c12.c

unix v7是最后一个广泛发布的研究型UNIX版本

}

/*
 * Deal with assignments to partial-word fields.
 * The game is that select(x) =+ y turns into
 * select(x =+ select(y)) where the shifts and masks
 * are chosen properly.  The outer select
 * is discarded where the value doesn't matter.
 * Sadly, overflow is undetected on =+ and the like.
 * Pure assignment is handled specially.
 */

lvfield(at)
struct tnode *at;
{
	register struct tnode *t, *t1;
	register struct fasgn *t2;

	t = at;
	switch (t->op) {

	case ASSIGN:
		t2 = getblk(sizeof(*t2));
		t2->op = FSELA;
		t2->type = UNSIGN;
		t1 = t->tr1->tr2;
		t2->mask = ((1<<t1->tr1->value)-1)<<t1->tr2->value;
		t2->tr1 = t->tr1;
		t2->tr2 = t->tr2;
		t = t2;

	case ASANDN:
	case ASPLUS:
	case ASMINUS:
	case ASOR:
	case ASXOR:
	case INCBEF:
	case INCAFT:
	case DECBEF:
	case DECAFT:
		t1 = t->tr1;
		t1->op = FSELR;
		t->tr1 = t1->tr1;
		t1->tr1 = t->tr2;
		t->tr2 = t1;
		t1 = t1->tr2;
		t1 = tnode(COMMA, INT, tconst(t1->tr1->value, INT),
			tconst(t1->tr2->value, INT));
		return(optim(tnode(FSELT, UNSIGN, t, t1)));

	}
	error("Unimplemented field operator");
	return(t);
}

#define	LSTSIZ	20
struct acl {
	int nextl;
	int nextn;
	struct tnode *nlist[LSTSIZ];
	struct tnode *llist[LSTSIZ+1];
};

acommute(atree)
{
	struct acl acl;
	int d, i, op, flt, d1;
	register struct tnode *t1, **t2, *tree;
	struct tnode *t;

	acl.nextl = 0;
	acl.nextn = 0;
	tree = atree;
	op = tree->op;
	flt = isfloat(tree);
	insert(op, tree, &acl);
	acl.nextl--;
	t2 = &acl.llist[acl.nextl];
	if (!flt) {
		/* put constants together */
		for (i=acl.nextl; i>0; i--) {
			if (t2[0]->op==CON && t2[-1]->op==CON) {
				acl.nextl--;
				t2--;
				const(op, &t2[0]->value, t2[1]->value);
			} else if (t = lconst(op, t2[-1], t2[0])) {
				acl.nextl--;
				t2--;
				t2[0] = t;
			}
		}
	}
	if (op==PLUS || op==OR) {
		/* toss out "+0" */
		if (acl.nextl>0 && (t1 = isconstant(*t2)) && t1->value==0
		 || (*t2)->op==LCON && (*t2)->lvalue==0) {
			acl.nextl--;
			t2--;
		}
		if (acl.nextl <= 0) {
			if ((*t2)->type==CHAR)
				*t2 = tnode(LOAD, tree->type, *t2, NULL);
			(*t2)->type = tree->type;
			return(*t2);
		}
		/* subsume constant in "&x+c" */
		if (op==PLUS && t2[0]->op==CON && t2[-1]->op==AMPER) {
			t2--;
			t2[0]->tr1->offset =+ t2[1]->value;
			acl.nextl--;
		}
	} else if (op==TIMES || op==AND) {
		t1 = acl.llist[acl.nextl];
		if (t1->op==CON) {
			if (t1->value==0)
				return(t1);
			if (op==TIMES && t1->value==1 && acl.nextl>0)
				if (--acl.nextl <= 0) {
					t1 = acl.llist[0];
					if (tree->type == UNSIGN)
						t1->type = tree->type;
					return(t1);
				}
		}
	}
	if (op==PLUS && !flt)
		distrib(&acl);
	tree = *(t2 = &acl.llist[0]);
	d = max(degree(tree), islong(tree->type));
	if (op==TIMES && !flt)
		d++;
	for (i=0; i<acl.nextl; i++) {
		t1 = acl.nlist[i];
		t1->tr2 = t = *++t2;
		d1 = degree(t);
		/*
		 * PDP-11 strangeness:
		 * rt. op of ^ must be in a register.
		 */
		if (op==EXOR && dcalc(t, 0)<=12) {
			t1->tr2 = t = optim(tnode(LOAD, t->type, t));
			d1 = t->degree;
		}
		t1->degree = d = d==d1? d+islong(t1->type): max(d, d1);
		t1->tr1 = tree;
		tree = t1;
		if (tree->type==LONG) {
			if (tree->op==TIMES)
				tree = hardlongs(tree);
			else if (tree->op==PLUS && (t = isconstant(tree->tr1))
			       && t->value < 0 && t->type!=UNSIGN) {
				tree->op = MINUS;
				t->value = - t->value;
				t = tree->tr1;
				tree->tr1 = tree->tr2;
				tree->tr2 = t;
			}
		}
	}
	if (tree->op==TIMES && ispow2(tree))
		tree->degree = max(degree(tree->tr1), islong(tree->type));
	return(tree);
}

distrib(list)
struct acl *list;
{
/*
 * Find a list member of the form c1c2*x such
 * that c1c2 divides no other such constant, is divided by
 * at least one other (say in the form c1*y), and which has
 * fewest divisors. Reduce this pair to c1*(y+c2*x)
 * and iterate until no reductions occur.
 */
	register struct tnode **p1, **p2;
	struct tnode *t;
	int ndmaj, ndmin;
	struct tnode **dividend, **divisor;
	struct tnode **maxnod, **mindiv;

    loop:
	maxnod = &list->llist[list->nextl];
	ndmaj = 1000;
	dividend = 0;
	for (p1 = list->llist; p1 <= maxnod; p1++) {
		if ((*p1)->op!=TIMES || (*p1)->tr2->op!=CON)
			continue;
		ndmin = 0;
		for (p2 = list->llist; p2 <= maxnod; p2++) {
			if (p1==p2 || (*p2)->op!=TIMES || (*p2)->tr2->op!=CON)
				continue;
			if ((*p1)->tr2->value == (*p2)->tr2->value) {
				(*p2)->tr2 = (*p1)->tr1;
				(*p2)->op = PLUS;
				(*p1)->tr1 = (*p2);
				*p1 = optim(*p1);
				squash(p2, maxnod);
				list->nextl--;
				goto loop;
			}
			if (((*p2)->tr2->value % (*p1)->tr2->value) == 0)
				goto contmaj;
			if (((*p1)->tr2->value % (*p2)->tr2->value) == 0) {
				ndmin++;
				mindiv = p2;
			}
		}
		if (ndmin > 0 && ndmin < ndmaj) {
			ndmaj = ndmin;
			dividend = p1;
			divisor = mindiv;
		}
    contmaj:;
	}
	if (dividend==0)
		return;
	t = list->nlist[--list->nextn];
	p1 = dividend;
	p2 = divisor;
	t->op = PLUS;
	t->type = (*p1)->type;
	t->tr1 = (*p1);
	t->tr2 = (*p2)->tr1;
	(*p1)->tr2->value =/ (*p2)->tr2->value;
	(*p2)->tr1 = t;
	t = optim(*p2);
	if (p1 < p2) {
		*p1 = t;
		squash(p2, maxnod);
	} else {
		*p2 = t;
		squash(p1, maxnod);
	}
	list->nextl--;
	goto loop;
}

squash(p, maxp)
struct tnode **p, **maxp;
{
	register struct tnode **np;

	for (np = p; np < maxp; np++)
		*np = *(np+1);
}

const(op, vp, av)
int *vp;
{
	register int v;
	struct { unsigned u;};

	v = av;
	switch (op) {

	case PTOI:
		(*vp).u =/ v;
		return;

	case PLUS:
		*vp =+ v;
		return;

	case TIMES:
		*vp =* v;
		return;

	case AND:
		*vp =& v;
		return;

	case OR:
		*vp =| v;
		return;

	case EXOR:
		*vp =^ v;
		return;

	case DIVIDE:
	case MOD:
		if (v==0)
			error("Divide check");
		else
			if (op==DIVIDE)
				*vp =/ v;
			else
				*vp =% v;
		return;

	case RSHIFT:
		*vp =>> v;
		return;

	case LSHIFT:
		*vp =<< v;
		return;

	case ANDN:
		*vp =& ~ v;
		return;
	}
	error("C error: const");
}

struct tnode *
lconst(op, lp, rp)
register struct tnode *lp, *rp;
{
	long l, r;

	if (lp->op==LCON)
		l = lp->lvalue;
	else if (lp->op==ITOL && lp->tr1->op==CON) {
		if (lp->tr1->type==INT)
			l = lp->tr1->value;
		else
			l = (unsigned)lp->tr1->value;
	} else
		return(0);
	if (rp->op==LCON)
		r = rp->lvalue;
	else if (rp->op==ITOL && rp->tr1->op==CON) {
		if (rp->tr1->type==INT)
			r = rp->tr1->value;
		else
			r = (unsigned)rp->tr1->value;
	} else
		return(0);
	switch (op) {

	case PLUS:
		l += r;
		break;

	case MINUS:
		l -= r;
		break;

	case TIMES:
	case LTIMES:
		l *= r;
		break;

	case DIVIDE:
	case LDIV:
		if (r==0)
			error("Divide check");
		else
			l /= r;
		break;

	case MOD:
	case LMOD:
		if (r==0)
			error("Divide check");
		else
			l %= r;
		break;

	case AND:
		l &= r;
		break;

	case ANDN:
		l &= ~r;
		break;

	case OR:
		l |= r;
		break;

	case EXOR:
		l ^= r;
		break;

	case LSHIFT:
		l <<= r;
		break;

	case RSHIFT:
		l >>= r;
		break;

	default:
		return(0);
	}
	if (lp->op==LCON) {
		lp->lvalue = l;
		return(lp);
	}
	lp = getblk(sizeof(struct lconst));
	lp->op = LCON;
	lp->type = LONG;
	lp->lvalue = l;
	return(lp);
}

insert(op, atree, alist)
struct acl *alist;
{
	register d;
	register struct acl *list;
	register struct tnode *tree;
	int d1, i;
	struct tnode *t;

	tree = atree;
	list = alist;
ins:
	if (tree->op != op)
		tree = optim(tree);
	if (tree->op == op && list->nextn < LSTSIZ-2) {
		list->nlist[list->nextn++] = tree;
		insert(op, tree->tr1, list);
		insert(op, tree->tr2, list);
		return;
	}
	if (!isfloat(tree)) {
		/* c1*(x+c2) -> c1*x+c1*c2 */
		if ((tree->op==TIMES||tree->op==LSHIFT)
		  && tree->tr2->op==CON && tree->tr2->value>0
		  && tree->tr1->op==PLUS && tree->tr1->tr2->op==CON) {
			d = tree->tr2->value;
			if (tree->op==TIMES)
				tree->tr2->value =* tree->tr1->tr2->value;
			else
				tree->tr2->value = tree->tr1->tr2->value << d;
			tree->tr1->tr2->value = d;
			tree->tr1->op = tree->op;
			tree->op = PLUS;
			tree = optim(tree);
			if (op==PLUS)
				goto ins;
		}
	}
	d = degree(tree);
	for (i=0; i<list->nextl; i++) {
		if ((d1=degree(list->llist[i]))<d) {
			t = list->llist[i];
			list->llist[i] = tree;
			tree = t;
			d = d1;
		}
	}
	list->llist[list->nextl++] = tree;
}

tnode(op, type, tr1, tr2)
struct tnode *tr1, *tr2;
{
	register struct tnode *p;

	p = getblk(sizeof(*p));
	p->op = op;
	p->type = type;
	p->degree = 0;
	p->tr1 = tr1;
	if (opdope[op]&BINARY)
		p->tr2 = tr2;
	else
		p->tr2 = NULL;
	return(p);
}

tconst(val, type)
{
	register struct tconst *p;

	p = getblk(sizeof(*p));
	p->op = CON;
	p->type = type;
	p->value = val;
	return(p);
}

getblk(size)
{
	register *p;

	if (size&01)
		abort();
	p = curbase;
	if ((curbase =+ size) >= coremax) {
		if (sbrk(1024) == -1) {
			error("Out of space-- c1");
			exit(1);
		}
		coremax =+ 1024;
	}
	return(p);
}

islong(t)
{
	if (t==LONG)
		return(2);
	return(1);
}

isconstant(at)
struct tnode *at;
{
	register struct tnode *t;

	t = at;
	if (t->op==CON || t->op==SFCON)
		return(t);
	if (t->op==ITOL && t->tr1->op==CON)
		return(t->tr1);
	return(0);
}

hardlongs(at)
struct tnode *at;
{
	register struct tnode *t;

	t = at;
	switch(t->op) {

	case TIMES:
	case DIVIDE:
	case MOD:
		t->op =+ LTIMES-TIMES;
		break;

	case ASTIMES:
	case ASDIV:
	case ASMOD:
		t->op =+ LASTIMES-ASTIMES;
		t->tr1 = tnode(AMPER, LONG+PTR, t->tr1);
		break;

	default:
		return(t);
	}
	return(optim(t));
}