/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma weak nearbyintf = __nearbyintf

#include "libm.h"
#include <fenv.h>

float
__nearbyintf(float x) {
        union {
                unsigned i;
                float f;
        } xx;
        unsigned hx, sx, i, frac;
        int rm;

        xx.f = x;
        sx = xx.i & 0x80000000;
        hx = xx.i & ~0x80000000;

        /* handle trivial cases */
        if (hx >= 0x4b000000) { /* x is nan, inf, or already integral */
                if (hx > 0x7f800000)    /* x is nan */
                        return (x * x);         /* + -> * for Cheetah */
                return (x);
        } else if (hx == 0)             /* x is zero */
                return (x);

        /* get the rounding mode */
        rm = fegetround();

        /* flip the sense of directed roundings if x is negative */
        if (sx && (rm == FE_UPWARD || rm == FE_DOWNWARD))
                rm = (FE_UPWARD + FE_DOWNWARD) - rm;

        /* handle |x| < 1 */
        if (hx < 0x3f800000) {
                if (rm == FE_UPWARD || (rm == FE_TONEAREST && hx > 0x3f000000))
                        xx.i = sx | 0x3f800000;
                else
                        xx.i = sx;
                return (xx.f);
        }

        /* round x at the integer bit */
        i = 1 << (0x96 - (hx >> 23));
        frac = hx & (i - 1);
        if (!frac)
                return (x);

        hx &= ~(i - 1);
        if (rm == FE_UPWARD || (rm == FE_TONEAREST && (frac > (i >> 1) ||
                ((frac == (i >> 1)) && (hx & i)))))
                xx.i = sx | (hx + i);
        else
                xx.i = sx | hx;
        return (xx.f);
}

#if 0

/*
 * Alternate implementations for SPARC, x86, using fp ops.  These may
 * be faster depending on how expensive saving and restoring the fp
 * modes and status flags is.
 */

#include "libm.h"
#include "fma.h"

#if defined(__sparc)

float
__nearbyintf(float x) {
        union {
                unsigned i;
                float f;
        } xx, yy;
        float z;
        unsigned hx, sx, fsr, oldfsr;
        int rm;

        xx.f = x;
        sx = xx.i & 0x80000000;
        hx = xx.i & ~0x80000000;

        /* handle trivial cases */
        if (hx >= 0x4b000000)   /* x is nan, inf, or already integral */
                return (x + 0.0f);
        else if (hx == 0)       /* x is zero */
                return (x);

        /* save the fsr */
        __fenv_getfsr(&oldfsr);

        /* handle |x| < 1 */
        if (hx < 0x3f800000) {
                /* flip the sense of directed roundings if x is negative */
                rm = oldfsr >> 30;
                if (sx)
                        rm ^= rm >> 1;
                if (rm == FSR_RP || (rm == FSR_RN && hx > 0x3f000000))
                        xx.i = sx | 0x3f800000;
                else
                        xx.i = sx;
                return (xx.f);
        }

        /* clear the inexact trap */
        fsr = oldfsr & ~FSR_NXM;
        __fenv_setfsr(&fsr);

        /* round x at the integer bit */
        yy.i = sx | 0x4b000000;
        z = (x + yy.f) - yy.f;

        /* restore the old fsr */
        __fenv_setfsr(&oldfsr);

        return (z);
}

#elif defined(__x86)

/* inline template */
extern long double frndint(long double);

float
__nearbyintf(float x) {
        long double z;
        unsigned oldcwsw, cwsw;

        /* save the control and status words, mask the inexact exception */
        __fenv_getcwsw(&oldcwsw);
        cwsw = oldcwsw | 0x00200000;
        __fenv_setcwsw(&cwsw);

        z = frndint((long double) x);

        /*
         * restore the control and status words, preserving all but the
         * inexact flag
         */
        __fenv_getcwsw(&cwsw);
        oldcwsw |= (cwsw & 0x1f);
        __fenv_setcwsw(&oldcwsw);

        /* note: the value of z is representable in single precision */
        return (z);
}

#else
#error Unknown architecture
#endif

#endif