stmt.c

lcc,一个可变目标c语言编译器的源码

	tail = codelist;
	codelist = head->prev;
	codelist->next = head->prev = NULL;
	if (sw.ncases > 0)
		swgen(&sw);
	branch(lab);
	head->next->prev = codelist;
	codelist->next = head->next;
	codelist = tail;
}
static void caselabel(Swtch swp, long val, int lab) {
	int k;

	if (swp->ncases >= swp->size)
		{
		long   *vals = swp->values;
		Symbol *labs = swp->labels;
		swp->size *= 2;
		swp->values = newarray(swp->size, sizeof *swp->values, FUNC);
		swp->labels = newarray(swp->size, sizeof *swp->labels, FUNC);
		for (k = 0; k < swp->ncases; k++) {
			swp->values[k] = vals[k];
			swp->labels[k] = labs[k];
		}
		}
	k = swp->ncases;
	for ( ; k > 0 && swp->values[k-1] >= val; k--) {
		swp->values[k] = swp->values[k-1];
		swp->labels[k] = swp->labels[k-1];
	}
	if (k < swp->ncases && swp->values[k] == val)
		error("duplicate case label `%d'\n", val);
	swp->values[k] = val;
	swp->labels[k] = findlabel(lab);
	++swp->ncases;
	if (Aflag >= 2 && swp->ncases == 258)
		warning("more than 257 cases in a switch\n");
}
void swgen(Swtch swp) {
	int *buckets, k, n;
	long *v = swp->values;

	buckets = newarray(swp->ncases + 1,
		sizeof *buckets, FUNC);
	for (n = k = 0; k < swp->ncases; k++, n++) {
		buckets[n] = k;
		while (n > 0 && den(n-1, k) >= density)
			n--;
	}
	buckets[n] = swp->ncases;
	swcode(swp, buckets, 0, n - 1);
}
void swcode(Swtch swp, int b[], int lb, int ub) {
	int hilab, lolab, l, u, k = (lb + ub)/2;
	long *v = swp->values;

	if (k > lb && k < ub) {
		lolab = genlabel(1);
		hilab = genlabel(1);
	} else if (k > lb) {
		lolab = genlabel(1);
		hilab = swp->deflab->u.l.label;
	} else if (k < ub) {
		lolab = swp->deflab->u.l.label;
		hilab = genlabel(1);
	} else
		lolab = hilab = swp->deflab->u.l.label;
	l = b[k];
	u = b[k+1] - 1;
	if (u - l + 1 <= 3)
		{
			int i;
			for (i = l; i <= u; i++)
				cmp(EQ, swp->sym, v[i], swp->labels[i]->u.l.label);
			if (k > lb && k < ub)
				cmp(GT, swp->sym, v[u], hilab);
			else if (k > lb)
				cmp(GT, swp->sym, v[u], hilab);
			else if (k < ub)
				cmp(LT, swp->sym, v[l], lolab);
			else
				assert(lolab == hilab),
				branch(lolab);
			walk(NULL, 0, 0);
		}
	else {
		Tree e;
		Type ty = signedint(swp->sym->type);
		Symbol table = genident(STATIC,
			array(voidptype, u - l + 1, 0), GLOBAL);
		(*IR->defsymbol)(table);
		if (!isunsigned(swp->sym->type) || v[l] != 0)
			cmp(LT, swp->sym, v[l], lolab);
		cmp(GT, swp->sym, v[u], hilab);
		e = (*optree['-'])(SUB, cast(idtree(swp->sym), ty), cnsttree(ty, v[l]));
		if (e->type->size < unsignedptr->size)
			e = cast(e, unsignedlong);
		walk(tree(JUMP, voidtype,
			rvalue((*optree['+'])(ADD, pointer(idtree(table)), e)), NULL),
			0, 0);
		code(Switch);
		codelist->u.swtch.table = table;
		codelist->u.swtch.sym = swp->sym;
		codelist->u.swtch.deflab = swp->deflab;
		codelist->u.swtch.size = u - l + 1;
		codelist->u.swtch.values = &v[l];
		codelist->u.swtch.labels = &swp->labels[l];
		if (v[u] - v[l] + 1 >= 10000)
			warning("switch generates a huge table\n");
	}
	if (k > lb) {
		assert(lolab != swp->deflab->u.l.label);
		definelab(lolab);
		swcode(swp, b, lb, k - 1);
	}
	if (k < ub) {
		assert(hilab != swp->deflab->u.l.label);
		definelab(hilab);
		swcode(swp, b, k + 1, ub);
	}
}
static void cmp(int op, Symbol p, long n, int lab) {
	Type ty = signedint(p->type);

	listnodes(eqtree(op,
			cast(idtree(p), ty),
			cnsttree(ty, n)),
		lab, 0);
}
void retcode(Tree p) {
	Type ty;

	if (p == NULL) {
		if (events.returns)
			apply(events.returns, cfunc, NULL);
		return;
	}
	p = pointer(p);
	ty = assign(freturn(cfunc->type), p);
	if (ty == NULL) {
		error("illegal return type; found `%t' expected `%t'\n",
			p->type, freturn(cfunc->type));
		return;
	}
	p = cast(p, ty);
	if (retv)
		{
			if (iscallb(p))
				p = tree(RIGHT, p->type,
					tree(CALL+B, p->type,
						p->kids[0]->kids[0], idtree(retv)),
					rvalue(idtree(retv)));
			else {
				Type ty = retv->type->type;
				assert(isstruct(ty));
				if (ty->u.sym->u.s.cfields) {
					ty->u.sym->u.s.cfields = 0;
					p = asgntree(ASGN, rvalue(idtree(retv)), p);
					ty->u.sym->u.s.cfields = 1;
				} else
					p = asgntree(ASGN, rvalue(idtree(retv)), p);
			}
			walk(p, 0, 0);
			if (events.returns)
				apply(events.returns, cfunc, rvalue(idtree(retv)));
			return;
		}
	if (events.returns)
		{
			Symbol t1 = genident(AUTO, p->type, level);
			addlocal(t1);
			walk(asgn(t1, p), 0, 0);
			apply(events.returns, cfunc, idtree(t1));
			p = idtree(t1);
		}
	if (!isfloat(p->type))
		p = cast(p, promote(p->type));
	if (isptr(p->type))
		{
			Symbol q = localaddr(p);
			if (q && (q->computed || q->generated))
				warning("pointer to a %s is an illegal return value\n",
					q->scope == PARAM ? "parameter" : "local");
			else if (q)
				warning("pointer to %s `%s' is an illegal return value\n",
					q->scope == PARAM ? "parameter" : "local", q->name);
		}
	walk(tree(mkop(RET,p->type), p->type, p, NULL), 0, 0);
}
void definelab(int lab) {
	Code cp;
	Symbol p = findlabel(lab);

	assert(lab);
	walk(NULL, 0, 0);
	code(Label)->u.forest = newnode(LABEL+V, NULL, NULL, p);
	for (cp = codelist->prev; cp->kind <= Label; )
		cp = cp->prev;
	while (   cp->kind == Jump
	       && cp->u.forest->kids[0]
	       && specific(cp->u.forest->kids[0]->op) == ADDRG+P
	       && cp->u.forest->kids[0]->syms[0] == p) {
		assert(cp->u.forest->kids[0]->syms[0]->u.l.label == lab);
		p->ref--;
		assert(cp->next);
		assert(cp->prev);
		cp->prev->next = cp->next;
		cp->next->prev = cp->prev;
		cp = cp->prev;
		while (cp->kind <= Label)
			cp = cp->prev;
	}
}
Node jump(int lab) {
	Symbol p = findlabel(lab);

	p->ref++;
	return newnode(JUMP+V, newnode(ADDRG+ttob(voidptype), NULL, NULL, p),
		NULL, NULL);
}
void branch(int lab) {
	Code cp;
	Symbol p = findlabel(lab);

	assert(lab);
	walk(NULL, 0, 0);
	code(Label)->u.forest = jump(lab);
	for (cp = codelist->prev; cp->kind < Label; )
		cp = cp->prev;
	while (   cp->kind == Label
	       && cp->u.forest->op == LABEL+V
	       && !equal(cp->u.forest->syms[0], p)) {
		equatelab(cp->u.forest->syms[0], p);
		assert(cp->next);
		assert(cp->prev);
		cp->prev->next = cp->next;
		cp->next->prev = cp->prev;
		cp = cp->prev;
		while (cp->kind < Label)
			cp = cp->prev;
	}
	if (cp->kind == Jump || cp->kind == Switch) {
		p->ref--;
		codelist->prev->next = NULL;
		codelist = codelist->prev;
	} else {
		codelist->kind = Jump;
		if (cp->kind == Label
		&&  cp->u.forest->op == LABEL+V
		&&  equal(cp->u.forest->syms[0], p))
			warning("source code specifies an infinite loop\n");
	}
}
void equatelab(Symbol old, Symbol new) {
	assert(old->u.l.equatedto == NULL);
	old->u.l.equatedto = new;
	new->ref++;
}
static int equal(Symbol lprime, Symbol dst) {
	assert(dst && lprime);
	for ( ; dst; dst = dst->u.l.equatedto)
		if (lprime == dst)
			return 1;
	return 0;
}
/* dostmt - do statement while ( expression ) */
static void dostmt(int lab, Swtch swp, int lev) {
	refinc *= 10.0;
	t = gettok();
	definelab(lab);
	statement(lab, swp, lev);
	definelab(lab + 1);
	expect(WHILE);
	expect('(');
	definept(NULL);
	walk(conditional(')'), lab, 0);
	if (findlabel(lab + 2)->ref)
		definelab(lab + 2);
}

/* foldcond - check if initial test in for(e1;e2;e3) S is necessary */
static int foldcond(Tree e1, Tree e2) {
	int op = generic(e2->op);
	Symbol v;

	if (e1 == 0 || e2 == 0)
		return 0;
	if (generic(e1->op) == ASGN && isaddrop(e1->kids[0]->op)
	&& generic(e1->kids[1]->op) == CNST) {
		v = e1->kids[0]->u.sym;
		e1 = e1->kids[1];
	} else
		return 0;
	if ((op==LE || op==LT || op==EQ || op==NE || op==GT || op==GE)
	&& generic(e2->kids[0]->op) == INDIR
	&& e2->kids[0]->kids[0]->u.sym == v
	&& e2->kids[1]->op == e1->op) {
		e1 = simplify(op, e2->type, e1, e2->kids[1]);
		if (e1->op == CNST+I)
			return e1->u.v.i;
	}
	return 0;
}

/* localaddr - returns q if p yields the address of local/parameter q; otherwise returns 0 */
static Symbol localaddr(Tree p) {
	if (p == NULL)
		return NULL;
	switch (generic(p->op)) {
	case INDIR: case CALL: case ARG:
		return NULL;
	case ADDRL: case ADDRF:
		return p->u.sym;
	case RIGHT: case ASGN:
		if (p->kids[1])
			return localaddr(p->kids[1]);
		return localaddr(p->kids[0]);
	case COND: {
		Symbol q;
		assert(p->kids[1] && p->kids[1]->op == RIGHT);
		if ((q = localaddr(p->kids[1]->kids[0])) != NULL)
			return q;
		return localaddr(p->kids[1]->kids[1]);
		}
	default: {
		Symbol q;
		if (p->kids[0] && (q = localaddr(p->kids[0])) != NULL)
			return q;
		return localaddr(p->kids[1]);
		}
	}
}

/* whilestmt - while ( expression ) statement */
static void whilestmt(int lab, Swtch swp, int lev) {
	Coordinate pt;
	Tree e;

	refinc *= 10.0;
	t = gettok();
	expect('(');
	walk(NULL, 0, 0);
	pt = src;
	e = texpr(conditional, ')', FUNC);
	branch(lab + 1);
	definelab(lab);
	statement(lab, swp, lev);
	definelab(lab + 1);
	definept(&pt);
	walk(e, lab, 0);
	if (findlabel(lab + 2)->ref)
		definelab(lab + 2);
}