[unix-history] / usr / src / old / as.vax / asjxxx.c

/* Copyright (c) 1980 Regents of the University of California */
static	char sccsid[] = "@(#)asjxxx.c 4.2 %G%";
#include	<stdio.h>
#include	"as.h"
#include	"assyms.h"

#define JBR 0x11
#define BRW 0x31

/*
 *	The number of bytes to add if the jxxx must be "exploded"
 *	into the long form
 */
#define	JBRFSIZE	1	/*goes to brw*/
#define JXXXFSIZE	3	/*goes to brb, brw <byte> <byte> */

/*
 *	These variables are filled by asscan.c with the
 *	last name encountered (a pointer buried in the intermediate file),
 *	and the last jxxx symbol table entry encountered.
 */
struct 	symtab	*lastnam;
struct	symtab	*lastjxxx;

/*
 *	Handle jxxx instructions
 */
ijxout(op,ap,nact)
	struct arg *ap;
{
	if (passno == 1){
		/*
		 *	READ THIS BEFORE LOOKING AT jxxxfix()
		 *
		 *	Record the jxxx in a special symbol table entry
		 */
		register struct symtab *jumpfrom;

		/*
		 *	We assume the MINIMAL length
		 */
		putins(op,ap,nact); 
		jumpfrom = lastjxxx;
		jumpfrom->s_tag = JXACTIVE;
		jumpfrom->s_jxbump = 0;
		if (op == JBR)
			jumpfrom->s_jxfear = JBRFSIZE;
		else
			jumpfrom->s_jxfear = JXXXFSIZE;
		if (lastnam == 0)
			yyerror("jxxx destination not a label");
		jumpfrom->s_dest = lastnam;
		jumpfrom->s_type = dotp->e_xtype;	/*only TEXT or DATA*/
		jumpfrom->s_index = dotp-usedot;
		/*
		 *	value ALWAYS (ALWAYS!!!) indexes the next instruction
		 *	after the jump, even in the jump must be exploded
		 *	(bumped)
		 */
		jumpfrom->s_value = dotp->e_xvalue;
		njxxx++;
	} else {/* pass2, resolve */
		/*
		 *	READ THIS AFTER LOOKING AT jxxxfix()
		 */
		register long		oxvalue;
		register struct	exp 	*xp; 
		register struct symtab	*tunnel;
		register struct arg	*aplast;

		aplast = ap + nact - 1;
		xp = aplast->a_xp;
		if (lastjxxx->s_tag == JXTUNNEL){
			lastjxxx->s_tag = JXINACTIVE;
			tunnel = lastjxxx->s_dest;
			xp->e_xvalue = tunnel->s_value	/*index of instruction following*/
				    - 3			/* size of brw + word*/
				    + ( ( (tunnel->s_jxfear == JBRFSIZE) &&
					  (tunnel->s_jxbump == 0))?1:0);
							/*non bumped branch byteis only 2 back*/
		}
		if (lastjxxx->s_jxbump == 0){	/*wasn't bumped, so is short form*/
			putins(op, ap, nact);
		} else {
			if (op != JBR){	/*branch reverse conditional byte over 
					  branch unconditional word*/
				oxvalue = xp->e_xvalue;
				xp->e_xvalue = lastjxxx->s_value;
				putins(op^1, ap, nact);
				xp->e_xvalue = oxvalue;
			}
			putins(BRW, aplast, 1);
		}
	}
}	/*end of ijxout*/

jalign(xp, sp)
	register struct exp *xp;
	register struct symtab *sp;
{
	register	int	mask;
	if (xp->e_xtype != XABS || xp->e_xvalue < 0 || xp->e_xvalue > 16) {
		yyerror("Illegal `align' argument");
		return;
	}
	flushfield(NBPW/4);
	if (passno == 1) {
		sp->s_tag = JXALIGN;
		sp->s_jxfear = (1 << xp->e_xvalue) - 1;
		sp->s_type = dotp->e_xtype;
		sp->s_index = dotp-usedot;
		/*
		 *	We guess that the align will take up at least one
		 *	byte in the code output.  We will correct for this
		 *	initial high guess when we explode (bump) aligns
		 *	when we fix the jxxxes.  We must do this guess
		 *	so that the symbol table is sorted correctly
		 *	and labels declared to fall before the align
		 *	really get their, instead of guessing zero size
		 *	and have the label (incorrectly) fall after the jxxx.
		 *	This is a quirk of our requirement that indices into
		 *	the code stream point to the next byte following
		 *	the logical entry in the symbol table
		 */
		dotp->e_xvalue += 1;
		sp->s_value = dotp->e_xvalue;
		njxxx++;
	} else {
		mask = (1 << xp->e_xvalue) - 1;
		while (dotp->e_xvalue & mask){
#ifdef UNIX
			outb(0);
#endif UNIX
#ifdef VMS
			*vms_obj_ptr++ = -1;
			*vms_obj_ptr++ = 0;
			dotp->e_xvalue += 1;
#endif VMS
		}
	}
}

/*
 *	Pass 1.5, resolve jxxx instructions and .align in .text
 */
jxxxfix() 
{
	register struct symtab 	*jumpfrom;
		 struct symtab	**cojumpfrom, *ubjumpfrom;
	register struct symtab 	*dest;
	register struct symtab	*intdest;	/*intermediate dest*/
	register struct symtab	**cointdest, *ubintdest;

	register struct symtab 	*tunnel;
	 	 int 		displ,nchange;
		 int		badjxalign;	/*if jump across an align*/
		 int		stillactives;	/*if still active jxxxes*/
		 int		segno;		/*current segment number*/
		 int		topono;		/*which iteration in the topo sort*/
	register unsigned char	tag;
	/*
	 *	consider each segment in turn...
	 */
	for (segno = 0; segno < NLOC + NLOC; segno++){
	    badjxalign = 0;		/*done on a per segment basis*/
	    /*
	     *	Do a lazy topological sort.
	     */
	    for (topono = 1, nchange = 1; nchange != 0; topono++){
#ifdef DEBUG
		if (debug)
			printf("\nSegment %d, topo iteration %d\n",
				segno, topono);
#endif
		nchange = 0;
		stillactives = 0;
		/*
		 *	We keep track of one possible tunnel location.
		 *	A tunnel will eventually be an unconditional
		 *	branch to the same place that another jxxx
		 *	will want to branch to.  We will turn a
		 *	branch conditional/unconditional (word) that would
		 *	have to get bumped because its destination is too
		 *	far away, into a branch conditional/unconditional
		 *	byte to the tunnel branch conditional/unconditional.
		 *	Of course, the tunnel must branch to the same place
		 *	as we want to go.
		 */
		tunnel = 0;	/*initially, no tunnel*/
		SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom, ubjumpfrom, ++){
			tag = jumpfrom->s_tag;
			if (tag <= IGNOREBOUND)
				continue;	/*just an ordinary symbol*/
			if (tag == JXALIGN){
				tunnel = 0;	/*avoid tunneling across a flex alocation*/
				continue;	/*we take care of these later*/
			}
			if (   jumpfrom->s_jxfear == JBRFSIZE	/*unconditional*/
			    || (   tag == JXINACTIVE		/*inactive bumped*/
				&& (jumpfrom->s_jxbump != 0)
			       )
			   ) tunnel = jumpfrom;
			if (tag != JXACTIVE)
				continue;
			dest = jumpfrom->s_dest;
			if (jumpfrom->s_index != dest->s_index){
				yyerror("Intersegment jxxx");
				continue;
			}
			displ = dest->s_value - jumpfrom->s_value;
			if (displ < MINBYTE || displ > MAXBYTE) {
				/*
				 *	This is an immediate lose!
				 *
				 *	We first attempt to tunnel
				 *	by finding an intervening jump that
				 *	has  the same destination.
				 *	The tunnel is always the first preceeding
				 *	jxxx instruction, so the displacement
				 *	to the tunnel is less than zero, and
				 *	its relative position will be unaffected
				 *	by future jxxx expansions.
				 */
				if (    (jumpfrom->s_jxfear > JBRFSIZE)
				     && (tunnel) 
				     && (tunnel->s_dest == jumpfrom->s_dest)	
				     && (tunnel->s_index == jumpfrom->s_index)
				     && (tunnel->s_value - jumpfrom->s_value >=
						MINBYTE + JXXXFSIZE)
				   ) {
						/*
						 *	tunnelling is OK
						 */
						jumpfrom->s_dest = tunnel;
						/*
						 * no bumping needed, this
						 * is now effectively inactive
						 * but must be remembered
						 */
						jumpfrom->s_tag = JXTUNNEL;
#ifdef DEBUG
						if(debug)
						printf("Tunnel from %s from line %d\n",
							jumpfrom->s_name, lineno);
#endif
						continue;
				} else {	/*tunneling not possible*/
					/*
					 *	since this will be turned
					 *	into a bumped jump, we can
					 *	use the unconditional jump
					 *	as a tunnel
					 */
					tunnel = jumpfrom;
					jumpfrom->s_tag = JXNOTYET;
					++nchange;
					continue;
				}
			}	/*end of immediate lose*/
			/*
			 *	Do a forward search for an intervening jxxx
			 */
			if (displ >= 0) {
				SEGITERATE(segno, cojumpfrom + 1,0,cointdest,
						intdest, ubintdest, ++){
					if (intdest->s_value > dest->s_value) 
						break; /* beyond destination */
					if (intdest->s_tag <= JXQUESTIONABLE)
						continue;	/*frozen solid*/
					if (intdest->s_tag == JXALIGN){
						jumpfrom->s_jxoveralign = 1;
						badjxalign++;
					}
					/*
					 *	we assume the worst case
					 *	for unfrozen jxxxxes
					 */
					displ += intdest->s_jxfear;
				}
				if (displ <= MAXBYTE){
					/*
					 *	the worst possible conditions
					 *	can't hurt us, so forget about
					 *	this jump
					 */
					jumpfrom->s_tag = JXINACTIVE;
				} else {
					stillactives++;
				}
			} else {
			/*
			 *	backward search for intervening jxxx
			 */
				SEGITERATE(segno, cojumpfrom - 1,1,cointdest,
				  intdest, ubintdest, --){
					if (intdest->s_value <= dest->s_value) 
						break; /* beyond destination */
					if (intdest->s_tag <= JXQUESTIONABLE)
						continue;	/*frozen solid*/
					if (intdest->s_tag == JXALIGN){
						jumpfrom->s_jxoveralign = 1;
						badjxalign++;
					}
					displ -= intdest->s_jxfear; 
				}
				if (displ >= MINBYTE) {
					jumpfrom->s_tag = JXINACTIVE;
				} else {
					stillactives++;
				}
			}	/*end of backwards search*/
		}	/*end of iterating through all symbols in this seg*/

		if (nchange == 0) {
			/*
			 *	Now, if there are still active jxxx entries,
			 *	we are partially deadlocked.  We can leave
			 *	these jxxx entries in their assumed short jump
			 *	form, as all initial displacement calcualtions
			 *	are hanging on unresolved jxxx instructions
			 *	that might explode into a long form, causing
			 *	other jxxxes jumping across the first set of
			 *	jxxxes to explode, etc.
			 *	However, if a jxxx jumps across a .align,
			 *	we assume the worst for the deadlock cycle,
			 *	and resolve all of them towards the long
			 *	jump.
			 *	Currently, the C compiler does not produce
			 *	jumps across aligns, as aligns are only used
			 *	in data segments, or in text segments to align
			 *	functions.
			 */
			if (stillactives){
				SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom,
				    ubjumpfrom, ++){
					if (jumpfrom->s_tag == JXACTIVE){
						jumpfrom->s_tag =
						  badjxalign?JXNOTYET:JXINACTIVE;
					}
				}
				if (badjxalign){
					jxxxbump(segno, (struct symtab **)0);
				}
			}
			/*
			 *	Handle  all of the .align s
			 */
			SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom,
			   ubjumpfrom, ++){
			    if (jumpfrom->s_tag == JXALIGN){
				/*
				 *	Predict the true displacement
				 *	needed, irregardless of the
				 *	fact that we guessed 1
				 */
				displ = (jumpfrom->s_value - 1) & (unsigned)jumpfrom->s_jxfear;
				if (displ == 0){	/*no virtual displacement*/
					jumpfrom->s_jxfear = -1;
				} else {
					jumpfrom->s_jxfear = (jumpfrom->s_jxfear + 1) - displ;
					/*
					 *	assert jumpfrom->s_jxfear > 0
					 */
					if (jumpfrom->s_jxfear == 1){
						/*our prediction was correct*/
						continue;
					}
					/*
					 *	assert jumpfrom->s_jxfear > 1
					 */
					jumpfrom->s_jxfear -= 1;	/*correct guess*/
				}
				/*
				 *	assert jumpfrom->s_jxfear = -1, +1...2**n-1
				 */
				jumpfrom->s_tag = JXNOTYET;	/*signal*/
				jxxxbump(segno, cojumpfrom);
				jumpfrom->s_tag = JXINACTIVE;
				/*
				 *	Assert jxfrom->jxvalue indexes the first
				 *	code byte after the added bytes, and
				 *	has n low order zeroes.
				 */
			  }
			}	/*end of walking through each segment*/
	    	}	/*end of no changes */
		else {	/*changes, and still have to try another pass*/
			jxxxbump(segno, (struct symtab **)0);
		}
	   }	/*end of doing the topologic sort*/
	}	/*end of iterating through all segments*/
}	/*end of jxxxfix*/

/*
 *	Go through the symbols in a given segment number,
 *	and see which entries are jxxx entries that have
 *	been logically "exploded" (expanded), but for which
 *	the value of textually following symbols has not been
 *	increased
 */

jxxxbump(segno, starthint)
	int	segno;
	struct	symtab **starthint;
{
	register	struct	symtab	**cosp, *sp;
	register	struct	symtab		*ub;
	register	int	cum_bump;
	register	unsigned	char	tag;

	cum_bump = 0;
	SEGITERATE(segno, starthint, 0, cosp, sp, ub, ++){
		tag = sp->s_tag;
		if (tag == JXNOTYET){
#ifdef DEBUG
			if (debug){
			if (sp->s_dest != 0)
				printf("Explode jump to %s on line %d\n",
					sp->s_dest->s_name, lineno);
			else
				printf("Explode an align!\n");
			}
#endif
			sp->s_tag = JXINACTIVE;
			sp->s_jxbump = 1;
			cum_bump += sp->s_jxfear;
		}
		/*
		 *	Only bump labels and jxxxes. Ignored entries can
		 *	be incremented, as they are thrown away later on.
		 *	Stabds are given their final value in the second 
		 *	pass.
		 */
		if (tag >= OKTOBUMP)	/*only bump labels and jxxxes and floating stabs*/
			sp->s_value += cum_bump;
	}
	usedot[segno].e_xvalue += cum_bump;
}
Commit	Line	Data
d0d638ee	1	/* Copyright (c) 1980 Regents of the University of California */
451260e7	2	static char sccsid[] = "@(#)asjxxx.c 4.2 %G%";
d0d638ee	3	#include <stdio.h>
d0d638ee BJ	4	#include "as.h"
	5	#include "assyms.h"
	6
	7	#define JBR 0x11
	8	#define BRW 0x31
	9
	10	/*
	11	* The number of bytes to add if the jxxx must be "exploded"
	12	* into the long form
	13	*/
	14	#define JBRFSIZE 1 /goes to brw/
	15	#define JXXXFSIZE 3 /goes to brb, brw <byte> <byte> /
	16
	17	/*
	18	* These variables are filled by asscan.c with the
	19	* last name encountered (a pointer buried in the intermediate file),
	20	* and the last jxxx symbol table entry encountered.
	21	*/
	22	struct symtab *lastnam;
	23	struct symtab *lastjxxx;
	24
	25	/*
	26	* Handle jxxx instructions
	27	*/
	28	ijxout(op,ap,nact)
	29	struct arg *ap;
	30	{
	31	if (passno == 1){
	32	/*
	33	* READ THIS BEFORE LOOKING AT jxxxfix()
	34	*
	35	* Record the jxxx in a special symbol table entry
	36	*/
	37	register struct symtab *jumpfrom;
	38
	39	/*
	40	* We assume the MINIMAL length
	41	*/
	42	putins(op,ap,nact);
	43	jumpfrom = lastjxxx;
451260e7 RH	44	jumpfrom->s_tag = JXACTIVE;
451260e7 RH	45	jumpfrom->s_jxbump = 0;
d0d638ee	46	if (op == JBR)
451260e7	47	jumpfrom->s_jxfear = JBRFSIZE;
d0d638ee	48	else
451260e7	49	jumpfrom->s_jxfear = JXXXFSIZE;
d0d638ee BJ	50	if (lastnam == 0)
d0d638ee BJ	51	yyerror("jxxx destination not a label");
451260e7 RH	52	jumpfrom->s_dest = lastnam;
	53	jumpfrom->s_type = dotp->e_xtype; /only TEXT or DATA/
	54	jumpfrom->s_index = dotp-usedot;
d0d638ee BJ	55	/*
	56	* value ALWAYS (ALWAYS!!!) indexes the next instruction
	57	* after the jump, even in the jump must be exploded
	58	* (bumped)
	59	*/
451260e7	60	jumpfrom->s_value = dotp->e_xvalue;
d0d638ee BJ	61	njxxx++;
	62	} else {/* pass2, resolve */
	63	/*
	64	* READ THIS AFTER LOOKING AT jxxxfix()
	65	*/
	66	register long oxvalue;
	67	register struct exp *xp;
	68	register struct symtab *tunnel;
	69	register struct arg *aplast;
	70
	71	aplast = ap + nact - 1;
451260e7 RH	72	xp = aplast->a_xp;
	73	if (lastjxxx->s_tag == JXTUNNEL){
	74	lastjxxx->s_tag = JXINACTIVE;
	75	tunnel = lastjxxx->s_dest;
	76	xp->e_xvalue = tunnel->s_value /index of instruction following/
d0d638ee	77	- 3 /* size of brw + word*/
451260e7 RH	78	+ ( ( (tunnel->s_jxfear == JBRFSIZE) &&
451260e7 RH	79	(tunnel->s_jxbump == 0))?1:0);
d0d638ee BJ	80	/non bumped branch byteis only 2 back/
d0d638ee BJ	81	}
451260e7	82	if (lastjxxx->s_jxbump == 0){ /wasn't bumped, so is short form/
d0d638ee BJ	83	putins(op, ap, nact);
	84	} else {
	85	if (op != JBR){ /*branch reverse conditional byte over
	86	branch unconditional word*/
451260e7 RH	87	oxvalue = xp->e_xvalue;
451260e7 RH	88	xp->e_xvalue = lastjxxx->s_value;
d0d638ee	89	putins(op^1, ap, nact);
451260e7	90	xp->e_xvalue = oxvalue;
d0d638ee BJ	91	}
	92	putins(BRW, aplast, 1);
	93	}
	94	}
	95	} /end of ijxout/
	96
	97	jalign(xp, sp)
	98	register struct exp *xp;
	99	register struct symtab *sp;
	100	{
	101	register int mask;
451260e7	102	if (xp->e_xtype != XABS \|\| xp->e_xvalue < 0 \|\| xp->e_xvalue > 16) {
d0d638ee BJ	103	yyerror("Illegal `align' argument");
	104	return;
	105	}
	106	flushfield(NBPW/4);
	107	if (passno == 1) {
451260e7 RH	108	sp->s_tag = JXALIGN;
	109	sp->s_jxfear = (1 << xp->e_xvalue) - 1;
	110	sp->s_type = dotp->e_xtype;
	111	sp->s_index = dotp-usedot;
d0d638ee BJ	112	/*
	113	* We guess that the align will take up at least one
	114	* byte in the code output. We will correct for this
	115	* initial high guess when we explode (bump) aligns
	116	* when we fix the jxxxes. We must do this guess
	117	* so that the symbol table is sorted correctly
	118	* and labels declared to fall before the align
	119	* really get their, instead of guessing zero size
	120	* and have the label (incorrectly) fall after the jxxx.
	121	* This is a quirk of our requirement that indices into
	122	* the code stream point to the next byte following
	123	* the logical entry in the symbol table
	124	*/
451260e7 RH	125	dotp->e_xvalue += 1;
451260e7 RH	126	sp->s_value = dotp->e_xvalue;
d0d638ee BJ	127	njxxx++;
d0d638ee BJ	128	} else {
451260e7 RH	129	mask = (1 << xp->e_xvalue) - 1;
451260e7 RH	130	while (dotp->e_xvalue & mask){
d0d638ee BJ	131	#ifdef UNIX
	132	outb(0);
	133	#endif UNIX
	134	#ifdef VMS
	135	*vms_obj_ptr++ = -1;
	136	*vms_obj_ptr++ = 0;
451260e7	137	dotp->e_xvalue += 1;
d0d638ee BJ	138	#endif VMS
	139	}
	140	}
	141	}
	142
	143	/*
	144	* Pass 1.5, resolve jxxx instructions and .align in .text
	145	*/
	146	jxxxfix()
	147	{
	148	register struct symtab *jumpfrom;
	149	struct symtab *cojumpfrom, ubjumpfrom;
	150	register struct symtab *dest;
	151	register struct symtab intdest; /intermediate dest*/
	152	register struct symtab *cointdest, ubintdest;
	153
	154	register struct symtab *tunnel;
	155	int displ,nchange;
	156	int badjxalign; /if jump across an align/
	157	int stillactives; /if still active jxxxes/
	158	int segno; /current segment number/
	159	int topono; /which iteration in the topo sort/
	160	register unsigned char tag;
	161	/*
	162	* consider each segment in turn...
	163	*/
	164	for (segno = 0; segno < NLOC + NLOC; segno++){
	165	badjxalign = 0; /done on a per segment basis/
	166	/*
	167	* Do a lazy topological sort.
	168	*/
	169	for (topono = 1, nchange = 1; nchange != 0; topono++){
	170	#ifdef DEBUG
	171	if (debug)
	172	printf("\nSegment %d, topo iteration %d\n",
	173	segno, topono);
	174	#endif
	175	nchange = 0;
	176	stillactives = 0;
	177	/*
	178	* We keep track of one possible tunnel location.
	179	* A tunnel will eventually be an unconditional
	180	* branch to the same place that another jxxx
	181	* will want to branch to. We will turn a
	182	* branch conditional/unconditional (word) that would
	183	* have to get bumped because its destination is too
	184	* far away, into a branch conditional/unconditional
	185	* byte to the tunnel branch conditional/unconditional.
	186	* Of course, the tunnel must branch to the same place
	187	* as we want to go.
	188	*/
	189	tunnel = 0; /initially, no tunnel/
	190	SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom, ubjumpfrom, ++){
451260e7	191	tag = jumpfrom->s_tag;
d0d638ee BJ	192	if (tag <= IGNOREBOUND)
	193	continue; /just an ordinary symbol/
	194	if (tag == JXALIGN){
	195	tunnel = 0; /avoid tunneling across a flex alocation/
	196	continue; /we take care of these later/
	197	}
451260e7	198	if ( jumpfrom->s_jxfear == JBRFSIZE /unconditional/
d0d638ee	199	\|\| ( tag == JXINACTIVE /inactive bumped/
451260e7	200	&& (jumpfrom->s_jxbump != 0)
d0d638ee BJ	201	)
	202	) tunnel = jumpfrom;
	203	if (tag != JXACTIVE)
	204	continue;
451260e7 RH	205	dest = jumpfrom->s_dest;
451260e7 RH	206	if (jumpfrom->s_index != dest->s_index){
d0d638ee BJ	207	yyerror("Intersegment jxxx");
	208	continue;
	209	}
451260e7	210	displ = dest->s_value - jumpfrom->s_value;
d0d638ee BJ	211	if (displ < MINBYTE \|\| displ > MAXBYTE) {
	212	/*
	213	* This is an immediate lose!
	214	*
	215	* We first attempt to tunnel
	216	* by finding an intervening jump that
	217	* has the same destination.
	218	* The tunnel is always the first preceeding
	219	* jxxx instruction, so the displacement
	220	* to the tunnel is less than zero, and
	221	* its relative position will be unaffected
	222	* by future jxxx expansions.
	223	*/
451260e7	224	if ( (jumpfrom->s_jxfear > JBRFSIZE)
d0d638ee	225	&& (tunnel)
451260e7 RH	226	&& (tunnel->s_dest == jumpfrom->s_dest)
	227	&& (tunnel->s_index == jumpfrom->s_index)
	228	&& (tunnel->s_value - jumpfrom->s_value >=
d0d638ee BJ	229	MINBYTE + JXXXFSIZE)
	230	) {
	231	/*
	232	* tunnelling is OK
	233	*/
451260e7	234	jumpfrom->s_dest = tunnel;
d0d638ee BJ	235	/*
	236	* no bumping needed, this
	237	* is now effectively inactive
	238	* but must be remembered
	239	*/
451260e7	240	jumpfrom->s_tag = JXTUNNEL;
d0d638ee BJ	241	#ifdef DEBUG
	242	if(debug)
	243	printf("Tunnel from %s from line %d\n",
451260e7	244	jumpfrom->s_name, lineno);
d0d638ee BJ	245	#endif
	246	continue;
	247	} else { /tunneling not possible/
	248	/*
	249	* since this will be turned
	250	* into a bumped jump, we can
	251	* use the unconditional jump
	252	* as a tunnel
	253	*/
	254	tunnel = jumpfrom;
451260e7	255	jumpfrom->s_tag = JXNOTYET;
d0d638ee BJ	256	++nchange;
	257	continue;
	258	}
	259	} /end of immediate lose/
	260	/*
	261	* Do a forward search for an intervening jxxx
	262	*/
	263	if (displ >= 0) {
	264	SEGITERATE(segno, cojumpfrom + 1,0,cointdest,
	265	intdest, ubintdest, ++){
451260e7	266	if (intdest->s_value > dest->s_value)
d0d638ee	267	break; /* beyond destination */
451260e7	268	if (intdest->s_tag <= JXQUESTIONABLE)
d0d638ee	269	continue; /frozen solid/
451260e7 RH	270	if (intdest->s_tag == JXALIGN){
451260e7 RH	271	jumpfrom->s_jxoveralign = 1;
d0d638ee BJ	272	badjxalign++;
	273	}
	274	/*
	275	* we assume the worst case
	276	* for unfrozen jxxxxes
	277	*/
451260e7	278	displ += intdest->s_jxfear;
d0d638ee BJ	279	}
	280	if (displ <= MAXBYTE){
	281	/*
	282	* the worst possible conditions
	283	* can't hurt us, so forget about
	284	* this jump
	285	*/
451260e7	286	jumpfrom->s_tag = JXINACTIVE;
d0d638ee BJ	287	} else {
	288	stillactives++;
	289	}
	290	} else {
	291	/*
	292	* backward search for intervening jxxx
	293	*/
	294	SEGITERATE(segno, cojumpfrom - 1,1,cointdest,
	295	intdest, ubintdest, --){
451260e7	296	if (intdest->s_value <= dest->s_value)
d0d638ee	297	break; /* beyond destination */
451260e7	298	if (intdest->s_tag <= JXQUESTIONABLE)
d0d638ee	299	continue; /frozen solid/
451260e7 RH	300	if (intdest->s_tag == JXALIGN){
451260e7 RH	301	jumpfrom->s_jxoveralign = 1;
d0d638ee BJ	302	badjxalign++;
d0d638ee BJ	303	}
451260e7	304	displ -= intdest->s_jxfear;
d0d638ee BJ	305	}
d0d638ee BJ	306	if (displ >= MINBYTE) {
451260e7	307	jumpfrom->s_tag = JXINACTIVE;
d0d638ee BJ	308	} else {
	309	stillactives++;
	310	}
	311	} /end of backwards search/
	312	} /end of iterating through all symbols in this seg/
	313
	314	if (nchange == 0) {
	315	/*
	316	* Now, if there are still active jxxx entries,
	317	* we are partially deadlocked. We can leave
	318	* these jxxx entries in their assumed short jump
	319	* form, as all initial displacement calcualtions
	320	* are hanging on unresolved jxxx instructions
	321	* that might explode into a long form, causing
	322	* other jxxxes jumping across the first set of
	323	* jxxxes to explode, etc.
	324	* However, if a jxxx jumps across a .align,
	325	* we assume the worst for the deadlock cycle,
	326	* and resolve all of them towards the long
	327	* jump.
	328	* Currently, the C compiler does not produce
	329	* jumps across aligns, as aligns are only used
	330	* in data segments, or in text segments to align
	331	* functions.
	332	*/
	333	if (stillactives){
	334	SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom,
	335	ubjumpfrom, ++){
451260e7 RH	336	if (jumpfrom->s_tag == JXACTIVE){
451260e7 RH	337	jumpfrom->s_tag =
d0d638ee BJ	338	badjxalign?JXNOTYET:JXINACTIVE;
	339	}
	340	}
	341	if (badjxalign){
	342	jxxxbump(segno, (struct symtab **)0);
	343	}
	344	}
	345	/*
	346	* Handle all of the .align s
	347	*/
	348	SEGITERATE(segno, 0, 0, cojumpfrom, jumpfrom,
	349	ubjumpfrom, ++){
451260e7	350	if (jumpfrom->s_tag == JXALIGN){
d0d638ee BJ	351	/*
	352	* Predict the true displacement
	353	* needed, irregardless of the
	354	* fact that we guessed 1
	355	*/
451260e7	356	displ = (jumpfrom->s_value - 1) & (unsigned)jumpfrom->s_jxfear;
d0d638ee	357	if (displ == 0){ /no virtual displacement/
451260e7	358	jumpfrom->s_jxfear = -1;
d0d638ee	359	} else {
451260e7	360	jumpfrom->s_jxfear = (jumpfrom->s_jxfear + 1) - displ;
d0d638ee	361	/*
451260e7	362	* assert jumpfrom->s_jxfear > 0
d0d638ee	363	*/
451260e7	364	if (jumpfrom->s_jxfear == 1){
d0d638ee BJ	365	/our prediction was correct/
	366	continue;
	367	}
	368	/*
451260e7	369	* assert jumpfrom->s_jxfear > 1
d0d638ee	370	*/
451260e7	371	jumpfrom->s_jxfear -= 1; /correct guess/
d0d638ee BJ	372	}
d0d638ee BJ	373	/*
451260e7	374	* assert jumpfrom->s_jxfear = -1, +1...2**n-1
d0d638ee	375	*/
451260e7	376	jumpfrom->s_tag = JXNOTYET; /signal/
d0d638ee	377	jxxxbump(segno, cojumpfrom);
451260e7	378	jumpfrom->s_tag = JXINACTIVE;
d0d638ee BJ	379	/*
	380	* Assert jxfrom->jxvalue indexes the first
	381	* code byte after the added bytes, and
	382	* has n low order zeroes.
	383	*/
	384	}
	385	} /end of walking through each segment/
	386	} /end of no changes /
	387	else { /changes, and still have to try another pass/
	388	jxxxbump(segno, (struct symtab **)0);
	389	}
	390	} /end of doing the topologic sort/
	391	} /end of iterating through all segments/
	392	} /end of jxxxfix/
	393
	394	/*
	395	* Go through the symbols in a given segment number,
	396	* and see which entries are jxxx entries that have
	397	* been logically "exploded" (expanded), but for which
	398	* the value of textually following symbols has not been
	399	* increased
	400	*/
	401
	402	jxxxbump(segno, starthint)
	403	int segno;
	404	struct symtab **starthint;
	405	{
	406	register struct symtab *cosp, sp;
	407	register struct symtab *ub;
	408	register int cum_bump;
	409	register unsigned char tag;
	410
	411	cum_bump = 0;
	412	SEGITERATE(segno, starthint, 0, cosp, sp, ub, ++){
451260e7	413	tag = sp->s_tag;
d0d638ee BJ	414	if (tag == JXNOTYET){
	415	#ifdef DEBUG
	416	if (debug){
451260e7	417	if (sp->s_dest != 0)
d0d638ee	418	printf("Explode jump to %s on line %d\n",
451260e7	419	sp->s_dest->s_name, lineno);
d0d638ee BJ	420	else
	421	printf("Explode an align!\n");
	422	}
	423	#endif
451260e7 RH	424	sp->s_tag = JXINACTIVE;
	425	sp->s_jxbump = 1;
	426	cum_bump += sp->s_jxfear;
d0d638ee BJ	427	}
	428	/*
	429	* Only bump labels and jxxxes. Ignored entries can
	430	* be incremented, as they are thrown away later on.
	431	* Stabds are given their final value in the second
	432	* pass.
	433	*/
	434	if (tag >= OKTOBUMP) /only bump labels and jxxxes and floating stabs/
451260e7	435	sp->s_value += cum_bump;
d0d638ee	436	}
451260e7	437	usedot[segno].e_xvalue += cum_bump;
d0d638ee	438	}