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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [machine/] [spu/] [headers/] [expf4.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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/* --------------------------------------------------------------  */
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/* PROLOG END TAG zYx                                              */
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#ifdef __SPU__
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#ifndef _EXPF4_H_
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#define _EXPF4_H_       1
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#include "floorf4.h"
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#include "ldexpf4.h"
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/*
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 * FUNCTION
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 *      vector float _expf4(vector float x)
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 *
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 * DESCRIPTION
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 *      The _expf4 function computes e raised to the input x for
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 *      each of the element of the float vector.
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 *
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 */
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static __inline vector float _expf4(vector float x)
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{
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  //  log2(e)
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  vec_float4 log2e = spu_splats(1.4426950408889634074f);
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  // Extra precision for the ln2 multiply
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  vec_float4 ln2_hi = spu_splats(0.693359375f);
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  vec_float4 ln2_lo = spu_splats(-2.12194440E-4f);
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  // Coefficents for the Taylor series
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  vec_float4 f02 = spu_splats(5.0000000000000000E-1f); // 1/2!
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  vec_float4 f03 = spu_splats(1.6666666666666667E-1f); // 1/3!
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  vec_float4 f04 = spu_splats(4.1666666666666667E-2f); // 1/4!
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  vec_float4 f05 = spu_splats(8.3333333333333333E-3f); // 1/5!
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  vec_float4 f06 = spu_splats(1.3888888888888889E-3f); // 1/6!
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  vec_float4 f07 = spu_splats(1.9841269841269841E-4f); // 1/7!
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  //  Range reduce input, so that:
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  //  e^x = e^z * 2^n
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  //  e^x = e^z * e^(n * ln(2))
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  //  e^x = e^(z + (n * ln(2)))
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  vec_int4 n;  // exponent of reduction
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  vec_float4 q;  // range reduced result
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  vec_float4 z;
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  vec_float4 r;
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  z = spu_madd(x,log2e,spu_splats(0.5f));
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  z = _floorf4(z);
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  r = spu_nmsub(z,ln2_hi,x);
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  r = spu_nmsub(z,ln2_lo,r);
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  n = spu_convts(z,0);
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  z = spu_mul(r,r);
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  //  Use Horner's method on the Taylor series
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  q = spu_madd(r,f07,f06);
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  q = spu_madd(q,r,f05);
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  q = spu_madd(q,r,f04);
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  q = spu_madd(q,r,f03);
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  q = spu_madd(q,r,f02);
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  q = spu_madd(q,z,r);
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  q = spu_add(q,spu_splats(1.0f));
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  //  Adjust the result by the range reduction
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  r  = _ldexpf4( q, n );
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  return(r);
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}
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#endif /* _EXPF4_H_ */
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#endif /* __SPU__ */
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