c20.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

				}
				align->pop = 0;
				align->refc = 0;
				align->ref = NULL;
				align->labno = 0;
				prev = align;
				n_aligns++;
			}
		}
		prev = prev->forw;
	}
}

output()
{
	register struct node *t;
	int casebas;

	t = &first;
	while (t = t->forw) switch (t->op) {

	case END:
		fflush(stdout);
		return;

	case LABEL:
		printf("L%d:", t->labno);
		continue;

	case DLABEL:
		printf("%s:", t->code);
		continue;

	case CASE:
		casebas=0;

	default: std:
		if (t->pop==0) {/* must find it */
			register struct optab *p;
			for (p=optab; p->opstring[0]; ++p)
				if (p->opcode==t->combop) {t->pop=p; break;}
		}
		printf("\t%s", t->pop->opstring);
		if (t->code) printf("\t%s", t->code);
		if (t->labno!=0) printf("%cL%d\n",
							(t->code ? ',' : '\t'),
							t->labno);
		else printf("\n");
		continue;

	case MOVA:
		if (t->labno==0) goto std;
		printf("mova%c\tL%d,%s\n","bwlq"[t->subop-BYTE],t->labno,t->code);
		continue;

	case JSW:
		if (t->subop!=0) {/* F77JSW */
			printf(".long\tL%d\n",t->labno); continue;
		}
		if (casebas==0) printf("L%d:\n",casebas=isn++);
		printf(".word	L%d-L%d\n", t->labno, casebas);
		continue;
 	case MOV:				/* 005 */
 		if (t->forw) if(t->forw->op == CBR) goto std;
 		if (*t->code == '$') goto std;
 		if (t->subop == FFLOAT)
 			{
 			printf("movl\t%s\n", t->code);
 			continue;
 			}
 		if (t->subop == DFLOAT || t->subop == GFLOAT)
 			{
 			printf("movq\t%s\n", t->code);
 			continue;
 			}
 		if (t->subop == HFLOAT)
 			{
 			printf("movo\t%s\n", t->code);
 			continue;
 			}
		goto std;

	}
}

char *
copy(ap)
char *ap;
{
	register char *p, *np;
	char *onp;
	register n;
	int na;

	na = nargs();
	p = ap;
	n = 0;
	if (*p==0)
		return(0);
	do
		n++;
	while (*p++);
	if (na>1) {
		p = (&ap)[1];
		while (*p++)
			n++;
	}
	onp = np = alloc(n);
	p = ap;
	while (*np++ = *p++);
	if (na>1) {
		p = (&ap)[1];
		np--;
		while (*np++ = *p++);
	}
	return(onp);
}

#define	OPHS	560
struct optab *ophash[OPHS];

opsetup()
{
	register struct optab *optp, **ophp;
	register int i,t;

	for(i=NREG+5;--i>=0;) regs[i]=alloc(C2_ASIZE);
	for (optp = optab; optp->opstring[0]; optp++) {
		t=7; i=0; while (--t>=0) i+= i+optp->opstring[t];
		ophp = &ophash[i % OPHS];
		while (*ophp++) {
/*			fprintf(stderr,"\ncollision: %d %s %s",
/*				ophp-1-ophash,optp->opstring,(*(ophp-1))->opstring);
*/
			if (ophp > &ophash[OPHS])
				ophp = ophash;
		}
		*--ophp = optp;
	}
}

struct optab *
oplook()
{
	register struct optab *optp,**ophp;
	register char *p,*p2;
	register int t;
	char tempop[20];
	static struct optab OPNULL={"",0};

	for (p=line, p2=tempop; *p && !isspace(*p); *p2++= *p++); *p2=0; p2=p;
	while (isspace(*p2)) ++p2; curlp=p2;
	t=0; while(--p>=line) t += t+*p; ophp = &ophash[t % OPHS];
	while (optp = *ophp) {
		if (equstr(tempop,optp->opstring)) return(optp);
		if ((++ophp) >= &ophash[OPHS]) ophp = ophash;
	}
	curlp = line;
	return(&OPNULL);
}

refcount()
{
	register struct node *p, *lp;
	struct node *labhash[LABHS];
	register struct node **hp;

	for (hp = labhash; hp < &labhash[LABHS];)
		*hp++ = 0;
	for (p = first.forw; p!=0; p = p->forw)
		if (p->op==LABEL) {
			labhash[p->labno % LABHS] = p;
			p->refc = 0;
		}
	for (p = first.forw; p!=0; p = p->forw) {
		if (p->combop==JBR || p->op==CBR || p->op==JSW || p->op==JMP
		  || p->op==SOBGEQ || p->op==SOBGTR || p->op==AOBLEQ || p->op==AOBLSS
		  || p->op==ACB || (p->op==MOVA && p->labno!=0)) {
			p->ref = 0;
			lp = labhash[p->labno % LABHS];
			if (lp==0 || p->labno!=lp->labno)
			for (lp = first.forw; lp!=0; lp = lp->forw) {
				if (lp->op==LABEL && p->labno==lp->labno)
					break;
			}
			if (lp) {
				hp = nonlab(lp)->back;
				if (hp!=lp) {
					p->labno = hp->labno;
					lp = hp;
				}
				p->ref = lp;
				lp->refc++;
			}
		}
	}
	for (p = first.forw; p!=0; p = p->forw)
		if (p->op==LABEL && p->refc==0
		 && (lp = nonlab(p))->op && lp->op!=JSW)
			decref(p);
}

iterate()
{
	register struct node *p, *rp, *p1;

	nchange = 0;
	for (p = first.forw; p!=0; p = p->forw) {

		if ((p->op==JBR||p->op==CBR||p->op==JSW) && p->ref) {
			rp = nonlab(p->ref);
			if (rp->op==JBR && rp->labno && p->labno!=rp->labno) {
				nbrbr++;
				p->labno = rp->labno;
				decref(p->ref);
				rp->ref->refc++;
				p->ref = rp->ref;
				nchange++;
			}
		}
		/* If a conditional branch is followed by an unconditional
		 * branch to the same location, the conditional can be
		 * eliminated.
		 */
		if (p->op==CBR) {
			p1 = nonlab(p->forw);
			if (p1->combop == JBR) {
				if (p->ref == p1->ref) {
					decref(p->ref);
					delnode(p);
					p = p1->back;
					nbrbr++;
					nchange++;
					continue;
				}
			}
		}
#ifndef COPYCODE
		if (p->op==CBR && (p1 = p->forw)->combop==JBR) {/* combop: RET problems */
#else
		if (p->op==CBR && (p1 = p->forw)->combop==JBR &&
		    p->ref) {/* combop: RET problems */
#endif
			rp = p->ref;
			do
				rp = rp->back;
			while (rp->op==LABEL);
			if (rp==p1) {
				decref(p->ref);
				p->ref = p1->ref;
				p->labno = p1->labno;
#ifdef COPYCODE
				if (p->labno == 0)
					p->code = p1->code;
#endif
				p1->forw->back = p;
				p->forw = p1->forw;
				p->subop = revbr[p->subop];
				p->pop=0;
				nchange++;
				nskip++;
			}
		}

		if (p->op==JBR || p->op==JMP) {
			
			while (p->forw && p->forw->op!=LABEL && p->forw->op!=DLABEL
				&& p->forw->op!=EROU && p->forw->op!=END
				&& p->forw->op!=ALIGN
				&& p->forw->op!=0 && p->forw->op!=DATA) {
				nchange++;
				iaftbr++;
				if (p->forw->ref)
					decref(p->forw->ref);
				p->forw = p->forw->forw;
				p->forw->back = p;
			}
			rp = p->forw;
			while (rp && rp->op==LABEL) {
				if (p->ref == rp) {
					p->back->forw = p->forw;
					p->forw->back = p->back;
					p = p->back;
					decref(rp);
					nchange++;
					njp1++;
					break;
				}
				rp = rp->forw;
			}
			xjump(p);
			p = codemove(p);
		}
	}
}

/* remove_branch_to_return
 *
 * Routine to remove uncontional branches which just branch to a
 * return. They are just replaced with a return.
 */
static void
remove_branch_to_return()
{
	register struct node	
		*ptr,		/* Pointer to current instruction */
		*dest,		/* destination instruction for branch */
		*nextdest;	/* temporary for comparison */
	int count;

	for ( ptr = first.forw; ptr != NULL; ptr = ptr->forw ) {
		if (ptr->combop == JBR || ptr->combop==JMP) {
			
			/* We have an unconditional jump/branch to a
			 * label.  Find the instruction after the
			 * label(s), and if it is a return, convert 
			 * the jump/branch to the appropriate
			 * return and decrease the reference to the
			 * label.
			 */

			/*
			 * Search through a list of unconditional
			 * branches.  These should have been 
			 * eliminated, but just in case.
			 */
			nextdest = ptr;
			dest = nonlab(ptr->ref);
			while ((dest != nextdest)	/* L1:  jmp L1 */
			    && (dest->combop == JBR
			    ||  dest->combop == JMP)) {
				nextdest = dest;
				dest = nonlab(dest->ref);
			}
			if ((dest->combop == T(JBR,RET))
			    || (dest->combop == T(JBR,RSB))
			   ) {
			   	/* The unconditional branch/jump is to a
				 * return, so just change it to a return.
				 */
				ptr->labno = 0;
				ptr->combop = dest->combop;
				ptr->pop = dest->pop;
				decref(ptr->ref);
				ptr->ref = NULL;
				nbrbr++;
			}
		}

	}
}

xjump(p1)
register struct node *p1;
{
	register struct node *p2, *p3;
	int nxj;

	nxj = 0;
	if ((p2 = p1->ref)==0)
		return(0);
	for (;;) {
		while ((p1 = p1->back) && p1->op==LABEL);
		while ((p2 = p2->back) && p2->op==LABEL);
		if (!equop(p1, p2) || p1==p2)
			return(nxj);
		p3 = insertl(p2);
		p1->combop = JBR;
		p1->pop=0;
		p1->ref = p3;
		p1->labno = p3->labno;
		p1->code = 0;
		nxj++;
		nxjump++;
		nchange++;
	}
}

struct node *
insertl(op)
register struct node *op;
{
	register struct node *lp;

	if (op->op == LABEL) {
		op->refc++;
		return(op);
	}
	if (op->back->op == LABEL) {
		op = op->back;
		op->refc++;
		return(op);
	}
	lp = alloc(sizeof first);
	lp->combop = LABEL;
	lp->labno = isn++;
	lp->ref = 0;
	lp->code = 0;
	lp->refc = 1;
	lp->back = op->back;
	lp->forw = op;
	op->back->forw = lp;
	op->back = lp;
	return(lp);
}

struct node *
codemove(ap)
struct node *ap;
{
	register struct node *p1, *p2, *p3;
	struct node *t, *tl;
	int n;

	p1 = ap;
/* last clause to avoid infinite loop on partial compiler droppings:
	L183:	jbr L179
	L191:	jbr L179
			casel r0,$0,$1
	L193:	.word L183-L193
			.word L191-L193
	L179:	ret
*/
	if (p1->op!=JBR || (p2 = p1->ref)==0 || p2==p1->forw)
		return(p1);
	while (p2->op == LABEL)
		if ((p2 = p2->back) == 0)
			return(p1);
	if (p2->op!=JBR && p2->op!=JMP)
		goto ivloop;
	p2 = p2->forw;
	p3 = p1->ref;
	while (p3) {
		if (p3->op==JBR || p3->op==JMP) {
			if (p1==p3)
				return(p1);
			ncmot++;
			nchange++;
			p1->back->forw = p2;
			p1->forw->back = p3;
			p2->back->forw = p3->forw;
			p3->forw->back = p2->back;
			p2->back = p1->back;
			p3->forw = p1->forw;
			decref(p1->ref);
			return(p2);
		} else
			p3 = p3->forw;
	}
	return(p1);
ivloop:
	if (p1->forw->op!=LABEL)
		return(p1);
	p3 = p2 = p2->forw;
	n = 16;
	do {
		if ((p3 = p3->forw) == 0 || p3==p1 || --n==0)
			return(p1);
	} while (p3->op!=CBR || p3->labno!=p1->forw->labno);
	do 
		if ((p1 = p1->back) == 0)
			return(ap);
	while (p1!=p3);
	p1 = ap;
	tl = insertl(p1);
	p3->subop = revbr[p3->subop];
	p3->pop=0;
	decref(p3->ref);
	p2->back->forw = p1;
	p3->forw->back = p1;
	p1->back->forw = p2;
	p1->forw->back = p3;
	t = p1->back;
	p1->back = p2->back;
	p2->back = t;
	t = p1->forw;
	p1->forw = p3->forw;
	p3->forw = t;
	p2 = insertl(p1->forw);
	p3->labno = p2->labno;
#ifdef COPYCODE
	if (p3->labno == 0)
		p3->code = p2->code;
#endif
	p3->ref = p2;
	decref(tl);
	if (tl->refc<=0)
		nrlab--;
	loopiv++;
	nchange++;
	return(p3);
}

comjump()
{
	register struct node *p1, *p2, *p3;

	for (p1 = first.forw; p1!=0; p1 = p1->forw)
		if (p1->op==JBR && ((p2 = p1->ref) && p2->refc > 1
				|| p1->subop==RET || p1->subop==RSB))
			for (p3 = p1->forw; p3!=0; p3 = p3->forw)
				if (p3->op==JBR && p3->ref == p2)
					backjmp(p1, p3);
}

backjmp(ap1, ap2)
struct node *ap1, *ap2;
{
	register struct node *p1, *p2, *p3;

	p1 = ap1;
	p2 = ap2;
	for(;;) {
		while ((p1 = p1->back) && p1->op==LABEL);
		p2 = p2->back;
		if (equop(p1, p2)) {
			p3 = insertl(p1);
			p2->back->forw = p2->forw;
			p2->forw->back = p2->back;
			p2 = p2->forw;
			decref(p2->ref);
			p2->combop = JBR; /* to handle RET */
			p2->pop=0;
			p2->labno = p3->labno;
#ifdef COPYCODE
			p2->code = 0;
#endif
			p2->ref = p3;
			nchange++;
			ncomj++;
		} else
			return;
	}
}