expr_eliminate_dups
l = expr_eliminate_dups(e->left.expr);
r = expr_eliminate_dups(e->right.expr);
struct expr *expr_eliminate_dups(struct expr *e);
basedep = expr_eliminate_dups(basedep);
dep = expr_eliminate_dups(dep);
basedep = expr_eliminate_dups(expr_transform(basedep));
dep = expr_eliminate_dups(expr_transform(dep));