port/fp/pack_float.c

	pack_float.c revision 7257d1b4d25bfac0c802847390e98a464fd787ac
/*
 * 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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include "lint.h"
#include "base_conversion.h"

static void
__fp_rightshift(unpacked *pu, int n)

/* Right shift significand sticky by n bits.  */

{
    int     i;

    if (n >= (32 * UNPACKED_SIZE)) {    /* drastic */
        for (i = 0; (pu->significand[i] == 0) && (i < UNPACKED_SIZE);
                i++);
        if (i >= UNPACKED_SIZE) {
            pu->fpclass = fp_zero;
            return;
        } else {
            for (i = 0; i < (UNPACKED_SIZE - 1); i++)
                pu->significand[i] = 0;
            pu->significand[UNPACKED_SIZE - 1] = 1;
            return;
        }
    }
    while (n >= 32) {   /* big shift */
        if (pu->significand[UNPACKED_SIZE - 1] != 0)
            pu->significand[UNPACKED_SIZE - 2] |= 1;
        for (i = UNPACKED_SIZE - 2; i >= 0; i--)
            pu->significand[i + 1] = pu->significand[i];
        pu->significand[0] = 0;
        n -= 32;
    }
    if (n >= 1) {       /* small shift */
        unsigned int   high, low, shiftout = 0;
        for (i = 0; i < UNPACKED_SIZE; i++) {
            high = pu->significand[i] >> n;
            low = pu->significand[i] << (32 - n);
            pu->significand[i] = shiftout | high;
            shiftout = low;
        }
        if (shiftout != 0)
            pu->significand[UNPACKED_SIZE - 1] |= 1;
    }
}

static int
overflow_to_infinity(int sign, enum fp_direction_type rd)

/* Returns 1 if overflow should go to infinity, 0 if to max finite. */

{
    int     inf;

    switch (rd) {
    case fp_nearest:
        inf = 1;
        break;
    case fp_tozero:
        inf = 0;
        break;
    case fp_positive:
        inf = !sign;
        break;
    case fp_negative:
        inf = sign;
        break;
    }
    return (inf);
}

static void
round(unpacked *pu, int roundword, enum fp_direction_type rd, int *ex)
/*
 * Round according to current rounding mode. pu must be shifted to so that
 * the roundbit is pu->significand[roundword] & 0x80000000
 */
{
    int     increment;  /* boolean to indicate round up */
    int     is;
    unsigned    msw;        /* msw before increment */

    for (is = (roundword + 1); is < UNPACKED_SIZE; is++)
        if (pu->significand[is] != 0) {
        /* Condense extra bits into sticky bottom of roundword. */
            pu->significand[roundword] |= 1;
            break;
        }
    if (pu->significand[roundword] == 0)
        return;
    *ex |= (1 << fp_inexact);
    switch (rd) {
    case fp_nearest:
        increment = pu->significand[roundword] >= 0x80000000;
        break;
    case fp_tozero:
        increment = 0;
        break;
    case fp_positive:
        increment = (pu->sign == 0) & (pu->significand[roundword] != 0);
        break;
    case fp_negative:
        increment = (pu->sign != 0) & (pu->significand[roundword] != 0);
        break;
    }
    if (increment) {
        msw = pu->significand[0];   /* save msw before round */
        is = roundword;
        do {
            is--;
            pu->significand[is]++;
        }
        while ((pu->significand[is] == 0) && (is > 0));
        if (pu->significand[0] < msw) { /* rounding carried out */
            pu->exponent++;
            pu->significand[0] = 0x80000000;
        }
    }
    if ((rd == fp_nearest) &&
        (pu->significand[roundword] == 0x80000000)) {
        /* ambiguous case */
        pu->significand[roundword - 1] &= ~1; /* force round to even */
    }
}

void
__pack_single(unpacked *pu, single *px, enum fp_direction_type rd,
    fp_exception_field_type *ex)
{
    single_equivalence kluge;
    int     e;

    e = 0;
    kluge.f.msw.sign = pu->sign;
    switch (pu->fpclass) {
    case fp_zero:
        kluge.f.msw.exponent = 0;
        kluge.f.msw.significand = 0;
        break;
    case fp_infinity:
infinity:
        kluge.f.msw.exponent = 0xff;
        kluge.f.msw.significand = 0;
        break;
    case fp_quiet:
        kluge.f.msw.exponent = 0xff;
        kluge.f.msw.significand = 0x400000 |
            (0x3fffff & (pu->significand[0] >> 8));
        break;
    case fp_normal:
        __fp_rightshift(pu, 8);
        pu->exponent += SINGLE_BIAS;
        if (pu->exponent <= 0) {
            kluge.f.msw.exponent = 0;
            __fp_rightshift(pu, 1 - pu->exponent);
            round(pu, 1, rd, &e);
            if (pu->significand[0] == 0x800000) {
                /* rounded back up to normal */
                kluge.f.msw.exponent = 1;
                kluge.f.msw.significand = 0;
                e |= (1 << fp_underflow);
                goto ret;
            }
            if (e & (1 << fp_inexact))
                e |= (1 << fp_underflow);
            kluge.f.msw.significand = 0x7fffff & pu->significand[0];
            goto ret;
        }
        round(pu, 1, rd, &e);
        if (pu->significand[0] == 0x1000000) {  /* rounding overflow */
            pu->significand[0] = 0x800000;
            pu->exponent += 1;
        }
        if (pu->exponent >= 0xff) {
            e |= (1 << fp_overflow) | (1 << fp_inexact);
            if (overflow_to_infinity(pu->sign, rd))
                goto infinity;
            kluge.f.msw.exponent = 0xfe;
            kluge.f.msw.significand = 0x7fffff;
            goto ret;
        }
        kluge.f.msw.exponent = pu->exponent;
        kluge.f.msw.significand = 0x7fffff & pu->significand[0];
    }
ret:
    *px = kluge.x;
    *ex = (fp_exception_field_type)e;
}

void
__pack_double(unpacked *pu, double *px, enum fp_direction_type rd,
    fp_exception_field_type *ex)
{
    double_equivalence kluge;
    int     e;

    e = 0;
    kluge.f.msw.sign = pu->sign;
    switch (pu->fpclass) {
    case fp_zero:
        kluge.f.msw.exponent = 0;
        kluge.f.msw.significand = 0;
        kluge.f.significand2 = 0;
        break;
    case fp_infinity:
infinity:
        kluge.f.msw.exponent = 0x7ff;
        kluge.f.msw.significand = 0;
        kluge.f.significand2 = 0;
        break;
    case fp_quiet:
        kluge.f.msw.exponent = 0x7ff;
        __fp_rightshift(pu, 11);
        kluge.f.msw.significand = 0x80000 |
            (0x7ffff & pu->significand[0]);
        kluge.f.significand2 = pu->significand[1];
        break;
    case fp_normal:
        __fp_rightshift(pu, 11);
        pu->exponent += DOUBLE_BIAS;
        if (pu->exponent <= 0) {    /* underflow */
            __fp_rightshift(pu, 1 - pu->exponent);
            round(pu, 2, rd, &e);
            if (pu->significand[0] == 0x100000) {
                /* rounded back up to normal */
                kluge.f.msw.exponent = 1;
                kluge.f.msw.significand = 0;
                kluge.f.significand2 = 0;
                e |= (1 << fp_underflow);
                goto ret;
            }
            if (e & (1 << fp_inexact))
                e |= (1 << fp_underflow);
            kluge.f.msw.exponent = 0;
            kluge.f.msw.significand = 0xfffff & pu->significand[0];
            kluge.f.significand2 = pu->significand[1];
            goto ret;
        }
        round(pu, 2, rd, &e);
        if (pu->significand[0] == 0x200000) {   /* rounding overflow */
            pu->significand[0] = 0x100000;
            pu->exponent += 1;
        }
        if (pu->exponent >= 0x7ff) {    /* overflow */
            e |= (1 << fp_overflow) | (1 << fp_inexact);
            if (overflow_to_infinity(pu->sign, rd))
                goto infinity;
            kluge.f.msw.exponent = 0x7fe;
            kluge.f.msw.significand = 0xfffff;
            kluge.f.significand2 = 0xffffffff;
            goto ret;
        }
        kluge.f.msw.exponent = pu->exponent;
        kluge.f.msw.significand = 0xfffff & pu->significand[0];
        kluge.f.significand2 = pu->significand[1];
        break;
    }
ret:
    *px = kluge.x;
    *ex = (fp_exception_field_type)e;
}

void
__pack_extended(unpacked *pu, extended *px, enum fp_direction_type rd,
    fp_exception_field_type *ex)
{
    extended_equivalence kluge;
    int     e;

    e = 0;
    kluge.f.msw.sign = pu->sign;
    switch (pu->fpclass) {
    case fp_zero:
        kluge.f.msw.exponent = 0;
        kluge.f.significand = 0;
        kluge.f.significand2 = 0;
        break;
    case fp_infinity:
infinity:
        kluge.f.msw.exponent = 0x7fff;
        kluge.f.significand = 0x80000000;
        kluge.f.significand2 = 0;
        break;
    case fp_quiet:
        kluge.f.msw.exponent = 0x7fff;
        kluge.f.significand = 0x40000000 | pu->significand[0];
        kluge.f.significand2 = pu->significand[1];
        break;
    case fp_normal:
        pu->exponent += EXTENDED_BIAS;
        if (pu->exponent <= 0) {    /* underflow */
            __fp_rightshift(pu, 1 - pu->exponent);
            round(pu, 2, rd, &e);
            if (pu->significand[0] == 0x80000000u) {
                /* rounded back up to normal */
                kluge.f.msw.exponent = 1;
                kluge.f.significand = 0x80000000u;
                kluge.f.significand2 = 0;
                e |= (1 << fp_underflow);
                goto ret;
            }
            if (e & (1 << fp_inexact))
                e |= (1 << fp_underflow);
            kluge.f.msw.exponent = 0;
            kluge.f.significand = pu->significand[0];
            kluge.f.significand2 = pu->significand[1];
            goto ret;
        }
        round(pu, 2, rd, &e);
        if (pu->exponent >= 0x7fff) {   /* overflow */
            e |= (1 << fp_overflow) | (1 << fp_inexact);
            if (overflow_to_infinity(pu->sign, rd))
                goto infinity;
            kluge.f.msw.exponent = 0x7ffe;
            kluge.f.significand = 0xffffffff;
            kluge.f.significand2 = 0xffffffff;
            goto ret;
        }
        kluge.f.msw.exponent = pu->exponent;
        kluge.f.significand = pu->significand[0];
        kluge.f.significand2 = pu->significand[1];
        break;
    }
ret:
    (*px)[0] = kluge.x[0];
    (*px)[1] = kluge.x[1];
    (*px)[2] = kluge.x[2];
    *ex = (fp_exception_field_type)e;
}

void
__pack_quadruple(unpacked *pu, quadruple *px, enum fp_direction_type rd,
    fp_exception_field_type *ex)
{
    quadruple_equivalence kluge;
    int     e;

    e = 0;
    kluge.f.msw.sign = pu->sign;
    switch (pu->fpclass) {
    case fp_zero:
        kluge.f.msw.exponent = 0;
        kluge.f.msw.significand = 0;
        kluge.f.significand2 = 0;
        kluge.f.significand3 = 0;
        kluge.f.significand4 = 0;
        break;
    case fp_infinity:
infinity:
        kluge.f.msw.exponent = 0x7fff;
        kluge.f.msw.significand = 0;
        kluge.f.significand2 = 0;
        kluge.f.significand3 = 0;
        kluge.f.significand4 = 0;
        break;
    case fp_quiet:
        kluge.f.msw.exponent = 0x7fff;
        __fp_rightshift(pu, 15);
        kluge.f.msw.significand = 0x8000 |
            (0xffff & pu->significand[0]);
        kluge.f.significand2 = pu->significand[1];
        kluge.f.significand3 = pu->significand[2];
        kluge.f.significand4 = pu->significand[3];
        break;
    case fp_normal:
        __fp_rightshift(pu, 15);
        pu->exponent += QUAD_BIAS;
        if (pu->exponent <= 0) {    /* underflow */
            __fp_rightshift(pu, 1 - pu->exponent);
            round(pu, 4, rd, &e);
            if (pu->significand[0] == 0x10000) {
                /* rounded back up to normal */
                kluge.f.msw.exponent = 1;
                kluge.f.msw.significand = 0;
                kluge.f.significand2 = 0;
                kluge.f.significand3 = 0;
                kluge.f.significand4 = 0;
                e |= (1 << fp_underflow);
                goto ret;
            }
            if (e & (1 << fp_inexact))
                e |= (1 << fp_underflow);
            kluge.f.msw.exponent = 0;
            kluge.f.msw.significand = 0xffff & pu->significand[0];
            kluge.f.significand2 = pu->significand[1];
            kluge.f.significand3 = pu->significand[2];
            kluge.f.significand4 = pu->significand[3];
            goto ret;
        }
        round(pu, 4, rd, &e);
        if (pu->significand[0] == 0x20000) {    /* rounding overflow */
            pu->significand[0] = 0x10000;
            pu->exponent += 1;
        }
        if (pu->exponent >= 0x7fff) {   /* overflow */
            e |= (1 << fp_overflow) | (1 << fp_inexact);
            if (overflow_to_infinity(pu->sign, rd))
                goto infinity;
            kluge.f.msw.exponent = 0x7ffe;
            kluge.f.msw.significand = 0xffff;
            kluge.f.significand2 = 0xffffffff;
            kluge.f.significand3 = 0xffffffff;
            kluge.f.significand4 = 0xffffffff;
            goto ret;
        }
        kluge.f.msw.exponent = pu->exponent;
        kluge.f.msw.significand = pu->significand[0] & 0xffff;
        kluge.f.significand2 = pu->significand[1];
        kluge.f.significand3 = pu->significand[2];
        kluge.f.significand4 = pu->significand[3];
        break;
    }
ret:
    *px = kluge.x;
    *ex = (fp_exception_field_type)e;
}