xref: /illumos-gate/usr/src/lib/libc/port/fp/pack_float.c (revision 1da57d55)

/*
 * 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.
 */

#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;
}