_uint4  isneg;
  vec_float4 tresult, presult, result;

  xsign = spu_and(x, sign_mask);

  /* Force Denorms to 0 */
  x = spu_add(x, zerof);

  xabs = spu_andc(x, sign_mask);
  xsqu = spu_mul(x, x);

  /*
   * Use Taylor Series for x near 0
   * Preserve sign of x in result, since erf(-x) = -erf(x)
   * This approximation is for erf, so adjust for erfc.
   */
  TAYLOR_ERFF4(xabs, xsqu, tresult);
  tresult = spu_or(tresult, xsign);
  tresult = spu_sub(onef, tresult);

  /*
   * Now, use the Continued Fractions approximation away
   * from 0. If x < 0, use erfc(-x) = 2 - erfc(x)
   */
  CONTFRAC_ERFCF4(xabs, xsqu, presult);
  isneg = spu_rlmaska((vec_uint4)x, -32);
  presult = spu_sel(presult, spu_sub(twof, presult), isneg);

  /*
   * Select the appropriate approximation.
   */
  result = spu_sel(tresult, presult, spu_cmpgt(xabs, approx_point));

  /*
   * Special cases/errors.
   */

  /* x = +/- infinite */
  result = spu_sel(result, zerof, spu_cmpeq((vec_uint4)xabs, 0x7F800000));
  result = spu_sel(result, twof,  spu_cmpeq((vec_uint4)xabs, 0xFF800000));

  return result;
}

#endif /* _ERFCF4_H_ */
#endif /* __SPU__ */