byte multiply

R=r
OCL=18807
CL=18807

src/cmd/6g/cgen.c

@@ -122,7 +122,10 @@ cgen(Node *n, Node *res)
 	case OADD:
 	case OMUL:
 		a = optoas(n->op, nl->type);
-		goto sbop;
+		if(a != AIMULB)
+			goto sbop;
+		cgen_bmul(n->op, nl, nr, res);
+		break;
 
 	// asymmetric binary
 	case OSUB:

src/cmd/6g/gen.c

@@ -1095,6 +1095,35 @@ ret:
 	;
 }
 
+void
+cgen_bmul(int op, Node *nl, Node *nr, Node *res)
+{
+	Node n1, n2;
+	Type *t;
+	int a;
+
+	t = types[TUINT16];
+	if(issigned[nl->type->etype])
+		t = types[TINT16];
+
+	if(nl->ullman >= nr->ullman) {
+		regalloc(&n1, t, nl);
+		cgen(nl, &n1);
+		regalloc(&n2, t, nr);
+		cgen(nr, &n2);
+	} else {
+		regalloc(&n2, t, nr);
+		cgen(nr, &n2);
+		regalloc(&n1, t, nl);
+		cgen(nl, &n1);
+	}
+	a = optoas(op, t);
+	gins(a, &n2, &n1);
+	gmove(&n1, res);
+	regfree(&n1);
+	regfree(&n2);
+}
+
 void
 checklabels(void)
 {

src/cmd/6g/gg.h

@@ -138,6 +138,7 @@ void	cgen_callinter(Node*, Node*, int);
 void	cgen_proc(Node*);
 void	cgen_callret(Node*, Node*);
 void	cgen_div(int, Node*, Node*, Node*);
+void	cgen_bmul(int, Node*, Node*, Node*);
 void	cgen_shift(int, Node*, Node*, Node*);
 void	genpanic(void);
 int	needconvert(Type*, Type*);