Retro68/gcc/newlib/libm/machine/spu/headers/erfd2.h
2012-03-27 01:51:53 +02:00

124 lines
4.5 KiB
C

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/* PROLOG END TAG zYx */
#ifdef __SPU__
#ifndef _ERFD2_H_
#define _ERFD2_H_ 1
#include <spu_intrinsics.h>
#include "expd2.h"
#include "recipd2.h"
#include "divd2.h"
#include "erf_utils.h"
/*
* FUNCTION
* vector double _erfd2(vector double x)
*
* DESCRIPTION
* The erfd2 function computes the error function of each element of x.
*
* C99 Special Cases:
* - erf(+0) returns +0
* - erf(-0) returns -0
* - erf(+infinite) returns +1
* - erf(-infinite) returns -1
*
* Other Cases:
* - erf(Nan) returns Nan
*
*/
static __inline vector double _erfd2(vector double x)
{
vec_uchar16 dup_even = ((vec_uchar16) { 0,1,2,3, 0,1,2,3, 8, 9,10,11, 8, 9,10,11 });
vec_double2 onehalfd = spu_splats(0.5);
vec_double2 oned = spu_splats(1.0);
vec_double2 sign_mask = spu_splats(-0.0);
/* This is where we switch from Taylor Series to Continued Fraction approximation */
vec_float4 approx_point = spu_splats(1.77f);
vec_double2 xabs, xsqu, xsign;
vec_double2 tresult, presult, result;
xsign = spu_and(x, sign_mask);
xabs = spu_andc(x, sign_mask);
xsqu = spu_mul(x, x);
/*
* Taylor Series Expansion near Zero
*/
TAYLOR_ERF(xabs, xsqu, tresult);
/*
* Continued Fraction Approximation of Erfc().
* erf = 1 - erfc
*/
CONTFRAC_ERFC(xabs, xsqu, presult);
presult = spu_sub(oned, presult);
/*
* Select the appropriate approximation.
*/
vec_float4 xf = spu_roundtf(xabs);
xf = spu_shuffle(xf, xf, dup_even);
result = spu_sel(tresult, presult, (vec_ullong2)spu_cmpgt(xf, approx_point));
/*
* Special cases/errors.
*/
/* x = +/- infinite, return +/-1 */
/* x = nan, return x */
result = spu_sel(result, oned, spu_testsv(x, SPU_SV_NEG_INFINITY | SPU_SV_POS_INFINITY));
result = spu_sel(result, x, spu_testsv(x, SPU_SV_NEG_DENORM | SPU_SV_POS_DENORM));
/*
* Preserve sign in result, since erf(-x) = -erf(x)
*/
result = spu_or(result, xsign);
return result;
}
#endif /* _ERFD2_H_ */
#endif /* __SPU__ */