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/* PROLOG END TAG zYx                                              */
#ifdef __SPU__
#ifndef _SQRTF4_H_
#define _SQRTF4_H_ 1

#include <spu_intrinsics.h>

/*
 * FUNCTION
 *      vector float _sqrtf4(vector float in)
 *
 * DESCRIPTION
 *      The _sqrtf4 function computes the square root of the vector input "in"
 *and returns the result.
 *
 */
static __inline vector float
_sqrtf4(vector float in)
{
    vec_uint4  exp, valid;
    vec_uint4  mask = spu_splats((unsigned int)0xFF000000);
    vec_uint4  half = spu_splats((unsigned int)0x00800000);
    vec_float4 one = spu_splats(1.0f);
    vec_float4 three = spu_splats(3.0f);
    vec_float4 x, y0, y1, y1_n1, y1_p1, y1_p2, y1_p3;
    vec_float4 mant, err, err_p1, err_p2, err_p3;
    vec_float4 out;

    /* Compute the mantissa of the result seperately from
     * the exponent to assure complete accuracy over the allowable
     * input range. The mantissa is computed for inputs in the
     * range [0.5, 2.0).
     */
    x = spu_sel(in, one, mask);
    y0 = spu_rsqrte(x);

    /* Perform one iteration of the Newton-Raphsom method in single precision
     * arithmetic.
     */
    y1 = spu_mul(spu_nmsub(x, spu_mul(y0, y0), three),
                 spu_mul(y0, (vec_float4)(spu_sub((vec_uint4)(x), half))));

    /* Correct the result for possible error. The range of error is -3 to +1.
     * Identify the extent of the error and correct for it.
     */
    y1_p3 = (vec_float4)spu_add((vec_uint4)(y1), 3);
    y1_p2 = (vec_float4)spu_add((vec_uint4)(y1), 2);
    y1_p1 = (vec_float4)spu_add((vec_uint4)(y1), 1);
    y1_n1 = (vec_float4)spu_add((vec_uint4)(y1), -1);

    err = spu_nmsub(y1, y1, x);
    err_p1 = spu_nmsub(y1_p1, y1_p1, x);
    err_p2 = spu_nmsub(y1_p2, y1_p2, x);
    err_p3 = spu_nmsub(y1_p3, y1_p3, x);

    mant = spu_sel(y1_n1, y1, spu_cmpgt((vec_int4)(err), -1));
    mant = spu_sel(mant, y1_p1, spu_cmpgt((vec_int4)(err_p1), -1));
    mant = spu_sel(mant, y1_p2, spu_cmpgt((vec_int4)(err_p2), -1));
    mant = spu_sel(mant, y1_p3, spu_cmpgt((vec_int4)(err_p3), -1));

    /* Compute the expected exponent. If the exponent is zero or the input is
     * negative, then set the result to zero.
     */
    exp = spu_rlmask(spu_add((vec_uint4)(in), (vec_uint4)(one)), -1);

    valid = spu_cmpgt(spu_and((vec_int4)(in), (vec_int4)(mask)), 0);

    /* Merge the computed exponent and mantissa.
     */
    out = spu_and(spu_sel(mant, (vec_float4)(exp), spu_splats(0xFF800000)), (vec_float4)(valid));

    return (out);
}

#endif /* _SQRTF4_H_ */
#endif /* __SPU__ */
