Subversion Repositories HelenOS-historic

/*

 * Copyright (C) 2005 Josef Cejka

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in the

 *   documentation and/or other materials provided with the distribution.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include<sftypes.h>

#include<common.h>

/* Table for fast leading zeroes counting */

char zeroTable[256] = {

	8, 7, 7, 6, 6, 6, 6, 4, 4, 4, 4, 4, 4, 4, 4, \

	3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, \

	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \

	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \

	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \

	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \

	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \

	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

};

/** Take fraction shifted by 10 bits to left, round it, normalize it and detect exceptions

 * @param cexp exponent with bias

 * @param cfrac fraction shifted 10 places left with added hidden bit

 * @param sign

 * @return valied float64

 */

float64 finishFloat64(int32_t cexp, uint64_t cfrac, char sign)

{

	float64 result;

	result.parts.sign = sign;

	/* find first nonzero digit and shift result and detect possibly underflow */

	while ((cexp > 0) && (cfrac) && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ) )))) {

		cexp--; 

		cfrac <<= 1;

			/* TODO: fix underflow */

	};

	if ((cexp < 0) || ( cexp == 0 && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1)))))) {

		/* FIXME: underflow */

		result.parts.exp = 0;

		if ((cexp + FLOAT64_FRACTION_SIZE + 1) < 0) { /* +1 is place for rounding */

			result.parts.fraction = 0;

			return result;

		}

		while (cexp < 0) {

			cexp++;

			cfrac >>= 1;

		}

		cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3)); 

		if (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1)))) {

			result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2) ) & (~FLOAT64_HIDDEN_BIT_MASK)); 

			return result;

		}	

	} else {

		cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3)); 

	}

	++cexp;

	if (cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ))) {

		++cexp;

		cfrac >>= 1;

	}	

	/* check overflow */

	if (cexp >= FLOAT64_MAX_EXPONENT ) {

		/* FIXME: overflow, return infinity */

		result.parts.exp = FLOAT64_MAX_EXPONENT;

		result.parts.fraction = 0;

		return result;

	}

	result.parts.exp = (uint32_t)cexp;

	result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2 ) ) & (~FLOAT64_HIDDEN_BIT_MASK)); 

	return result;	

}

/** Counts leading zeroes in 64bit unsigned integer

 * @param i 

 */

int countZeroes64(uint64_t i)

{

	int j;

	for (j =0; j < 64; j += 8) {

		if ( i & (0xFFll << (56 - j))) {

			return (j + countZeroes8(i >> (56 - j)));

		}

	}

	return 64;

}

/** Counts leading zeroes in 32bit unsigned integer

 * @param i 

 */

int countZeroes32(uint32_t i)

{

	int j;

	for (j =0; j < 32; j += 8) {

		if ( i & (0xFF << (24 - j))) {

			return (j + countZeroes8(i >> (24 - j)));

		}

	}

	return 32;

}

/** Counts leading zeroes in byte

 * @param i 

 */

int countZeroes8(uint8_t i)

{

	return zeroTable[i];

}

/** Round and normalize number expressed by exponent and fraction with first bit (equal to hidden bit) at 30. bit

 * @param exp exponent 

 * @param fraction part with hidden bit shifted to 30. bit

 */

void roundFloat32(int32_t *exp, uint32_t *fraction)

{

	/* rounding - if first bit after fraction is set then round up */

	(*fraction) += (0x1 << 6);

	if ((*fraction) & (FLOAT32_HIDDEN_BIT_MASK << 8)) { 

		/* rounding overflow */

		++(*exp);

		(*fraction) >>= 1;

	};

	if (((*exp) >= FLOAT32_MAX_EXPONENT ) || ((*exp) < 0)) {

		/* overflow - set infinity as result */

		(*exp) = FLOAT32_MAX_EXPONENT;

		(*fraction) = 0;

		return;

	}

	return;

}

/** Round and normalize number expressed by exponent and fraction with first bit (equal to hidden bit) at 62. bit

 * @param exp exponent 

 * @param fraction part with hidden bit shifted to 62. bit

 */

void roundFloat64(int32_t *exp, uint64_t *fraction)

{

	/* rounding - if first bit after fraction is set then round up */

	(*fraction) += (0x1 << 9);

	if ((*fraction) & (FLOAT64_HIDDEN_BIT_MASK << 11)) { 

		/* rounding overflow */

		++(*exp);

		(*fraction) >>= 1;

	};

	if (((*exp) >= FLOAT64_MAX_EXPONENT ) || ((*exp) < 0)) {

		/* overflow - set infinity as result */

		(*exp) = FLOAT64_MAX_EXPONENT;

		(*fraction) = 0;

		return;

	}

	return;

}