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/* PROLOG END TAG zYx                                              */

#ifdef __SPU__

#ifndef _HYPOTF4_H_

#define _HYPOTF4_H_     1

#include <spu_intrinsics.h>

#include "sqrtf4.h"

/*

 * FUNCTION

 *  vector float _hypotf4(vector float x, vector float y)

 *

 * DESCRIPTION

 *     The function hypotf4 returns a float vector in which each element is

 *     the square root of the sum of the squares of the corresponding

 *     elements of x and y. In other words, each element is sqrt(x^2 + y^2).

 *

 *     The purpose of this function is to avoid overflow during

 *     intermediate calculations, and therefore it is slower than

 *     simply calcualting sqrt(x^2 + y^2).

 *

 *     This function is performed by factoring out the larger of the 2

 *     input exponents and moving this factor outside of the sqrt calculation.

 *     This will minimize the possibility of over/underflow when the square

 *     of the values are calculated. Think of it as normalizing the larger

 *     input to the range [1,2).

 *

 *

 *  Special Cases:

 *      - hypot(x, +/-0)              returns |x|

 *      - hypot(+/- infinity, y)      returns +infinity

 *      - hypot(+/- infinity, NaN)    returns +infinity

 *

 */

static __inline vector float _hypotf4(vector float x, vector float y)

{

    vector unsigned int emask = spu_splats(0x7F800000u);

    vector unsigned int mmask = spu_splats(0x007FFFFFu);

    vector signed int bias  = spu_splats(0x3F800000);

    vector float inf  = (vec_float4)spu_splats(0x7F800000);

    vector float onef = spu_splats(1.0f);

    vector float sbit = spu_splats(-0.0f);

    vector float max, max_e, max_m;

    vector float min, min_e, min_m;

    vector unsigned int xgty;

    vector float sum;

    vector float result;

    /* Only need absolute values for this function */

    x = spu_andc(x, sbit);

    y = spu_andc(y, sbit);

    xgty = spu_cmpgt(x,y);

    max  = spu_sel(y,x,xgty);

    min  = spu_sel(x,y,xgty);

    /* Extract exponents and mantissas */

    max_e = (vec_float4)spu_and((vec_uint4)max, emask);

    max_m = (vec_float4)spu_and((vec_uint4)max, mmask);

    min_e = (vec_float4)spu_and((vec_uint4)min, emask);

    min_m = (vec_float4)spu_and((vec_uint4)min, mmask);

    /* Adjust the exponent of the smaller of the 2 input values by

     * subtracting max_exp from min_exp.

     */

    vec_int4 min_e_int = spu_sub((vec_int4)min_e, (vec_int4)max_e);

    min_e = (vec_float4)spu_add(min_e_int, bias);

    /* If the new min exponent is too small, just set it to 0. It

     * wouldn't contribute to the final result in either case.

     */

    min_e = spu_sel(min_e, sbit, spu_cmpgt(sbit, min_e));

    /* Combine new exponents with original mantissas */

    max = spu_or(onef, max_m);

    min = spu_or(min_e, min_m);

    sum = _sqrtf4(spu_madd(max, max, spu_mul(min, min)));

    sum = spu_mul(max_e, sum);

    /* Special case: x = +/- infinity */

    result = spu_sel(sum, inf, spu_cmpeq(x, inf));

    return result;

}

#endif /* _HYPOTF4_H_ */

#endif /* __SPU__ */