/*
 *  reg_compare.c
 *
 * Compare two floating point registers
 *
 *
 * Copyright (C) 1992, 1993  W. Metzenthen, 22 Parker St, Ormond,
 *                           Vic 3163, Australia.
 *                           E-mail apm233m@vaxc.cc.monash.edu.au
 * All rights reserved.
 *
 * This copyright notice covers the redistribution and use of the
 * FPU emulator developed by W. Metzenthen. It covers only its use
 * in the 386BSD operating system. Any other use is not permitted
 * under this copyright.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must include information specifying
 *    that source code for the emulator is freely available and include
 *    either:
 *      a) an offer to provide the source code for a nominal distribution
 *         fee, or
 *      b) list at least two alternative methods whereby the source
 *         can be obtained, e.g. a publically accessible bulletin board
 *         and an anonymous ftp site from which the software can be
 *         downloaded.
 * 3. All advertising materials specifically mentioning features or use of
 *    this emulator must acknowledge that it was developed by W. Metzenthen.
 * 4. The name of W. Metzenthen may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED ``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
 * W. METZENTHEN 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.
 *
 *
 *     $Id:$
 * 
 */

/*---------------------------------------------------------------------------+
 | compare() is the core FPU_REG comparison function                         |
 +---------------------------------------------------------------------------*/
#include "param.h"
#include "proc.h"
#include "systm.h"
#include "machine/cpu.h"
#include "machine/pcb.h"

#include "fpu_emu.h"
#include "fpu_system.h"
#include "exception.h"
#include "control_w.h"
#include "status_w.h"


int
compare(FPU_REG * b)
{
	int     diff;

	if (FPU_st0_ptr->tag | b->tag) {
		if (FPU_st0_ptr->tag == TW_Zero) {
			if (b->tag == TW_Zero)
				return COMP_A_eq_B;
			if (b->tag == TW_Valid) {
#ifdef DENORM_OPERAND
				if ((b->exp <= EXP_UNDER) && (denormal_operand()))
					return COMP_Denormal;
#endif				/* DENORM_OPERAND */
				return (b->sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B;
			}
		} else
			if (b->tag == TW_Zero) {
				if (FPU_st0_ptr->tag == TW_Valid) {
#ifdef DENORM_OPERAND
					if ((FPU_st0_ptr->exp <= EXP_UNDER) && (denormal_operand()))
						return COMP_Denormal;
#endif				/* DENORM_OPERAND */
					return (FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B;
				}
			}
		if (FPU_st0_ptr->tag == TW_Infinity) {
			if ((b->tag == TW_Valid) || (b->tag == TW_Zero)) {
#ifdef DENORM_OPERAND
				if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER)
				    && (denormal_operand()))
					return COMP_Denormal;
#endif				/* DENORM_OPERAND */
				return (FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B;
			} else
				if (b->tag == TW_Infinity) {
					/* The 80486 book says that infinities
					 * can be equal! */
					return (FPU_st0_ptr->sign == b->sign) ? COMP_A_eq_B :
					    ((FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
				}
			/* Fall through to the NaN code */
		} else
			if (b->tag == TW_Infinity) {
				if ((FPU_st0_ptr->tag == TW_Valid) || (FPU_st0_ptr->tag == TW_Zero)) {
#ifdef DENORM_OPERAND
					if ((FPU_st0_ptr->tag == TW_Valid)
					    && (FPU_st0_ptr->exp <= EXP_UNDER)
					    && (denormal_operand()))
						return COMP_Denormal;
#endif				/* DENORM_OPERAND */
					return (b->sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B;
				}
				/* Fall through to the NaN code */
			}
		/* The only possibility now should be that one of the
		 * arguments is a NaN */
		if ((FPU_st0_ptr->tag == TW_NaN) || (b->tag == TW_NaN)) {
			if (((FPU_st0_ptr->tag == TW_NaN) && !(FPU_st0_ptr->sigh & 0x40000000))
			    || ((b->tag == TW_NaN) && !(b->sigh & 0x40000000)))
				/* At least one arg is a signaling NaN */
				return COMP_No_Comp | COMP_SNaN | COMP_NaN;
			else
				/* Neither is a signaling NaN */
				return COMP_No_Comp | COMP_NaN;
		}
		EXCEPTION(EX_Invalid);
	}
#ifdef PARANOID
	if (!(FPU_st0_ptr->sigh & 0x80000000))
		EXCEPTION(EX_Invalid);
	if (!(b->sigh & 0x80000000))
		EXCEPTION(EX_Invalid);
#endif				/* PARANOID */

#ifdef DENORM_OPERAND
	if (((FPU_st0_ptr->exp <= EXP_UNDER) ||
		(b->exp <= EXP_UNDER)) && (denormal_operand()))
		return COMP_Denormal;
#endif				/* DENORM_OPERAND */

	if (FPU_st0_ptr->sign != b->sign)
		return (FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B;

	diff = FPU_st0_ptr->exp - b->exp;
	if (diff == 0) {
		diff = FPU_st0_ptr->sigh - b->sigh;	/* Works only if ms bits
							 * are identical */
		if (diff == 0) {
			diff = FPU_st0_ptr->sigl > b->sigl;
			if (diff == 0)
				diff = -(FPU_st0_ptr->sigl < b->sigl);
		}
	}
	if (diff > 0)
		return (FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B;
	if (diff < 0)
		return (FPU_st0_ptr->sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B;
	return COMP_A_eq_B;

}


/* This function requires that st(0) is not empty */
int
compare_st_data(void)
{
	int     f, c;

	c = compare(&FPU_loaded_data);

	if (c & (COMP_NaN | COMP_Denormal)) {
		if (c & COMP_NaN) {
			EXCEPTION(EX_Invalid);
			f = SW_C3 | SW_C2 | SW_C0;
		} else {
			/* One of the operands is a de-normal */
			return 0;
		}
	} else
		switch (c) {
		case COMP_A_lt_B:
			f = SW_C0;
			break;
		case COMP_A_eq_B:
			f = SW_C3;
			break;
		case COMP_A_gt_B:
			f = 0;
			break;
		case COMP_No_Comp:
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#ifdef PARANOID
		default:
			EXCEPTION(EX_INTERNAL | 0x121);
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#endif				/* PARANOID */
		}
	setcc(f);
	return 1;
}


static int
compare_st_st(int nr)
{
	int     f, c;

	if (!NOT_EMPTY_0 || !NOT_EMPTY(nr)) {
		setcc(SW_C3 | SW_C2 | SW_C0);
		/* Stack fault */
		EXCEPTION(EX_StackUnder);
		return control_word & CW_Invalid;
	}
	c = compare(&st(nr));
	if (c & (COMP_NaN | COMP_Denormal)) {
		if (c & COMP_NaN) {
			setcc(SW_C3 | SW_C2 | SW_C0);
			EXCEPTION(EX_Invalid);
			return control_word & CW_Invalid;
		} else {
			/* One of the operands is a de-normal */
			return control_word & CW_Denormal;
		}
	} else
		switch (c) {
		case COMP_A_lt_B:
			f = SW_C0;
			break;
		case COMP_A_eq_B:
			f = SW_C3;
			break;
		case COMP_A_gt_B:
			f = 0;
			break;
		case COMP_No_Comp:
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#ifdef PARANOID
		default:
			EXCEPTION(EX_INTERNAL | 0x122);
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#endif				/* PARANOID */
		}
	setcc(f);
	return 1;
}


static int
compare_u_st_st(int nr)
{
	int     f, c;

	if (!NOT_EMPTY_0 || !NOT_EMPTY(nr)) {
		setcc(SW_C3 | SW_C2 | SW_C0);
		/* Stack fault */
		EXCEPTION(EX_StackUnder);
		return control_word & CW_Invalid;
	}
	c = compare(&st(nr));
	if (c & (COMP_NaN | COMP_Denormal)) {
		if (c & COMP_NaN) {
			setcc(SW_C3 | SW_C2 | SW_C0);
			if (c & COMP_SNaN) {	/* This is the only difference
						 * between un-ordered and
						 * ordinary comparisons */
				EXCEPTION(EX_Invalid);
				return control_word & CW_Invalid;
			}
			return 1;
		} else {
			/* One of the operands is a de-normal */
			return control_word & CW_Denormal;
		}
	} else
		switch (c) {
		case COMP_A_lt_B:
			f = SW_C0;
			break;
		case COMP_A_eq_B:
			f = SW_C3;
			break;
		case COMP_A_gt_B:
			f = 0;
			break;
		case COMP_No_Comp:
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#ifdef PARANOID
		default:
			EXCEPTION(EX_INTERNAL | 0x123);
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#endif				/* PARANOID */
		}
	setcc(f);
	return 1;
}
/*---------------------------------------------------------------------------*/

void
fcom_st()
{
	/* fcom st(i) */
	compare_st_st(FPU_rm);
}


void
fcompst()
{
	/* fcomp st(i) */
	if (compare_st_st(FPU_rm))
		pop();
}


void
fcompp()
{
	/* fcompp */
	if (FPU_rm != 1)
		return Un_impl();
	if (compare_st_st(1)) {
		pop();
		FPU_st0_ptr = &st(0);
		pop();
	}
}


void
fucom_()
{
	/* fucom st(i) */
	compare_u_st_st(FPU_rm);

}


void
fucomp()
{
	/* fucomp st(i) */
	if (compare_u_st_st(FPU_rm))
		pop();
}


void
fucompp()
{
	/* fucompp */
	if (FPU_rm == 1) {
		if (compare_u_st_st(1)) {
			pop();
			FPU_st0_ptr = &st(0);
			pop();
		}
	} else
		Un_impl();
}