path: root/private/sdktools/masm/asmeval.c

/* asmeval.c -- microsoft 80x86 assembler
**
** microsoft (r) macro assembler
** copyright (c) microsoft corp 1986.  all rights reserved
**
** randy nevin
**
** 10/90 - Quick conversion to 32 bit by Jeff Spencer
*/

#include <stdio.h>
#include "asm86.h"
#include "asmfcn.h"
#include "asmexpr.h"


char parseset[] = {14,
		   OPUNPLUS,  OPPLUS,
		   OPMINUS,   OPUNMINUS,
		   OPHIGH,    OPLOW,
		   OPDOT,     OPOFFSET,
		   OPCOLON,   OPLPAR,
		   OPLBRK,    OPTHIS,
		   OPSHORT,   OPPTR};

/* POPvalue pops a operand from the top of the evaluation stack
	   If the item is not an operand or the stack is empty, an
	   error is generated and a value of 0 is supplied. The operand
	   is returned to the caller in <valu> and is a result type
	   operand. The original operand will not be a result unless it
	   has been already used. The operand entry is destroyed and a
	   result operand is created for constants and symbols( which
	   are not record/struc names or fields ). */




/***	valerror - process error in operand entry
 *
 *	valerror (p);
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */



VOID PASCAL CODESIZE
valerror (
	register struct ar	*p
){
	DSCREC *oldlast;

	/* Operand was expected */
	errorc (E_OPN);
	/* save expr stack */
	oldlast = p->lastitem;
	p->lastitem = defaultdsc ();
	/*  Point to rest */
	p->lastitem->previtem = oldlast;
}




/***	popvalue - pop operand entry off parse stack
 *
 *	dscrec = popvalue (p);
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */



DSCREC * PASCAL CODESIZE
popvalue (
	register struct ar	*p
){
	register DSCREC *valu;

	if (!p->lastitem)
		valerror (p);
	if (p->lastitem->itype != OPERAND)
		valerror (p);
	/* If not operand, insert one at LASTitem */
	/* In case need to convert */
	valu = p->lastitem;
	/* Assume won't convert */
	/* Pop operand off stack */
	p->lastitem = valu->previtem;
	return (valu);
}




/***	popoperator - pop next operator from stack
 *
 *	op = popoperator (p);
 *
 *	Entry	*p = parse stack entry
 *	Exit
 *	Returns operator
 *	Calls
 */


UCHAR PASCAL CODESIZE
popoperator (
	register struct ar	*p
){
	register char op;

	if (!p->lastitem) {
		errorc( E_OPR );  /* expected operator */
		return( (char)OPPLUS );  /* use '+' as default */
	}
	else {
		if (p->lastitem->itype != OPERATOR) {
			errorc( E_OPR );  /* expected operator */
			return( (char)OPPLUS );  /* use '+' as default */
		}
		else {
			/* Return OPERATOR number */
			op = p->lastitem->dsckind.opr.oidx;
			/* Pop OPERATOR off stack */
			itemptr = p->lastitem;
			p->lastitem = p->lastitem->previtem;
			return (op);
		}
	}
}


/* Evaluate is called to evaluate part of the expression. It is
	   usually called just before a lower precedence is pushed, but
	   also when the expression is complete and for close parens of
	   various kinds regadless of precedence. The amount of the
	   expression stack evauated depends on the caller. There are
	   3 cases:

		1. Lower precedence OPERATOR( 3+4*5 AND 3 ). Evaluate
		   back until left paren or precedence<= OPERATOR. If
		   paren, leave on stack.

		2. A paren of some kind( )>] ). Evaluate back to match-
		   ing paren. Leave paren off stack. If any other paren
		   seen, cause error.

		3. End of expression( ENDexpr TRUE ). Evaluate all that
		   is left of expression.

 */

/***	pushpar - push paren or bracket back onto stack
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


VOID PASCAL CODESIZE
pushpar (
	register struct evalrec	*p
){
	itemptr->previtem = p->p->lastitem;
	p->p->lastitem = itemptr;
	/* So OPERATOR not removed */
	itemptr = NULL;
}
/* EVALtop evaluates the top OPERATOR on the stack and its
	   operands and produces CURresult as a result. It assumes that
	   the stack is arranged as follows:

		Operand( If not already result type, will convert )

		OPERATOR( <> will cause error, [ executes as OPERATOR
			  ( will not evaluate, but whether stays on
			  stack is determined by PARENflag )

		Operand ( If not result, will convert. If OPERATOR is
			  unary, will not be looked for. Special check
			  for +/- used as unary. )

	   Any deviation from the above will cause an error to be
	   generated by popvalue/popoperator. */


/***	signadjust - calculate offset and sign of result and put in right operand
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 *	Note	Right and left operands may be switched
 */


VOID PASCAL CODESIZE
signadjust (
	UCHAR	minus,
	register struct exprec *p
){
	register struct psop *psol;	/* parse stack operand structure */
	register struct psop *psor;	/* parse stack operand structure */
	DSCREC	       *t;
	OFFSET maxInt;
	char   fOverflow = FALSE;

	maxInt = (fArth32)? OFFSETMAX: 0xffff;

	psor = &(p->valright->dsckind.opnd);
	psol = &(p->valleft->dsckind.opnd);

	if (psol->s)		  /* arthmethic on data size item - NEAR/FAR */
	    errorc(E_TIL);

	if (minus)
		psor->dsign = !psor->dsign;

	if (psol->dsegment || psol->dflag == XTERNAL ||
	    (M_FLTSTACK & psol->dtype)) {
		/* Want to preserve Left operand */
		t = p->valleft;
		p->valleft = p->valright;
		p->valright = t;
		p->right = p->left;
		p->left = p->valleft->dsckind.opnd.doffset;
		psor = &(p->valright->dsckind.opnd);
		psol = &(p->valleft->dsckind.opnd);
	}
	if (psol->dflag == UNDEFINED)
		psor->dtype = M_CODE | M_FORTYPE;

	if (psor->dflag == UNDEFINED && !(psol->dtype & M_PTRSIZE))
		psol->dsize = 0;

	if (psol->dsign == psor->dsign) {
		/* Signs are same */
		fOverflow = (((maxInt - p->right) + 1) == p->left);
		p->right = p->right + p->left;
	} else if (p->right > p->left)
		/* Different signs */
		p->right = p->right - p->left;
	else {
		p->right = p->left - p->right;
		psor->dsign = !psor->dsign;
	}

	if (p->right == 0 && !fOverflow)
		psor->dsign = FALSE;
	if (psor->dsign && (psor->dtype & M_SEGRESULT))
		errorc (E_OSA);
	psor->doffset = p->right;
}




/***	foldsigns - force evaluating 17 bit signed values back to 16 bits
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


VOID PASCAL CODESIZE
foldsigns (
	register struct exprec	*p
){
	/* the forms inside the comments seem to be trying to manage
	 * things as unsigned short even though they are stored in a
	 * larger field--ie this would be running as a cross assembler
	 * from a 32 bit host to a 16 bit object.  since for the 386,
	 * we keep all this stuff as long, this turns out to be a bad
	 * approach.  so without completely understanding what is going
	 * on, I am doing a simple negate (on the OFFSET field, which
	 * is probably an unsigned long) rather than trying to preserve
	 * the odd typing of the previous version  -Hans, 19/9/86 */

	if (p->valright->dsckind.opnd.dsign)
		/* p->right = 65535 - p->right + 1; */
		p->right = -p->right;
	if (p->valleft)
		if (p->valleft->dsckind.opnd.dsign)
			/* p->left = 65535 - p->left + 1; */
			p->left = -p->left;
}




/***	shiftoper - execute shift left or right
 *
 *	result = shiftoper (p);
 *
 *	Entry	*p = parse stack entry
 *	Exit	none
 *	Returns shifted value
 *	Calls
 */


OFFSET PASCAL CODESIZE
shiftoper (
	register struct exprec	*p
){
	register OFFSET  argl;
	register USHORT  argr;

	argl = p->valleft->dsckind.opnd.doffset;
	if (p->valleft->dsckind.opnd.dsign)
		argl = -argl;
	argr = p->valright->dsckind.opnd.doffset;
	if (p->valright->dsckind.opnd.dsign) {
		errorc (E_SCN);
		return (argl);
	}
	else if (sizeof(OFFSET)*8 < argr)
		return (0);
	else if (p->stkoper == OPSHL)
		return (argl << argr);
	else
		return (argl >> argr);
}

/* VALcheck is used by all OPERATOR execute routines to make
	   sure their arguments are correct. If the arguments are
	   expected to be some kind of result( i.e. not a structure
	   or record item or data size ), the old argument is destroy-
	   ed and DEFAULTdsc is called to create a substitute. Error
	   messages are also generated on type mismatches. A number
	   of procedures of the form: VALUExxxx are called, these
	   check if the given argument is of that type and if not,
	   generate an error and a value of zero. There is one kludge
	   in this procedure, the LENGTH OPERATOR should work with
	   records and structures, but these are still in the form of
	   <Isym> records so they will work with MASK, ...
	   The operand types are as follows:

	Callabs 	May be unary or binary. In any case, all
			values must have a NIL segment.

	Clsize		May be unary or binary. If unary, value must
			be a size( which is: structure name, -2 .. n
			or BYTE WORD ... ). If binary, left value is
			a size.

	Csame		Is always binary. If not results, coerce them.
			Both must belong to the same segment and not
			be external.

	Cdata		Is always unary. Result must be associated
			with data( Dtype is [data] ). Exception if
			LENGTH OPERATOR and is record or record field
			in which case converts to approriate result
			record.

	Ccode		Is always unary. Result must be associated
			with code( Dtype is [code] ).

	Crec		Is always unary. Value must be record field
			or record name.

	Cseg		Is always unary. Value must have a segment.

	Cvar		Always unary. Value must be constant or data
			or code.

	Clseg		Always binary. The left value must be a
			SEGresult or a segment register.

	Coneabs 	Always binary. One of the values must be a
			constant.

	Csamabs 	Always binary. Either both values have the
			same segment or the second value is a constant

 */




/***	valconst - give error if value is not constant
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


VOID PASCAL CODESIZE
valconst (
	register DSCREC	*arg
){
	if (!(M_RCONST & arg->dsckind.opnd.dtype) ||
	      arg->dsckind.opnd.dsegment ||
	      arg->dsckind.opnd.dflag == XTERNAL)
		/* Not constant */
		errorc (E_CXP);
}


/***	valusize - check size of operand
 *
 *	val = valusize (arg);
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


USHORT PASCAL CODESIZE
valuesize (
	register DSCREC *arg
){
	if (!fArth32)
	   arg->dsckind.opnd.doffset = (long) (SHORT) arg->dsckind.opnd.doffset;

	if (arg->dsckind.opnd.doffset == 0) {
		/* 0 means no size */
		errorc (E_OHS);
		return (0);
	}
	else if (arg->dsckind.opnd.doffset >= CSFAR_LONG)
		return (xltsymtoresult[PROC]);
	else
		return (xltsymtoresult[DVAR]);
}




/***	valcheck - check operand value
 *
 *	valcheck (valtype, unary, p);
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


VOID PASCAL CODESIZE
valcheck (
	UCHAR	valtype,
	UCHAR	unary,
	register struct exprec	*p
){
	register struct psop *psol;	/* parse stack operand structure */
	register struct psop *psor;	/* parse stack operand structure */

	psol = &(p->valleft->dsckind.opnd);
	psor = &(p->valright->dsckind.opnd);
	/* Should give error if have 2 externals */
	if (p->valleft)
		if (psol->dflag == XTERNAL && psor->dflag == XTERNAL)
			errorc (E_IUE);
	switch (valtype) {
		case CALLABS:
			valconst (p->valright);
			if (!unary)
				valconst (p->valleft);
			break;
		case CLSIZE:
			if (unary)
				psor->dtype = valuesize (p->valright);
			else
				psol->dtype = valuesize (p->valleft);
			break;
		case CSAME:
			if (psol->dsegment != psor->dsegment)
				errorc (E_OMM);
			break;
		case CDATA:
			if ((p->stkoper != OPLENGTH) || !psor->dextptr
			    || (psor->dflag == XTERNAL)) {
				if (!(M_DATA & psor->dtype) &&
				    (psor->dlength == 0))
					errorc (E_ASD);
			}
			else {
				/* Special case for LENGTH */
				p->valleft = defaultdsc ();
				/* Create value */
				p->valleft->prec = p->valright->prec;
				psol = &(p->valleft->dsckind.opnd);
				psol->dlength = psor->dextptr->length;
				/* Lose old value */
				oblititem (p->valright);
				p->valright = p->valleft;
				p->valleft = NULL;
				psor = psol;
				psol = NULL;
			}
			break;
		case CCODE:
			if (!(M_CODE & p->valright->dsckind.opnd.dtype))
			    errorc (E_ASC);
			break;
		case CREC:
			if (!psor->dextptr || psor->dflag == XTERNAL)
				errorc (E_RRF);
			break;
		case CSEG:
			if (!psor->dsegment && psor->dflag != XTERNAL
			    || (M_REGRESULT & psor->dtype))
				errorc (E_OSG);
			break;
		case CLSEG:
			if (M_SEGRESULT & psol->dtype) {
				/* ??? if (!psor->dsegment || (psor->dtype & M_RCONST))
					errorc (E_IOT); ??? */
			}
			else if (M_REGRESULT & psol->dtype) {
				if (psol->dsegment->symu.regsym.regtype != SEGREG)
					errorc (E_LOS);
			}
			else
				errorc (E_LOS);
			break;
		case CONEABS:
			if (psor->dsegment && psol->dsegment)
				errorc (E_OOC);
			break;
		case CSAMABS:
			if (psor->dsegment &&
			    psol->dsegment != psor->dsegment)
				errorc (E_OSA);
			break;
	}
	p->right = psor->doffset;
	if (p->valleft)
		p->left = psol->doffset;
}




/***	regcheck - check for <arg> a register in [...]
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


DSCREC * PASCAL CODESIZE
regcheck (
	DSCREC	*arg,
	UCHAR	minus,
	register struct exprec	*ptr
){
	struct psop *pso;	   /* parse stack operand structure */
	register struct ar *pAR;
	USHORT	reg;

	pso = &(arg->dsckind.opnd);
	pAR = ptr->p->p;

	if (M_REGRESULT & pso->dtype) {

		/* Is some register */
		if (ptr->p->parenflag || pAR->bracklevel) {

			/* Have index reg in []s */
			/* Lose size based on register */

			pso->dsize = 0;
			reg = pso->dsegment->offset;

			/* Must be index or ptr reg */

			switch(pso->dsegment->symu.regsym.regtype)
			{
			default:
				errorc (E_IBR);
				break;
			case INDREG:
				if (reg <= 5)

				    /* Have base reg BX | BP */

				    if (pAR->base)
					    errorc (E_DBR);
				    else
					    pAR->base = reg;

				else /* Have index reg DI | SI */

				    if (pAR->index)
					    errorc (E_DIR);
				    else
					    pAR->index = reg;
				break;
#ifdef V386
			case DWRDREG:

				/* Have 386 reg in []s */

				if (minus == 2)
				{
				    if (pAR->index & 0xf)
					    errorc(E_DIR);

				    pAR->index |= 8 | reg;
				}
				else if (pAR->base)
				{
				    if (pAR->index)
					    errorc(E_DIR);

				    if (reg == 4) {

				       /* swap base with index
				       * to allow [index][eSp] */

					pAR->index = pAR->base;
					pAR->base = 4|8;
				    }
				    else
					pAR->index = reg|8;
				}
				else
				    pAR->base = reg|8;

				break;
#endif /* V386 */
			}
			if (minus == TRUE && (ptr->valright == arg))
				errorc (E_IUR);

			oblititem (arg);
			return (defaultdsc ());
		}
		else {
		    errorc(E_IUR);
		    return (arg);
		}
	}

#ifdef V386   /* scaled indexing modes */

	else if (minus == 2 && (M_RCONST & pso->dtype))
	{
		if (pAR->index&0x70)
			errorc(E_MBR);

		if (highWord(arg->dsckind.opnd.doffset))
			goto scaleErr;

		switch((SHORT) arg->dsckind.opnd.doffset) {

		case 1:
			pAR->index |= 0x10;
			break;
		case 2:
			pAR->index |= 0x20;
			break;
		case 4:
			pAR->index |= 0x30;
			break;
		case 8:
			pAR->index |= 0x40;
			break;

		scaleErr:
		default:
			error(E_EXP, "scale value of 1,2,4 or 8");
		}
		oblititem (arg);
		return (defaultdsc ());
	}
#endif /* V386 */

	else return (arg);
}




/***	idxcheck - check for arg to +- is register
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 *	Note	See if arg to +/- is register, in which case see if should
 *		be stored in Ridx or Rbas due to []s
 */


VOID PASCAL CODESIZE
idxcheck (
	UCHAR minus,
	register struct exprec	*p
){
	p->valleft = regcheck (p->valleft, minus, p);
	p->valright = regcheck (p->valright, minus, p);
	p->right = p->valright->dsckind.opnd.doffset;
	p->left = p->valleft->dsckind.opnd.doffset;
}



/***	makeGrpRel - make an offset group relative
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


VOID PASCAL CODESIZE
makeGrpRel (
	register struct psop *p
){
	if (!(p->dtype&M_EXPLCOLON) && p->dsegment &&
	    p->dsegment->symkind == SEGMENT && p->dsegment->symu.segmnt.grouptr){

	    p->dtype |= M_GROUPSEG;
	    p->dcontext = p->dsegment->symu.segmnt.grouptr;
	}
}



/***	evaltop - evaluate top entry
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


VOID PASCAL CODESIZE
evaltop (
	struct evalrec *ptr
){
	register struct psop *psol;	/* parse stack operand structure */
	register struct psop *psor;	/* parse stack operand structure */
	struct exprec	a;

	a.p = ptr;
	/* Get right operand */
	a.valright = popvalue (a.p->p);
	itemptr = NULL;
	if (a.p->p->lastitem) {

	    /* Get OPERATOR */
	    a.stkoper = popoperator (a.p->p);
	    a.valleft = NULL;
	    /* assume is unary */
	    if (!inset (a.stkoper, unaryset))
		    /* Not unary OPERATOR */
		    a.valleft = (a.stkoper == OPUNPLUS || a.stkoper == OPUNMINUS)
			    ? defaultdsc() : popvalue (a.p->p);
	    /* Save for EVALtop */
	    a.p->idx = a.stkoper;
	    if (a.valleft)
		    a.valleft->prec = a.valright->prec;
	    psol = &(a.valleft->dsckind.opnd);
	    psor = &(a.valright->dsckind.opnd);

	    switch (a.stkoper) {

	/* All OPERATORs are executed thru this CASE statement. The
	 * VALcheck routine makes sure operands are of the correct
	 * type and may create dummy entries in the case of the real
	 * operand not being of type result when required. The REStype
	 * routine uses it's argument to know what part of the result
	 * record should be kept and the type of the result. Unary
	 * and binary OPERATORs both return their results in VALright. */

	       case OPAND:
	       case OPOR:
	       case OPXOR:
		       /* Make sure operands ok */
		       valcheck (CALLABS, FALSE, &a);
		       /*  Must work on 16 bits */
		       foldsigns (&a);
		       switch (a.stkoper) {
			       case OPAND:
				       psor->doffset = a.left & a.right;
				       break;
			       case OPOR:
				       psor->doffset = a.left | a.right;
				       break;
			       case OPXOR:
				       psor->doffset = a.left ^ a.right;
				       break;
		       }
		       psor->dsign = FALSE;
		       /*  Must clear out Dsign in case was signed value */
		       break;
	       case OPNOT:
		       /* TRUE constant arg */
		       valcheck (CALLABS, TRUE, &a);
		       foldsigns (&a);
		       psor->doffset = ~a.right;
		       psor->dsign = FALSE;
		       if (optyp == TDB &&
			   (psor->doffset & ((OFFSET) ~0xff)) == ((OFFSET) ~0xff))
			       psor->doffset &= 0xFF;
#ifdef V386_noCode

		       if (!(cputype & P386))	       /* truncate result to 16 bits */
			  psor->doffset &= 0xffff;    /* for compatablity */
#endif
		       break;
	       case OPSHL:
	       case OPSHR:
		       valcheck (CALLABS, FALSE, &a);
		       psor->doffset = shiftoper (&a);
		       psor->dsign = FALSE;
		       break;
	       case OPSEG:
		       /* Must have segment */
		       valcheck (CSEG, TRUE, &a);

		       if (psor->dcontext && !(psor->dtype&M_EXPLCOLON))
			   psor->dsegment = psor->dcontext;

		       psor->dtype = (psor->dtype&M_FORTYPE) | M_SEGRESULT| M_RCONST;
		       psor->doffset = 0;
		       psor->dsign = FALSE;

		       break;
	       case OPDOT:
		       /* See if idx reg */
		       idxcheck (FALSE, &a);
		       valcheck (CONEABS, FALSE, &a);
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);
		       if (psor->dsize)
			       psol->dsize = psor->dsize;
		       /* Adjust signs on records */
		       signadjust (FALSE, &a);
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);
		       break;
	       case OPUNPLUS:
	       case OPPLUS:
		       /* See if idx reg */
		       idxcheck (FALSE, &a);
		       valcheck (CONEABS, FALSE, &a);
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);
		       /* Adjust signs on records */
		       signadjust (FALSE, &a);
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);
		       break;
	       case OPUNMINUS:
	       case OPMINUS:
		       idxcheck (TRUE, &a);
		       if (psor->dsegment == psol->dsegment &&
			   psol->dsegment) {
			       if (psol->dtype & M_SEGRESULT) {
				       psol->dtype = M_SEGRESULT | M_RCONST;
				       psol->doffset = 0;
				       psol->dsign = FALSE;
			       }
			       if (psor->dtype & M_SEGRESULT) {
				       psor->dtype = M_SEGRESULT | M_RCONST;
				       psor->doffset = 0;
				       psor->dsign = FALSE;
			       }
		       }
		       valcheck (CSAMABS, FALSE, &a);
		       signadjust (TRUE, &a);
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);
		       if (psol->dsegment) {
			       /* clear Dcontext if have var-var */
			       psor->dtype = (psor->dtype &
				   (M_EXPLOFFSET | M_PTRSIZE | M_FORTYPE)) | M_RCONST;
			       psor->dsegment = NULL;
			       psor->dcontext = NULL;
			       psor->dsize = 0;
			       oblititem (a.valleft);
			       a.valleft = NULL;
		       }
		       break;
	       case OPMULT:
#ifdef V386
		       if (M_REGRESULT & (psol->dtype|psor->dtype))
		       {
			   if (cputype&P386) {
			       idxcheck (2, &a);
			       if (a.p->p->index&0x78)
				   break;
			   } else
			       errorc (E_IRV);
		       }
#endif
		       /* fall through */
	       case OPDIV:
		       valcheck (CALLABS, FALSE, &a);
		       /* Both are constant */
		       if (a.stkoper == OPMULT)
			       psor->doffset = a.left * a.right;
		       else if (a.right == 0)
			       errorc (E_DVZ);
		       else
			       psor->doffset = a.left / a.right;
		       if (psor->doffset == 0)
			       psor->dsign = FALSE;
		       else
			       psor->dsign = (psol->dsign != psor->dsign);
		       break;
	       case OPHIGH:
		       if (psor->dtype & M_RCONST) {
			       if (psor->dsign) {
				       psor->doffset = -psor->doffset;
				       psor->dsign = 0;
				       }
			       psor->doffset = psor->doffset >> 8 & 0xff;
		       }
		       psor->dtype |= M_HIGH;

		       goto highlow;

	       case OPLOW:
		       if (psor->dtype & M_RCONST)
			       psor->doffset &= 0xFF;

		       psor->dtype |= M_LOW;

	       highlow:
		       psor->dsize = 1;
		       if ((!(psor->dflag & XTERNAL && psor->dtype & M_EXPLOFFSET))
			 && psor->dsegment
			 && (psor->dtype & (M_EXPLOFFSET | M_SEGRESULT
			     | M_REGRESULT | M_GROUPSEG | M_DATA | M_CODE)))
			       errorc (E_CXP);
		       break;

	       case OPOFFSET:
		       psor->fixtype = FOFFSET;

		       if (!(psor->dsegment || psor->dflag == XTERNAL))
			   errorc(E_OSG|E_WARN2);

		       if (!(M_DATA & psor->dtype))
			       psor->dcontext = NULL;
		       psor->dtype =
			   (psor->dtype |
			    M_RCONST | M_EXPLOFFSET) & ~(M_SEGRESULT);

		       if (fSimpleSeg)
			   makeGrpRel (psor);

		       /* preserve OFFSET arg size it's a const */
		       if ((psor->dsegment ||
			    psor->dcontext ||
			    psor->dflag == XTERNAL) &&
			   !(M_PTRSIZE & psor->dtype))
			       psor->dsize = 0;
		       break;
	       case OPLENGTH:
	       case OPSIZE:
		       /* Must be data associated */
		       valcheck (CDATA, TRUE, &a);
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);
		       if (a.stkoper == OPLENGTH)
			       psor->doffset = psor->dlength;
		       else
			       psor->doffset =
				  psor->dsize * psor->dlength;

		       psor->dflag &= ~XTERNAL;
		       break;
	       case OPTYPE:
		       a.right = psor->dsize;
		       oblititem (a.valright);
		       a.valright = defaultdsc ();
		       psor = &(a.valright->dsckind.opnd);
		       psor->doffset = a.right;
		       a.p->p->base = 0;
		       a.p->p->index = 0;
		       break;
	       case OPMASK:
	       case OPWIDTH:
		       /* Must be record or field */
		       valcheck (CREC, TRUE, &a);
		       if (psor->dextptr && psor->dflag != XTERNAL) {
			   if (a.stkoper == OPWIDTH)
			       if (psor->dextptr->symkind == REC)
				   psor->doffset = psor->dextptr->length;
			       else
				   psor->doffset = psor->dextptr->symu.rec.recwid;
			   else if (psor->dextptr->symkind == REC)
			       psor->doffset = psor->dextptr->offset;
			   else
			       psor->doffset = psor->dextptr->symu.rec.recmsk;
		       }
		       break;
	       case OPSTYPE:
		       a.right = 0;
		       if (errorcode == 0) {
			    if (psor->dflag == XTERNAL)
				    a.right |= 0x80;		/* external */
			    if (psor->dflag != UNDEFINED)
				    a.right |= 0x20;		/* defined */
			    if (psor->dtype & M_DATA)
				    a.right |= 0x02;		/* data */
			    if (psor->dtype & M_CODE)
				    a.right |= 0x01;		/* program */

			    if ((a.p->p->base == 0) && (a.p->p->index == 0)) {

				if (psor->dtype == xltsymtoresult[REGISTER])
				    a.right |= 0x10;		/* register */
				else if (psor->dtype & M_RCONST)
				    a.right |= 0x04;		/* constant */
				else if (psor->dtype & M_DATA)
				    a.right |= 0x08;		/* direct */

			    } else {
				a.p->p->base = 0;
				a.p->p->index = 0;
			    }
		       }
		       oblititem (a.valright);
		       a.valright = defaultdsc ();
		       psor = &(a.valright->dsckind.opnd);
		       psor->doffset = a.right;
		       errorcode = 0;
		       break;
	       case OPLPAR:
	       case OPLBRK:
		       if (!(a.p->parenflag || a.p->p->exprdone))
			       pushpar (a.p);
		       else if (a.stkoper == OPLBRK)
			       a.valright = regcheck (a.valright, FALSE, &a);
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);
		       break;
	       case OPMOD:
		       valcheck (CALLABS, FALSE, &a);
		       if (a.right == 0) {
			       /* div 0 */
			       errorc (E_DVZ);
			       psor->doffset = 0;
			       psor->dsign = FALSE;
		       }
		       else {
			       psor->doffset = a.left % a.right;
			       if (psor->doffset == 0 || !psol->dsign)
				       psor->dsign = FALSE;
			       else
				       psor->dsign = TRUE;
		       }
		       break;
	       case OPTHIS:
		       valcheck (CLSIZE, TRUE, &a);
		       /* Unary, right is size */
		       psor->s = 0;
		       psor->dsize = a.right;
		       psor->doffset = pcoffset;
		       psor->dsegment = pcsegment;
		       if (a.right >= CSFAR_LONG)
			       psor->dcontext = regsegment[CSSEG];
		       break;
	       case OPSHORT:
		       valcheck (CCODE, TRUE, &a);
		       /* Unary, must be code */
		       psor->dtype |= M_SHRT;
		       break;
	       case OPPTR:
		       valcheck (CLSIZE, FALSE, &a);
		       if (psol->doffset >= CSFAR_LONG &&
			  (M_RCONST == psor->dtype ||
			  (psor->dcontext && (M_DATA&psor->dtype && !(M_CODE&psor->dtype))) ))

			       errorc (E_NSO);		    /* Can't code_data */
		       else {
			       psor->dsize = a.left;
			       if ((M_DATA & psol->dtype)
				   && !(M_DATA & psor->dtype))
				       psor->dcontext = NULL;
			       /* Change code/data */
			       psor->dtype =
				    (psor->dtype & ~(M_CODE | M_DATA) |
				    (psol->dtype & (M_CODE | M_DATA))) &
				    ~(M_FORTYPE) | (M_PTRSIZE);
		       }
		       break;
	       case OPEQ:
	       case OPGE:
	       case OPGT:
	       case OPLE:
	       case OPLT:
	       case OPNE:
		       valcheck (CSAME, FALSE, &a);
		       signadjust (TRUE, &a);
		       /* Do signed R=L-R */
		       psol = &(a.valleft->dsckind.opnd);
		       psor = &(a.valright->dsckind.opnd);

		       if (!fArth32)
			   a.right &= 0xffff;

		       switch (a.stkoper) {
			       case OPEQ:
				       a.right = (a.right == 0);
				       break;
			       case OPGE:
				       a.right = !psor->dsign;
				       break;
			       case OPGT:
				       a.right = (!psor->dsign && a.right);
				       break;
			       case OPLE:
				       a.right = (psor->dsign || a.right == 0);
				       break;
			       case OPLT:
				       a.right = psor->dsign;
				       break;
			       case OPNE:
				       a.right = (a.right != 0);
				       break;
		       }
		       /*  Set Dsign if result TRUE */
		       psor->doffset = a.right;
		       psor->dsign = (a.right == 1);
		       psor->dcontext = NULL;
		       oblititem (a.valleft);
		       a.valleft = NULL;
		       break;
	       case OPCOLON:
		       /* <segment> : <var> */
		       valcheck (CLSEG, FALSE, &a);

		       if  ((a.p->p->bracklevel || a.p->evalop == OPLBRK) &&
			   (M_REGRESULT & (psol->dtype | psor->dtype)))
			   errorc(E_ISR);

		       psor->dtype = (psor->dtype|M_EXPLCOLON|M_DATA) & ~M_RCONST;

		       if (psol->dsegment) {

			   if (psol->dsegment->symkind == GROUP)
			       psor->dtype |= M_GROUPSEG;

			   if (!psor->dsegment &&
			       !(M_REGRESULT & psol->dtype) &&
			       !(a.p->p->base || a.p->p->index))

			       psor->dsegment = psol->dsegment;
		       }

		       psor->dcontext = psol->dsegment;
		       break;

	    } /* operator case */

	    if (!inset (a.stkoper, parseset)) {

		/* Have constant or segment result */

		psor->dlength = 0;

		psor->dsize = 0;
		psor->sized = 0;
		if (a.valleft)
			psol->dsize = 0;

		/* Have constant result( typeless ) */

		if (a.stkoper != OPSEG) {

		    psor->dtype = (psor->dtype & M_FORTYPE) | M_RCONST;
		    psor->dsegment = NULL;

		    if (a.valleft)
			psol->dtype &= ~M_PTRSIZE;
		}
	    }
	    a.p->p->curresult = a.valright;
	    psor = &(a.p->p->curresult->dsckind.opnd);

	    if (!fArth32 && optyp != TDD)
		psor->doffset &= 0xffff;

	    if (a.valleft) {
		/* Might need to copy some info */

		/* Prevent OPERATORs like +, -, . from
		losing the [DATA] flag if it it is the
		Left operand. This is ok, except when
		surrounded by a PTR which will drop
		segment override if not data type */

		if (a.stkoper != OPCOLON)
			psor->dtype |= psol->dtype & (M_DATA | M_CODE);
		if (psor->dflag == KNOWN)
			psor->dflag = psol->dflag;
		if (!psor->dcontext)
			psor->dcontext = psol->dcontext;
		if (psor->dsize == 0)
			psor->dsize = psol->dsize;
		if (psor->fixtype == FCONSTANT)
			psor->fixtype = psol->fixtype;

		psor->dtype |= psol->dtype & (M_PTRSIZE|M_EXPLOFFSET|M_FORTYPE);
		/* Above makes sure PTR or OFFSET is not lost */
		oblititem (a.valleft);
		a.valleft = NULL;
	    }
	}
	else {	/* no operator case */

	    a.p->p->curresult = a.valright;
	    psor = &(a.p->p->curresult->dsckind.opnd);
	    a.p->parenflag = FALSE;
	}

	if (!a.p->p->lastitem) {
	    a.p->p->lastprec = 0;
	    a.p->p->curresult->prec = 0;
	}
	else if (a.p->p->lastitem->itype == OPERATOR) {

	    if ((a.p->p->lastitem->dsckind.opr.oidx == OPLBRK) ||
		(a.p->p->lastitem->dsckind.opr.oidx == OPLPAR))

		/* Stop evaluating back at paren */
		a.p->p->lastprec = 0;

	    else {
		a.p->p->lastprec = a.p->p->lastitem->prec;
		if ((a.p->p->lastitem->dsckind.opr.oidx == OPUNPLUS) ||
		    (a.p->p->lastitem->dsckind.opr.oidx == OPUNMINUS))
			/* Force eval */
			a.p->p->lastitem->prec = a.p->p->lastprec = 20;
	    }
	}
	else
	    a.p->p->lastprec = a.p->p->lastitem->prec;

	if (itemptr) {
	    oblititem (itemptr);
	    itemptr = NULL;
	}

	/* Hook rest of list in */

	a.p->p->curresult->previtem = a.p->p->lastitem;
	a.p->p->lastitem = a.p->p->curresult;

	/* Push result back on */

	if (!a.p->p->curresult->previtem && a.p->p->exprdone)
	    a.p->p->lastitem = NULL;
}




/***	evaluate - evaluate stack
 *
 *	routine ();
 *
 *	Entry
 *	Exit
 *	Returns
 *	Calls
 */


VOID PASCAL CODESIZE
evaluate (
	struct ar *p
){
	struct evalrec	a;
	a.p = p;
	a.parenflag = FALSE;
	a.evalop = OPNOTHING;
	/* No paren or match to find */
	a.curoper = itemptr;

	if (a.curoper)
	    a.parenflag = !a.p->exprdone &&
			   (a.curoper->dsckind.opr.oidx == OPRPAR ||
			    a.curoper->dsckind.opr.oidx == OPRBRK);
	if (a.parenflag)
	    a.evalop = (a.curoper->dsckind.opr.oidx == OPRPAR)? OPLPAR: OPLBRK;

	do {	/* Evaluate to OPERATOR */

		evaltop (&a);

	} while (a.p->lastitem && a.p->lastitem->previtem &&
		 (a.p->exprdone ||
		  (!a.parenflag && a.p->lastprec >= a.p->curprec ) ||
		  ( a.parenflag && a.idx != a.evalop)) );

	/* stop if just value on expression stack */
	itemptr = a.curoper;
	if (a.p->lastprec == 0)
		a.p->lastprec = a.p->curresult->prec;

	if (!a.p->exprdone)
	    if (a.parenflag) {/* Push value and set prec */

		if (!a.p->lastitem->previtem)/* start of expr */
			a.p->lastprec = 0;
		else
			a.p->lastprec = a.p->lastitem->previtem->prec;

		/* Restore preced */
		a.p->lastitem->prec = a.p->lastprec;
		oblititem (itemptr);
		itemptr = NULL;

		/* Destroy close paren */
	    }
	    else {	    /* Case 1, OPERATOR eval */
		itemptr->previtem = a.p->lastitem;
		a.p->lastitem = itemptr;

		/* Push OPERATOR */
		if (a.p->lastprec != 20)
			a.p->lastprec = itemptr->prec;
	    }
}

/* Return a descriptor record to help instruction routines
	  generate the right code. The items are as follows:

		mode::	Value 0..4 Corresponds to 8086 mod

			0	No displacement unless rm=6 in which
				case this is direct mode with 2 bytes.
				( Arg is code or data, no indexing )

			1	Memory, 8 bit sign extended displace-
				ment.( Using indexing, Rconst )

			2	Memory, 16 bit displacement.( Using
				indexing, Rconst type )

			3	Register, rm is register code, not
				indexing mode.( Was REGresult )

			4	Immediate mode.( arg was Rconst, no
				indexing )

			386 modes are represented in an analogous way:
			
			3	Register, rm is register code, as above

			4	Immediate, as above

			5	No displacement indirect, unless rm=5,
				in which case this is a direct mode with
				4 byte offset.

			6	Memory, 8 bit signed displacement

			7	Memory, 32 bit signed displacement

			similarly, scaled modes are indicated with
			the next group.  if mode > 7, then rm contains
			the value of the Scaled Index Byte (SIB) and
			rm is implicitly 4.

			8	No displacement indirect, unless rm=5,
				in which case this is a direct mode with
				4 byte offset.

			9	Memory, 8 bit signed displacement

			10	Memory, 32 bit signed displacement

		rm   :: Value 0..7 Corresponds to 8086 or 80386 r/m

		      Value	Register	Index		386 index
			0	AX  AL	EAX	[BX][SI]	[EAX]
			1	CX  CL	ECX	[BX][DI]	[ECX]
			2	DX  DL	EDX	[BP][SI]	[EDX]
			3	BX  BL	EBX	[BP][DI]	[EBX]
			4	SP  AH	ESP	[SI]		not implemented
			5	BP  CH	EBP	[DI]		Direct or [EBP]
			6	SI  DH	ESI	Direct or [BP]	[ESI]
			7	DI  BH	EDI	[BX]		[EDI]

			Ridx contained pointer to index reg( DI | SI )
			Rbas contained pointer to base	reg( BX | BP )
			Both were NIL if no indexing.
			386 registers have 8 added to them while in
			the ar structure's base and index fields.
			this is so we can tell eax from no register
			at all.


		w    :: Boolean  Corresponds to 8086 w flag. TRUE if
			word mode, FALSE if byte mode.

		s    :: TRUE if value is -128..+127
		Dsize	::	Size of var/label or PTR value


		FIXtype ::	Type of fixup to feed to EMITxxx
				routines:

				Fpointer	Label is FAR
				Foffset 	Word, not constant
				Fbaseseg	SEG or seg/group name
				Fgroupseg	Offset to group
				Fconstant	Immediate data
				Fhigh		Take high of offset
				Flow		Take low of offset
				Fnone		No fixup( register )

		Dtype	::	Kind of value. Seg,group, const, Data
		Dflag	::	Value attr, undef,?,extern,forw,...
		Doffset ::	16 bit value of result

		Dsegment::	Copy of Dsegment. Pointer to segment of
				result. If NIL, is constant. Will point
				to segment name or possibly name of
				external if external with no segment.

		Dcontext::	Copy of Dcontext. Pointer to segment
				from which to calculate offset. If :
				OPERATOR used, Dcontext will be left
				arg. If result is code label, will be
				CS assume at time of label define. Else
				will be NIL and then filled in with
				segment register assume that contains
				Dsegment.

		seg ::		Segment register of override. If none
				given, will be 4. If register is not
				known, will be 5.
 */