common/m9x/nearbyint.c

25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis/*
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25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis/*
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis/*
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Use is subject to license terms.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#pragma weak nearbyint = __nearbyint
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis/*
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * nearbyint(x) returns the nearest fp integer to x in the direction
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * corresponding to the current rounding direction without raising
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * the inexact exception.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis *
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * nearbyint(x) is x unchanged if x is +/-0 or +/-inf.  If x is NaN,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * nearbyint(x) is also NaN.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#include "libm.h"
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#include <fenv.h>
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtisdouble
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis__nearbyint(double x) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    union {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        unsigned i[2];
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        double d;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    } xx;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    unsigned hx, sx, i, frac;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    int rm, j;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    xx.d = x;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    sx = xx.i[HIWORD] & 0x80000000;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    hx = xx.i[HIWORD] & ~0x80000000;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    /* handle trivial cases */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    if (hx >= 0x43300000) { /* x is nan, inf, or already integral */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        if (hx >= 0x7ff00000)   /* x is inf or nan */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            return (hx >= 0x7ff80000 ? x : x + x);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            /* assumes sparc-like QNaN */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#else
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            return (x + x);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#endif
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        return (x);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    } else if ((hx | xx.i[LOWORD]) == 0)    /* x is zero */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        return (x);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    /* get the rounding mode */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    rm = fegetround();
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    /* flip the sense of directed roundings if x is negative */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    if (sx && (rm == FE_UPWARD || rm == FE_DOWNWARD))
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        rm = (FE_UPWARD + FE_DOWNWARD) - rm;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    /* handle |x| < 1 */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    if (hx < 0x3ff00000) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        if (rm == FE_UPWARD || (rm == FE_TONEAREST &&
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            (hx >= 0x3fe00000 && ((hx & 0xfffff) | xx.i[LOWORD]))))
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            xx.i[HIWORD] = sx | 0x3ff00000;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        else
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            xx.i[HIWORD] = sx;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        xx.i[LOWORD] = 0;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        return (xx.d);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    }
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    /* round x at the integer bit */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    j = 0x433 - (hx >> 20);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    if (j >= 32) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        i = 1 << (j - 32);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        frac = ((xx.i[HIWORD] << 1) << (63 - j)) |
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            (xx.i[LOWORD] >> (j - 32));
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        if (xx.i[LOWORD] & (i - 1))
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            frac |= 1;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        if (!frac)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            return (x);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        xx.i[LOWORD] = 0;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        xx.i[HIWORD] &= ~(i - 1);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        if ((rm == FE_UPWARD) || ((rm == FE_TONEAREST) &&
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            ((frac > 0x80000000u) || ((frac == 0x80000000) &&
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            (xx.i[HIWORD] & i)))))
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            xx.i[HIWORD] += i;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    } else {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        i = 1 << j;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        frac = (xx.i[LOWORD] << 1) << (31 - j);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        if (!frac)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            return (x);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        xx.i[LOWORD] &= ~(i - 1);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        if ((rm == FE_UPWARD) || ((rm == FE_TONEAREST) &&
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            (frac > 0x80000000u || ((frac == 0x80000000) &&
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            (xx.i[LOWORD] & i))))) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            xx.i[LOWORD] += i;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis            if (xx.i[LOWORD] == 0)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis                xx.i[HIWORD]++;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis        }
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    }
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis    return (xx.d);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis}