Ejemplo n.º 1
0
Node*
typebsw(Case *c0, int ncase)
{
	NodeList *cas;
	Node *a, *n;
	Case *c;
	int i, half;
	Val v;

	cas = nil;

	if(ncase < Ncase) {
		for(i=0; i<ncase; i++) {
			n = c0->node;

			switch(c0->type) {

			case Ttypenil:
				v.ctype = CTNIL;
				a = nod(OIF, N, N);
				a->ntest = nod(OEQ, facename, nodlit(v));
				typecheck(&a->ntest, Erv);
				a->nbody = list1(n->right);		// if i==nil { goto l }
				cas = list(cas, a);
				break;

			case Ttypevar:
				a = typeone(n);
				cas = list(cas, a);
				break;

			case Ttypeconst:
				a = nod(OIF, N, N);
				a->ntest = nod(OEQ, hashname, nodintconst(c0->hash));
				typecheck(&a->ntest, Erv);
				a->nbody = list1(typeone(n));
				cas = list(cas, a);
				break;
			}
			c0 = c0->link;
		}
		return liststmt(cas);
	}

	// find the middle and recur
	c = c0;
	half = ncase>>1;
	for(i=1; i<half; i++)
		c = c->link;
	a = nod(OIF, N, N);
	a->ntest = nod(OLE, hashname, nodintconst(c->hash));
	typecheck(&a->ntest, Erv);
	a->nbody = list1(typebsw(c0, half));
	a->nelse = list1(typebsw(c->link, ncase-half));
	return a;
}
Ejemplo n.º 2
0
Archivo: swt.c Proyecto: 8l/go
/*
 * convert switch of the form
 *	switch v := i.(type) { case t1: ..; case t2: ..; }
 * into if statements
 */
static void
typeswitch(Node *sw)
{
	Node *def;
	NodeList *cas, *hash;
	Node *a, *n;
	Case *c, *c0, *c1;
	int ncase;
	Type *t;
	Val v;

	if(sw->ntest == nil)
		return;
	if(sw->ntest->right == nil) {
		setlineno(sw);
		yyerror("type switch must have an assignment");
		return;
	}
	walkexpr(&sw->ntest->right, &sw->ninit);
	if(!istype(sw->ntest->right->type, TINTER)) {
		yyerror("type switch must be on an interface");
		return;
	}
	cas = nil;

	/*
	 * predeclare temporary variables
	 * and the boolean var
	 */
	facename = temp(sw->ntest->right->type);
	a = nod(OAS, facename, sw->ntest->right);
	typecheck(&a, Etop);
	cas = list(cas, a);

	casebody(sw, facename);

	boolname = temp(types[TBOOL]);
	typecheck(&boolname, Erv);

	hashname = temp(types[TUINT32]);
	typecheck(&hashname, Erv);

	t = sw->ntest->right->type;
	if(isnilinter(t))
		a = syslook("efacethash", 1);
	else
		a = syslook("ifacethash", 1);
	argtype(a, t);
	a = nod(OCALL, a, N);
	a->list = list1(facename);
	a = nod(OAS, hashname, a);
	typecheck(&a, Etop);
	cas = list(cas, a);

	c0 = mkcaselist(sw, Stype);
	if(c0 != C && c0->type == Tdefault) {
		def = c0->node->right;
		c0 = c0->link;
	} else {
		def = nod(OBREAK, N, N);
	}
	
	/*
	 * insert if statement into each case block
	 */
	for(c=c0; c!=C; c=c->link) {
		n = c->node;
		switch(c->type) {

		case Ttypenil:
			v.ctype = CTNIL;
			a = nod(OIF, N, N);
			a->ntest = nod(OEQ, facename, nodlit(v));
			typecheck(&a->ntest, Erv);
			a->nbody = list1(n->right);		// if i==nil { goto l }
			n->right = a;
			break;
		
		case Ttypevar:
		case Ttypeconst:
			n->right = typeone(n);
			break;
		}
	}

	/*
	 * generate list of if statements, binary search for constant sequences
	 */
	while(c0 != C) {
		if(c0->type != Ttypeconst) {
			n = c0->node;
			cas = list(cas, n->right);
			c0=c0->link;
			continue;
		}
		
		// identify run of constants
		c1 = c = c0;
		while(c->link!=C && c->link->type==Ttypeconst)
			c = c->link;
		c0 = c->link;
		c->link = nil;

		// sort by hash
		c1 = csort(c1, typecmp);
		
		// for debugging: linear search
		if(0) {
			for(c=c1; c!=C; c=c->link) {
				n = c->node;
				cas = list(cas, n->right);
			}
			continue;
		}

		// combine adjacent cases with the same hash
		ncase = 0;
		for(c=c1; c!=C; c=c->link) {
			ncase++;
			hash = list1(c->node->right);
			while(c->link != C && c->link->hash == c->hash) {
				hash = list(hash, c->link->node->right);
				c->link = c->link->link;
			}
			c->node->right = liststmt(hash);
		}
		
		// binary search among cases to narrow by hash
		cas = list(cas, typebsw(c1, ncase));
	}
	if(nerrors == 0) {
		cas = list(cas, def);
		sw->nbody = concat(cas, sw->nbody);
		sw->list = nil;
		walkstmtlist(sw->nbody);
	}
}