coshf4.h

Newlib 嵌入式 C库 标准实现代码

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#ifdef __SPU__
#ifndef _COSHF4_H_
#define _COSHF4_H_ 1

#include <spu_intrinsics.h>

#include "expf4.h"
#include "recipf4.h"


/*
 * FUNCTION
 *	vector float _coshf4(vector float x)
 *
 * DESCRIPTION
 *	The _coshf4 function computes the hyperbolic cosines of a vector of 
 *      angles (expressed in radians) to an accuracy of a single precision 
 *      floating point.
 *
 */
static __inline vector float _coshf4(vector float x)
{
  //  1.0000  (above this number, use sinh(x) = 0.5 * (e^x - e^-x)
  vec_uint4 threshold = (vec_uint4)spu_splats(0x3F800000);

  vec_uint4 sign_mask = (vec_uint4)spu_splats(0x80000000);

  // Coefficents for the Taylor series
  vec_float4 f02 = spu_splats(5.0000000000000000E-1f);  // 1/2!
  vec_float4 f04 = spu_splats(4.1666666666666667E-2f);  // 1/4!
  vec_float4 f06 = spu_splats(1.3888888888888889E-3f);  // 1/6!
  vec_float4 f08 = spu_splats(2.4801587301587302E-5f);  // 1/8!
  vec_float4 f10 = spu_splats(2.7557319223985891E-7f);  // 1/10!
  vec_float4 f12 = spu_splats(2.0876756987868099E-9f);  // 1/12!

  // Perform the calculation as a Taylor series
  vec_float4 result;
  vector float x2 = spu_mul(x,x);
  result = spu_madd(x2,f12,f10);
  result = spu_madd(x2,result,f08);
  result = spu_madd(x2,result,f06);
  result = spu_madd(x2,result,f04);
  result = spu_madd(x2,result,f02);
  result = spu_madd(x2,result,spu_splats(1.0f));


  //  Perform calculation as a function of 0.5 * (e^x - e^-x)
  vec_float4 ex = _expf4(x);
  vec_float4 ex_inv = _recipf4(ex);

  vec_float4 r2= spu_add(ex,ex_inv);
  r2 = spu_mul(r2,f02);  // we can reused f02 here

  vec_uint4 xabs = spu_andc((vec_uint4)x,sign_mask);
  vec_uint4 use_exp = spu_cmpgt(xabs,threshold);

  //  Select either the Taylor or exp version
  result = spu_sel(result,r2,use_exp);

  return result;
}
#endif /* _COSHF4_H_ */
#endif /* __SPU__ */