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/* PROLOG END TAG zYx                                              */
#ifdef __SPU__
#ifndef _RECIPF4_H_
#define _RECIPF4_H_ 1

#include <spu_intrinsics.h>

/*
 * FUNCTION
 *	vector float _recipf4(vector float value)
 *
 * DESCRIPTION
 * 	The _recipf4 function inverts the vector "value" and returns the
 *      result.
 *
 */
static __inline vector float
_recipf4(vector float a)
{
    /* This function has been designed to provide a
     * full function operation that presisely computes
     * the reciprocal for the entire range of extended
     * single precision input <a>. This includes:
     *
     * 1) Computing the reciprocal to full single precision
     *    floating point accuracy.
     * 2) Round the result consistently with the rounding
     *    mode of the processor - truncated toward zero.
     * 3) Underflow and overflow results are clamped to
     *    Smin and Smax and flagged with the appropriate
     *    UNF or OVF exception in the FPSCR.
     * 4) Divide By Zero (DBZ) exception is produced when
     *    the input <a> has a zero exponent. A reciprocal
     *    of correctly signed Smax is produced.
     * 5) Resulting denorm reciprocal will be coerced to +0.
     * 6) If a non-compliant IEEE result is produced, the
     *    a DIFF exception is generated.
     */
    vector float        err, x0, x1;
    vector float        mult;
    vector float        mant_a;
    vector float        one = spu_splats(1.0f);
    vector unsigned int exp, exp_a;
    vector unsigned int exp_mask = (vec_uint4)spu_splats(0x7F800000);

    /* If a has a zero exponent, then set the divide by zero
     * (DBZ) exception flag. The estimate result is discarded.
     */
    (void)si_frest((qword)(a));

    /* For computing the reciprocal, force the value
     * into the range (1.0 <= 0 < 2.0).
     */
    mant_a = spu_sel(a, one, exp_mask);

    /* Compute the reciprocal using the reciprocal estimate
     * followed by one iteration of the Newton-Raphson.
     * Due to truncation error, the quotient result may be low
     * by 1 ulp (unit of least position). Conditionally add one
     * if the estimate is too small.
     */
    x0 = spu_re(mant_a);
    x0 = spu_madd(spu_nmsub(mant_a, x0, one), x0, x0);

    x1 = (vector float)(spu_add((vector unsigned int)(x0), 1));
    err = spu_nmsub(mant_a, x1, one);

    x1 = spu_sel(x0, x1, spu_cmpgt((vector signed int)(err), -1));

    /* Compute the reciprocal's expected exponent. If the exponent
     * is out of range, then force the resulting exponent to 0.
     * (127 with the bias). We correct for the out of range
     * values by computing a multiplier (mult) that will force the
     * result to the correct out of range value and set the
     * correct exception flag (UNF, OVF, or neither). The multiplier
     * is also conditioned to generate correctly signed Smax if the
     * inoput <a> is a denorm or zero.
     */
    exp_a = spu_and((vector unsigned int)a, exp_mask);
    exp = spu_add(spu_sub(spu_splats((unsigned int)0x7F000000), exp_a), spu_cmpabsgt(mant_a, one));

    /* The default multiplier is 1.0. If an underflow is detected (ie,
     * either the dividend <a> is a denorm/zero, or the computed exponent is
     * less than or equal to a biased 0), force the multiplier to 0.0.
     */
    mult = spu_and(one, (vector float)spu_cmpgt((vector signed int)(exp), 0));

    /* Force the multiplier to positive Smax (0x7FFFFFFF) and the biased exponent
     * to 127, if the divisor is denorm/zero or the computed biased exponent is
     * greater than 255.
     */
    mult = spu_or(mult, (vector float)spu_rlmask(spu_cmpeq(exp_a, 0), -1));

    /* Insert the exponent into the result and perform the
     * final multiplication.
     */
    x1 = spu_sel(x1, (vector float)exp, exp_mask);
    x1 = spu_mul(x1, mult);

    return (x1);
}

#endif /* _RECIPF4_H_ */
#endif /* __SPU__ */
