Subversion Repositories openrisc_2011-10-31

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/* PROLOG END TAG zYx                                              */

#ifdef __SPU__

#ifndef _NEXTAFTERD2_H_

#define _NEXTAFTERD2_H_ 1

#include <spu_intrinsics.h>

/*

 * FUNCTION

 *  vector double _nextafterd2(vector double x, vector double y)

 *

 * DESCRIPTION

 *  The nextafterf4 function returns a vector containing the next representable

 *  floating-point number after the element of x, in the direction of the

 *  corresponding element y.

 *

 *  Special Cases:

 *      - nextafter(NaN, y) = NaN

 *      - nextafter(x, NaN) = NaN

 *      - x = largest finite value, y = infinity, result is undefined

 *      - x = largest finite negative value, y = -infinity, result is undefined

 *      - x != y, and result = 0, considered an underflow

 *

 */

static __inline vector double _nextafterd2(vector double x, vector double y)

{

    vec_double2 n1ulp = (vec_double2)spu_splats(0x8000000000000001ull);

    vector unsigned char mov_carry = {0x80,0x80,0x80, 7, 0x80,0x80,0x80,0x80,

                                      0x80,0x80,0x80,15, 0x80,0x80,0x80,0x80};

    vec_double2 zerod = spu_splats(0.0);

    vec_llong2  one   = spu_splats(1ll);

    vec_ullong2 xlt0, xgty, xeqy, xeq0;

    vec_llong2  xllong;

    vec_int4    carry;

    vec_llong2  delta, deltap1;

    vec_double2 result;

    /* Compiler Bug. Replace xtmp/ytmp with x/y when spu_cmpgt(x,y) doesn't change x/y!*/

    volatile vec_double2 xtmp = x;

    volatile vec_double2 ytmp = y;

    /*

     * The idea here is to treat x as a signed long long value, which allows us to

     * add or subtact one to/from it to get the next representable value.

     */

    xeq0 = spu_cmpeq(xtmp, zerod);

    xlt0 = spu_cmpgt(zerod, xtmp);

    xeqy = spu_cmpeq(xtmp, ytmp);

    xgty = spu_cmpgt(xtmp, ytmp);

    /* If x = -0.0, set x = 0.0 */

    x = spu_andc(x, (vec_double2)xeq0);

    xllong = (vec_llong2)x;

    /* Determine value to add to x */

    delta = (vec_llong2)spu_xor(xgty, xlt0);

    //deltap1 = delta + one;

    carry = spu_genc((vec_int4)delta, (vec_int4)one);

    carry = spu_shuffle(carry, carry, mov_carry);

    deltap1 = (vec_llong2)spu_addx((vec_int4)delta, (vec_int4)one, (vec_int4)carry);

    delta = spu_sel(deltap1, delta, (vec_ullong2)delta);

    //xllong = xllong + delta;

    carry = spu_genc((vec_int4)xllong, (vec_int4)delta);

    carry = spu_shuffle(carry, carry, mov_carry);

    xllong = (vec_llong2)spu_addx((vec_int4)xllong, (vec_int4)delta, (vec_int4)carry);

    /* Fix the case of x = 0, and answer should be -1 ulp */

    result = spu_sel((vec_double2)xllong, n1ulp, spu_and((vec_ullong2)delta, xeq0));

    /*

     * Special Cases

     */

    /* x = y */

    result = spu_sel(result, y, xeqy);

    return result;

}

#endif /* _NEXTAFTERD2_H_ */

#endif /* __SPU__ */