bh_inc
| GVAR '=' OP1 '(' expr ')' { $$ = bh_inc($1, $5, NULL); }
| GVAR '=' OP4 '(' expr ',' vargs ')' { $$ = bh_inc($1, $5, $7); }
struct bt_stmt *bh_inc(const char *, struct bt_arg *, struct bt_arg *);