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/* PROLOG END TAG zYx                                              */

#ifdef __SPU__

#ifndef _ASINF4_H_

#define _ASINF4_H_      1

#include <spu_intrinsics.h>

#include "divf4.h"

#include "sqrtf4.h"

/*

 * FUNCTION

 *      vector float _asinf4(vector float x)

 *

 * DESCRIPTION

 *      The _asinf4 function computes the arc sine for a vector of values x;

 *      that is the values whose sine is x. Results are undefined if x is

 *      outside the range [-1, 1].

 *

 */

static __inline vector float _asinf4(vector float x)

{

  /* The arcsin is computed using two different algorithms, depending

   * upon the absolute value of the input. For inputs in the range

   * [0, PI/4], it is computed as the ratio of two polynomials.

   *

   *    asin(x) = p/q;

   *

   *    where p = P11*x^11 + P09*x^9 + P07*x^7 + P05*x^5 + P03*x3 + x

   *          q = Q08*x^8  + Q06*x^6 + Q04*x^4 + Q02*x^2 + Q00

   *

   * For the range of value [PI/4, 1], the arcsin is computed using:

   *

   *    asin = PI/2 - sqrt(1 - x) * r;

   *

   *    where r = C07*x^7 + C06*x^6 + C05*x^5 + C04*x^4 + C03*x^3 + C02*x^2

   *              C01*x   + C00;

   */

  vector float r, r1, r2, r_hi, r_lo;

  vector float xabs, x2, x4, x6;

  vector float p, p_hi, p_lo;

  vector float q, q_hi, q_lo;

  vector float pi_over_2 = spu_splats(1.5707963267949f);

  vector float pi_over_4 = spu_splats(0.7853981633974f);

  vector unsigned int msb = spu_splats(0x80000000);

  x2 = spu_mul(x, x);

  x4 = spu_mul(x2, x2);

  x6 = spu_mul(x4, x2);

  xabs = spu_andc(x, (vector float)msb);

  /* Compute arc-sin for values in the range [0, PI/4]

   */

  p_hi = spu_madd(spu_splats(0.0000347933107596021167570f), x2,

                  spu_splats(0.000791534994289814532176f));

  p_hi = spu_madd(p_hi, x2, spu_splats(-0.0400555345006794114027f));

  p_lo = spu_madd(spu_splats(0.201212532134862925881f), x2,

                  spu_splats(-0.325565818622400915405f));

  p_lo = spu_madd(p_lo, x2, spu_splats(0.166666666666666657415f));

  p = spu_madd(p_hi, x6, p_lo);

  q_hi = spu_madd(spu_splats(0.0770381505559019352791f), x2,

                  spu_splats(-0.688283971605453293030f));

  q_hi = spu_madd(q_hi, x2, spu_splats(2.02094576023350569471f));

  q_lo = spu_madd(spu_splats(-2.40339491173441421878f), x2,

                  spu_splats(1.0f));

  q = spu_madd(q_hi, x4, q_lo);

  r1 = spu_madd(_divf4(p, q), spu_mul(xabs, x2), xabs);

  /* Compute arc-sin for values in the range [PI/4, 1]

   */

  r_hi = spu_madd(spu_splats(-0.0012624911f), xabs,

                  spu_splats(0.0066700901f));

  r_hi = spu_madd(r_hi, xabs, spu_splats(-0.0170881256f));

  r_hi = spu_madd(r_hi, xabs, spu_splats(0.0308918810f));

  r_lo = spu_madd(spu_splats(-0.0501743046f), xabs,

                  spu_splats(0.0889789874f));

  r_lo = spu_madd(r_lo, xabs, spu_splats(-0.2145988016f));

  r_lo = spu_madd(r_lo, xabs, pi_over_2);

  r = spu_madd(r_hi, x4, r_lo);

  r2 = spu_nmsub(r, _sqrtf4(spu_sub(spu_splats(1.0f), xabs)),

                 pi_over_2);

  /* Select the result depending upon the input value. Correct the

   * sign of the result.

   */

  return (spu_sel(spu_sel(r1, r2, spu_cmpgt(xabs, pi_over_4)),

                  x, msb));

}

#endif /* _ASINF4_H_ */

#endif /* __SPU__ */