tv.c

/*
 * Copyright (C) 1995-2007 University of Karlsruhe.  All right reserved.
 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

/**
 * @file
 * @brief    Representation of and static computations on target machine
 *           values.
 * @date     2003
 * @author   Mathias Heil
 * @version  $Id$
 * @summary
 *
 * Values are stored in a format depending upon chosen arithmetic
 * module. Default uses strcalc and fltcalc.
 * This implementation assumes:
 *  - target has IEEE-754 floating-point arithmetic.
 */
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>         /* assertions */
#include <stdlib.h>         /* atoi() */
#ifdef HAVE_STRING_H
# include <string.h>         /* nice things for strings */
#endif
#ifdef HAVE_STRINGS_H
#include <strings.h>        /* strings.h also includes bsd only function strcasecmp */
#endif
#ifdef HAVE_STDLIB_H
# include <stdlib.h>
#endif

#include "tv_t.h"
#include "set.h"            /* to store tarvals in */
#include "entity_t.h"       /* needed to store pointers to entities */
#include "irmode_t.h"
#include "irnode.h"         /* defines boolean return values (pnc_number)*/
#include "strcalc.h"
#include "fltcalc.h"
#include "irtools.h"
#include "xmalloc.h"
#include "firm_common.h"
#include "error.h"

/** Size of hash tables.  Should correspond to average number of distinct constant
    target values */
#define N_CONSTANTS 2048

/* get the integer overflow mode */
#define GET_OVERFLOW_MODE() int_overflow_mode

/* unused, float to int doesn't work yet */
enum float_to_int_mode {
	TRUNCATE,
	ROUND
};

#define GET_FLOAT_TO_INT_MODE() TRUNCATE

#define SWITCH_NOINFINITY 0
#define SWITCH_NODENORMALS 0

/****************************************************************************
 *   local definitions and macros
 ****************************************************************************/
#ifndef NDEBUG
#  define TARVAL_VERIFY(a) tarval_verify((a))
#else
#  define TARVAL_VERIFY(a) ((void)0)
#endif

#define INSERT_TARVAL(tv) ((tarval*)set_insert(tarvals, (tv), sizeof(tarval), hash_tv((tv))))
#define FIND_TARVAL(tv) ((tarval*)set_find(tarvals, (tv), sizeof(tarval), hash_tv((tv))))

#define INSERT_VALUE(val, size) (set_insert(values, (val), size, hash_val((val), size)))
#define FIND_VALUE(val, size) (set_find(values, (val), size, hash_val((val), size)))

#define fail_verify(a) _fail_verify((a), __FILE__, __LINE__)

/****************************************************************************
 *   private variables
 ****************************************************************************/
static struct set *tarvals = NULL;   /* container for tarval structs */
static struct set *values = NULL;    /* container for values */
static tarval_int_overflow_mode_t int_overflow_mode = TV_OVERFLOW_WRAP;

/** if this is set non-zero, the constant folding for floating point is OFF */
static int no_float = 0;

/****************************************************************************
 *   private functions
 ****************************************************************************/
#ifndef NDEBUG
static int hash_val(const void *value, unsigned int length);
static int hash_tv(tarval *tv);
static void _fail_verify(tarval *tv, const char* file, int line)
{
	/* print a memory image of the tarval and throw an assertion */
	if (tv)
		printf("%s:%d: Invalid tarval:\n  mode: %s\n value: [%p]\n", file, line, get_mode_name(tv->mode), tv->value);
	else
		printf("%s:%d: Invalid tarval (null)", file, line);
	assert(0);
}
#ifdef __GNUC__
INLINE static void tarval_verify(tarval *tv) __attribute__ ((unused));
#endif

INLINE static void tarval_verify(tarval *tv)
{
	assert(tv);
	assert(tv->mode);
	assert(tv->value);

	if ((tv == tarval_bad) || (tv == tarval_undefined)) return;
	if ((tv == tarval_b_true) || (tv == tarval_b_false)) return;

	if (!FIND_TARVAL(tv)) fail_verify(tv);
	if (tv->length > 0 && !FIND_VALUE(tv->value, tv->length)) fail_verify(tv);

	return;
}
#endif /* NDEBUG */

/** Hash a tarval. */
static int hash_tv(tarval *tv) {
	return (PTR_TO_INT(tv->value) ^ PTR_TO_INT(tv->mode)) + tv->length;
}

/** Hash a value. Treat it as a byte array. */
static int hash_val(const void *value, unsigned int length) {
	unsigned int i;
	unsigned int hash = 0;

	/* scramble the byte - array */
	for (i = 0; i < length; ++i) {
		hash += (hash << 5) ^ (hash >> 27) ^ ((char*)value)[i];
		hash += (hash << 11) ^ (hash >> 17);
	}

	return hash;
}

/** finds tarval with value/mode or creates new tarval */
static tarval *get_tarval(const void *value, int length, ir_mode *mode) {
	tarval tv;

	tv.kind   = k_tarval;
	tv.mode   = mode;
	tv.length = length;
	if (length > 0) {
		/* if there already is such a value, it is returned, else value
		 * is copied into the set */
		char *temp = alloca(sc_get_buffer_length());
		memcpy(temp, value, sc_get_buffer_length());
		sign_extend(temp, mode);
		tv.value = INSERT_VALUE(temp, length);
	} else {
		tv.value = value;
	}
	/* if there is such a tarval, it is returned, else tv is copied
	 * into the set */
	return (tarval *)INSERT_TARVAL(&tv);
}

/**
 * handle overflow
 */
static tarval *get_tarval_overflow(const void *value, int length, ir_mode *mode)
{
	char *temp;

	switch (get_mode_sort(mode)) {
	case irms_reference:
		/* addresses always wrap around */
		temp = alloca(sc_get_buffer_length());
		sc_val_from_ulong(-1, temp);
		sc_and(temp, value, temp);
		/* the sc_ module expects that all bits are set ... */
		sign_extend(temp, mode);
		return get_tarval(temp, length, mode);

	case irms_int_number:
		if (sc_comp(value, get_mode_max(mode)->value) == 1) {
			switch (GET_OVERFLOW_MODE()) {
			case TV_OVERFLOW_SATURATE:
				return get_mode_max(mode);
			case TV_OVERFLOW_WRAP:
				temp = alloca(sc_get_buffer_length());
				sc_val_from_ulong(-1, temp);
				sc_and(temp, value, temp);
				/* the sc_ module expects that all bits are set ... */
				sign_extend(temp, mode);
				return get_tarval(temp, length, mode);
			case TV_OVERFLOW_BAD:
				return tarval_bad;
			default:
				return get_tarval(value, length, mode);
			}
		}
		if (sc_comp(value, get_mode_min(mode)->value) == -1) {
			switch (GET_OVERFLOW_MODE()) {
			case TV_OVERFLOW_SATURATE:
				return get_mode_min(mode);
			case TV_OVERFLOW_WRAP: {
				char *temp = alloca(sc_get_buffer_length());
				sc_val_from_ulong(-1, temp);
				sc_and(temp, value, temp);
				return get_tarval(temp, length, mode);
			}
			case TV_OVERFLOW_BAD:
				return tarval_bad;
			default:
				return get_tarval(value, length, mode);
			}
		}
		break;

	case irms_float_number:
		if (SWITCH_NOINFINITY && fc_is_inf(value)) {
			return fc_is_negative(value)?get_mode_min(mode):get_mode_max(mode);
		}

		if (SWITCH_NODENORMALS && fc_is_subnormal(value)) {
			return get_mode_null(mode);
		}
		break;

	default:
		break;
	}
	return get_tarval(value, length, mode);
}

/*
 *   public variables declared in tv.h
 */
static tarval reserved_tv[4];

tarval *tarval_bad       = &reserved_tv[0];
tarval *tarval_undefined = &reserved_tv[1];
tarval *tarval_b_false   = &reserved_tv[2];
tarval *tarval_b_true    = &reserved_tv[3];

/*
 *   public functions declared in tv.h
 */

/*
 * Constructors =============================================================
 */
tarval *new_tarval_from_str(const char *str, size_t len, ir_mode *mode)
{
	assert(str);
	assert(len);
	assert(mode);

	switch (get_mode_sort(mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
		assert(0);
		break;

	case irms_internal_boolean:
		/* match [tT][rR][uU][eE]|[fF][aA][lL][sS][eE] */
		if (strcasecmp(str, "true")) return tarval_b_true;
		else if (strcasecmp(str, "false")) return tarval_b_true;
		else
			/* XXX This is C semantics */
			return atoi(str) ? tarval_b_true : tarval_b_false;

	case irms_float_number:
		switch (get_mode_size_bits(mode)) {
		case 32:
			fc_val_from_str(str, len, 8, 23, NULL);
			break;
		case 64:
			fc_val_from_str(str, len, 11, 52, NULL);
			break;
		case 80:
			fc_val_from_str(str, len, 15, 64, NULL);
			break;
		}
		return get_tarval(fc_get_buffer(), fc_get_buffer_length(), mode);

	case irms_reference:
		/* same as integer modes */
	case irms_int_number:
		sc_val_from_str(str, len, NULL, mode);
		return get_tarval(sc_get_buffer(), sc_get_buffer_length(), mode);
	}

	assert(0);  /* can't be reached, can it? */
	return NULL;
}

/*
 * helper function, create a tarval from long
 */
tarval *new_tarval_from_long(long l, ir_mode *mode) {
	assert(mode);

	switch (get_mode_sort(mode))   {
	case irms_internal_boolean:
		/* XXX C semantics ! */
		return l ? tarval_b_true : tarval_b_false ;

	case irms_reference:
		/* same as integer modes */
	case irms_int_number:
		sc_val_from_long(l, NULL);
		return get_tarval(sc_get_buffer(), sc_get_buffer_length(), mode);

	case irms_float_number:
		return new_tarval_from_double((long double)l, mode);

	default:
		assert(0 && "unsupported mode sort");
	}
	return NULL;
}

/* returns non-zero if can be converted to long */
int tarval_is_long(tarval *tv) {
	if (!mode_is_int(tv->mode) && !mode_is_reference(tv->mode))
		return 0;

	if (get_mode_size_bits(tv->mode) > (int) (sizeof(long) << 3)) {
		/* the value might be too big to fit in a long */
		sc_max_from_bits(sizeof(long) << 3, 0, NULL);
		if (sc_comp(sc_get_buffer(), tv->value) == -1) {
			/* really doesn't fit */
			return 0;
		}
	}
	return 1;
}

/* this might overflow the machine's long, so use only with small values */
long get_tarval_long(tarval* tv) {
	assert(tarval_is_long(tv) && "tarval too big to fit in long");

	return sc_val_to_long(tv->value);
}

tarval *new_tarval_from_double(long double d, ir_mode *mode) {
	assert(mode && (get_mode_sort(mode) == irms_float_number));

	switch (get_mode_size_bits(mode)) {
	case 32:
		fc_val_from_ieee754(d, 8, 23, NULL);
		break;
	case 64:
		fc_val_from_ieee754(d, 11, 52, NULL);
		break;
	case 80:
		fc_val_from_ieee754(d, 15, 64, NULL);
		break;
	}
	return get_tarval(fc_get_buffer(), fc_get_buffer_length(), mode);
}

/* returns non-zero if can be converted to double */
int tarval_is_double(tarval *tv) {
	assert(tv);

	return (get_mode_sort(tv->mode) == irms_float_number);
}

long double get_tarval_double(tarval *tv) {
	assert(tarval_is_double(tv));

	return fc_val_to_ieee754(tv->value);
}


/*
 * Access routines for tarval fields ========================================
 */

/* get the mode of the tarval */
ir_mode *(get_tarval_mode)(const tarval *tv) {
	return _get_tarval_mode(tv);
}

/*
 * Special value query functions ============================================
 *
 * These functions calculate and return a tarval representing the requested
 * value.
 * The functions get_mode_{Max,Min,...} return tarvals retrieved from these
 * functions, but these are stored on initialization of the irmode module and
 * therefore the irmode functions should be preferred to the functions below.
 */

tarval *(get_tarval_bad)(void) {
	return _get_tarval_bad();
}

tarval *(get_tarval_undefined)(void) {
	return _get_tarval_undefined();
}

tarval *(get_tarval_b_false)(void) {
	return _get_tarval_b_false();
}

tarval *(get_tarval_b_true)(void) {
	return _get_tarval_b_true();
}

tarval *get_tarval_max(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	switch(get_mode_sort(mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
		assert(0);
		break;

	case irms_internal_boolean:
		return tarval_b_true;

	case irms_float_number:
		switch(get_mode_size_bits(mode)) {
		case 32:
			fc_get_max(8, 23, NULL);
			break;
		case 64:
			fc_get_max(11, 52, NULL);
			break;
		case 80:
			fc_get_max(15, 64, NULL);
			break;
		}
		return get_tarval(fc_get_buffer(), fc_get_buffer_length(), mode);

	case irms_reference:
	case irms_int_number:
		sc_max_from_bits(get_mode_size_bits(mode), mode_is_signed(mode), NULL);
		return get_tarval(sc_get_buffer(), sc_get_buffer_length(), mode);
	}
	return tarval_bad;
}

tarval *get_tarval_min(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	switch(get_mode_sort(mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
		assert(0);
		break;

	case irms_internal_boolean:
		return tarval_b_false;

	case irms_float_number:
		switch(get_mode_size_bits(mode)) {
		case 32:
			fc_get_min(8, 23, NULL);
			break;
		case 64:
			fc_get_min(11, 52, NULL);
			break;
		case 80:
			fc_get_min(15, 64, NULL);
			break;
		}
		return get_tarval(fc_get_buffer(), fc_get_buffer_length(), mode);

	case irms_reference:
	case irms_int_number:
		sc_min_from_bits(get_mode_size_bits(mode), mode_is_signed(mode), NULL);
		return get_tarval(sc_get_buffer(), sc_get_buffer_length(), mode);
	}
	return tarval_bad;
}

/** The bit pattern for the pointer NULL */
static long _null_value = 0;

tarval *get_tarval_null(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	switch(get_mode_sort(mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
	case irms_internal_boolean:
		assert(0);
		break;

	case irms_float_number:
		return new_tarval_from_double(0.0, mode);

	case irms_int_number:
		return new_tarval_from_long(0l,  mode);

	case irms_reference:
		return new_tarval_from_long(_null_value, mode);
	}
	return tarval_bad;
}

tarval *get_tarval_one(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		assert(0);
		return tarval_bad;
	}

	switch(get_mode_sort(mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
		assert(0);
		break;

	case irms_internal_boolean:
		return tarval_b_true;

	case irms_float_number:
		return new_tarval_from_double(1.0, mode);

	case irms_reference:
	case irms_int_number:
		return new_tarval_from_long(1l, mode);
	}
	return tarval_bad;
}

tarval *get_tarval_all_one(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		assert(0);
		return tarval_bad;
	}

	switch(get_mode_sort(mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
		assert(0);
		return tarval_bad;

	case irms_int_number:
	case irms_internal_boolean:
	case irms_reference:
		return tarval_not(get_mode_null(mode));


	case irms_float_number:
		return new_tarval_from_double(1.0, mode);
	}
	return tarval_bad;
}

tarval *get_tarval_minus_one(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	switch(get_mode_sort(mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
	case irms_internal_boolean:
		assert(0);
		break;

	case irms_reference:
		return tarval_bad;

	case irms_float_number:
		return mode_is_signed(mode) ? new_tarval_from_double(-1.0, mode) : tarval_bad;

	case irms_int_number:
		return new_tarval_from_long(-1l, mode);
	}
	return tarval_bad;
}

tarval *get_tarval_nan(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	if (get_mode_sort(mode) == irms_float_number) {
		switch(get_mode_size_bits(mode)) {
		case 32:
			fc_get_qnan(8, 23, NULL);
			break;
		case 64:
			fc_get_qnan(11, 52, NULL);
			break;
		case 80:
			fc_get_qnan(15, 64, NULL);
			break;
		}
		return get_tarval(fc_get_buffer(), fc_get_buffer_length(), mode);
	} else {
		assert(0 && "tarval is not floating point");
		return tarval_bad;
	}
}

tarval *get_tarval_plus_inf(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	if (get_mode_sort(mode) == irms_float_number) {
		switch(get_mode_size_bits(mode)) {
		case 32:
			fc_get_plusinf(8, 23, NULL);
			break;
		case 64:
			fc_get_plusinf(11, 52, NULL);
			break;
		case 80:
			fc_get_plusinf(15, 64, NULL);
			break;
		}
		return get_tarval(fc_get_buffer(), fc_get_buffer_length(), mode);
	} else {
		assert(0 && "tarval is not floating point");
		return tarval_bad;
	}
}

tarval *get_tarval_minus_inf(ir_mode *mode) {
	assert(mode);

	if (get_mode_n_vector_elems(mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	if (get_mode_sort(mode) == irms_float_number) {
		switch(get_mode_size_bits(mode)) {
		case 32:
			fc_get_minusinf(8, 23, NULL);
			break;
		case 64:
			fc_get_minusinf(11, 52, NULL);
			break;
		case 80:
			fc_get_minusinf(15, 64, NULL);
			break;
		}
		return get_tarval(fc_get_buffer(), fc_get_buffer_length(), mode);
	} else {
		assert(0 && "tarval is not floating point");
		return tarval_bad;
	}
}

/*
 * Arithmethic operations on tarvals ========================================
 */

/*
 * test if negative number, 1 means 'yes'
 */
int tarval_is_negative(tarval *a) {
	assert(a);

	if (get_mode_n_vector_elems(a->mode) > 1) {
		/* vector arithmetic not implemented yet */
		assert(0 && "tarval_is_negative is not allowed for vector modes");
		return 0;
	}

	switch (get_mode_sort(a->mode)) {
	case irms_int_number:
		if (!mode_is_signed(a->mode)) return 0;
		else
			return sc_comp(a->value, get_mode_null(a->mode)->value) == -1 ? 1 : 0;

	case irms_float_number:
		return fc_comp(a->value, get_mode_null(a->mode)->value) == -1 ? 1 : 0;

	default:
		assert(0 && "not implemented");
		return 0;
	}
}

/*
 * test if null, 1 means 'yes'
 */
int tarval_is_null(tarval *a) {
	ir_mode *m = get_tarval_mode(a);

	return a == get_tarval_null(m);
}

/*
 * test if one, 1 means 'yes'
 */
int tarval_is_one(tarval *a) {
	ir_mode *m = get_tarval_mode(a);

	return a == get_tarval_one(m);
}

/*
 * comparison
 */
pn_Cmp tarval_cmp(tarval *a, tarval *b) {
	assert(a);
	assert(b);

	if (a == tarval_bad || b == tarval_bad) {
		assert(0 && "Comparison with tarval_bad");
		return pn_Cmp_False;
	}

	if (a == tarval_undefined || b == tarval_undefined)
		return pn_Cmp_False;

	if (a->mode != b->mode)
		return pn_Cmp_False;

	if (get_mode_n_vector_elems(a->mode) > 1) {
		/* vector arithmetic not implemented yet */
		assert(0 && "cmp not implemented for vector modes");
	}

	/* Here the two tarvals are unequal and of the same mode */
	switch (get_mode_sort(a->mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
		if (a == b)
			return pn_Cmp_Eq;
		return pn_Cmp_False;

	case irms_float_number:
		if (no_float)
			return pn_Cmp_False;
		/*
		 * BEWARE: we cannot compare a == b here, because
		 * a NaN is always Unordered to any other value, even to itself!
		 */
		switch (fc_comp(a->value, b->value)) {
		case -1: return pn_Cmp_Lt;
		case  0: return pn_Cmp_Eq;
		case  1: return pn_Cmp_Gt;
		case  2: return pn_Cmp_Uo;
		default: return pn_Cmp_False;
		}
	case irms_reference:
	case irms_int_number:
		if (a == b)
			return pn_Cmp_Eq;
		return sc_comp(a->value, b->value) == 1 ? pn_Cmp_Gt : pn_Cmp_Lt;

	case irms_internal_boolean:
		if (a == b)
			return pn_Cmp_Eq;
		return a == tarval_b_true ? pn_Cmp_Gt : pn_Cmp_Lt;
	}
	return pn_Cmp_False;
}

/*
 * convert to other mode
 */
tarval *tarval_convert_to(tarval *src, ir_mode *dst_mode) {
	char *buffer;
	fp_value *res;

	assert(src);
	assert(dst_mode);

	if (src->mode == dst_mode) return src;

	if (get_mode_n_vector_elems(src->mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	switch (get_mode_sort(src->mode)) {
	case irms_control_flow:
	case irms_memory:
	case irms_auxiliary:
		break;

		/* cast float to something */
	case irms_float_number:
		switch (get_mode_sort(dst_mode)) {
		case irms_float_number:
			switch (get_mode_size_bits(dst_mode)) {
			case 32:
				fc_cast(src->value, 8, 23, NULL);
				break;
			case 64:
				fc_cast(src->value, 11, 52, NULL);
				break;
			case 80:
				fc_cast(src->value, 15, 64, NULL);
				break;
			default:
				break;
			}
			return get_tarval(fc_get_buffer(), fc_get_buffer_length(), dst_mode);

		case irms_int_number:
			switch (GET_FLOAT_TO_INT_MODE()) {
			case TRUNCATE:
				res = fc_int(src->value, NULL);
				break;
			case ROUND:
				res = fc_rnd(src->value, NULL);
				break;
			default:
				assert(0);
				break;
			}
			if (! fc_flt2int(res, sc_get_buffer(), dst_mode))
				return tarval_bad;
			return get_tarval(sc_get_buffer(), sc_get_buffer_length(), dst_mode);

		default:
			/* the rest can't be converted */
			return tarval_bad;
		}
		break;

	/* cast int/characters to something */
	case irms_int_number:
		switch (get_mode_sort(dst_mode)) {

		case irms_reference:
		case irms_int_number:
			buffer = alloca(sc_get_buffer_length());
			memcpy(buffer, src->value, sc_get_buffer_length());
			sign_extend(buffer, dst_mode);
			return get_tarval_overflow(buffer, src->length, dst_mode);

		case irms_internal_boolean:
			/* XXX C semantics */
			if (src == get_mode_null(src->mode)) return tarval_b_false;
			else return tarval_b_true;

		case irms_float_number:
			/* XXX floating point unit does not understand internal integer
			 * representation, convert to string first, then create float from
			 * string */
			buffer = alloca(100);
			/* decimal string representation because hexadecimal output is
			 * interpreted unsigned by fc_val_from_str, so this is a HACK */
			snprintf(buffer, 100, "%s",
				sc_print(src->value, get_mode_size_bits(src->mode), SC_DEC, mode_is_signed(src->mode)));
			buffer[100 - 1] = '\0';
			switch (get_mode_size_bits(dst_mode)) {
			case 32:
				fc_val_from_str(buffer, 0, 8, 23, NULL);
				break;
			case 64:
				fc_val_from_str(buffer, 0, 11, 52, NULL);
				break;
			case 80:
				fc_val_from_str(buffer, 0, 15, 64, NULL);
				break;
			}
			return get_tarval(fc_get_buffer(), fc_get_buffer_length(), dst_mode);

		default:
			break;
		}
		break;

	case irms_internal_boolean:
		/* beware: this is C semantic for the INTERNAL boolean mode */
		if (get_mode_sort(dst_mode) == irms_int_number)
			return src == tarval_b_true ? get_mode_one(dst_mode) : get_mode_null(dst_mode);
		break;

	case irms_reference:
		if (get_mode_sort(dst_mode) == irms_int_number) {
			buffer = alloca(sc_get_buffer_length());
			memcpy(buffer, src->value, sc_get_buffer_length());
			sign_extend(buffer, src->mode);
			return get_tarval_overflow(buffer, src->length, dst_mode);
		}
		break;
	}

	return tarval_bad;
}

/*
 * bitwise negation
 */
tarval *tarval_not(tarval *a) {
	char *buffer;

	assert(a);

	/* works for vector mode without changes */

	switch (get_mode_sort(a->mode)) {
	case irms_reference:
	case irms_int_number:
		buffer = alloca(sc_get_buffer_length());
		sc_not(a->value, buffer);
		return get_tarval(buffer, a->length, a->mode);

	case irms_internal_boolean:
		if (a == tarval_b_true)
			return tarval_b_false;
		if (a == tarval_b_false)
			return tarval_b_true;
		return tarval_bad;

	default:
		assert(0 && "bitwise negation is only allowed for integer and boolean");
		return tarval_bad;
	}
}

/*
 * arithmetic negation
 */
tarval *tarval_neg(tarval *a) {
	char *buffer;

	assert(a);
	assert(mode_is_num(a->mode)); /* negation only for numerical values */

	/* note: negation is allowed even for unsigned modes. */

	if (get_mode_n_vector_elems(a->mode) > 1) {
		/* vector arithmetic not implemented yet */
		return tarval_bad;
	}

	switch (get_mode_sort(a->mode)) {
	case irms_int_number:
		buffer = alloca(sc_get_buffer_length());
		sc_neg(a->value, buffer);
		return get_tarval_overflow(buffer, a->length, a->mode);

	case irms_float_number:
		if(no_float)
			return tarval_bad;

		fc_neg(a->value, NULL);
		return get_tarval_overflow(fc_get_buffer(), fc_get_buffer_length(), a->mode);