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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [machine/] [spu/] [headers/] [atanf4.h] - Blame information for rev 207

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1 207 jeremybenn
/* --------------------------------------------------------------  */
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/* (C)Copyright 2001,2008,                                         */
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/* International Business Machines Corporation,                    */
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/* Sony Computer Entertainment, Incorporated,                      */
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/* Toshiba Corporation,                                            */
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/* without modification, are permitted provided that the           */
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/* following conditions are met:                                   */
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/*   notice, this list of conditions and the following disclaimer. */
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/*   contributors may be used to endorse or promote products       */
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/*   derived from this software without specific prior written     */
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/* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND          */
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/* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.              */
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/* --------------------------------------------------------------  */
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/* PROLOG END TAG zYx                                              */
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#ifdef __SPU__
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#ifndef _ATANF4_H_
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#define _ATANF4_H_      1
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#include <spu_intrinsics.h>
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#include "simdmath.h"
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#include "recipf4.h"
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/*
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 * FUNCTION
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 *      vector float _atanf4(vector float x)
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 *
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 * DESCRIPTION
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 *      The _atanf4 function computes the arc tangent of a vector of values x;
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 *      that is the values whose tangent is x.
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 *
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 *      The _atanf4 function returns the arc tangents in radians and the value
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 *      is mathematically defined to be in the range -PI/2 to PI/2.
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 *
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 *      The arc tangent function is computed using a polynomial approximation
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 *      (B. Carlson, M. Goldstein, Los Alamos Scientific Laboratory, 1955).
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 *                __8__
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 *                \
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 *                 \
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 *      atan(x) =  /    Ci*x^(2*i+1)
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 *                /____
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 *                 i=0
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 *
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 *      for x in the range -1 to 1. The remaining regions are defined to be:
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 *
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 *      [1, infinity]   :  PI/2 + atanf(-1/x)
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 *      [-infinity, -1] : -PI/2 + atanf(-1/x)
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 *
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 */
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static __inline vector float _atanf4(vector float x)
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{
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  vector float bias;
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  vector float x2, x3, x4, x8, x9;
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  vector float hi, lo;
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  vector float result;
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  vector float inv_x;
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  vector unsigned int sign;
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  vector unsigned int select;
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  sign = spu_sl(spu_rlmask((vector unsigned int)x, -31), 31);
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  inv_x = _recipf4(x);
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  inv_x = (vector float)spu_xor((vector unsigned int)inv_x, spu_splats(0x80000000));
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  select = (vector unsigned int)spu_cmpabsgt(x, spu_splats(1.0f));
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  bias = (vector float)spu_or(sign, (vector unsigned int)(spu_splats((float)SM_PI_2)));
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  bias = (vector float)spu_and((vector unsigned int)bias, select);
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  x = spu_sel(x, inv_x, select);
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  /* Instruction counts can be reduced if the polynomial was
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   * computed entirely from nested (dependent) fma's. However,
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   * to reduce the number of pipeline stalls, the polygon is evaluated
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   * in two halves(hi and lo).
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   */
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  bias = spu_add(bias, x);
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  x2 = spu_mul(x, x);
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  x3 = spu_mul(x2, x);
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  x4 = spu_mul(x2, x2);
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  x8 = spu_mul(x4, x4);
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  x9 = spu_mul(x8, x);
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  hi = spu_madd(spu_splats(0.0028662257f), x2, spu_splats(-0.0161657367f));
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  hi = spu_madd(hi, x2, spu_splats(0.0429096138f));
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  hi = spu_madd(hi, x2, spu_splats(-0.0752896400f));
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  hi = spu_madd(hi, x2, spu_splats(0.1065626393f));
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  lo = spu_madd(spu_splats(-0.1420889944f), x2, spu_splats(0.1999355085f));
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  lo = spu_madd(lo, x2, spu_splats(-0.3333314528f));
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  lo = spu_madd(lo, x3, bias);
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  result = spu_madd(hi, x9, lo);
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  return (result);
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}
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#endif /* _ATANF4_H_ */
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#endif /* __SPU__ */
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