add_comparison
add_comparison(expr->left, '>', r_right);
add_comparison(expr->left, SPECIAL_GTE, r_right);
add_comparison(expr->left, '>', r_left);
add_comparison(expr->left, SPECIAL_GTE, r_left);
add_comparison(expr->left, '>', r_left);
add_comparison(expr->left, SPECIAL_GTE, r_left);
add_comparison(expr->left, '<', r_left);
add_comparison(expr->left, SPECIAL_EQUAL, expr->right);
add_comparison(call, comparison, arg);
static void add_comparison(struct expression *left, int comparison, struct expression *right);
add_comparison(expr->unop, op, parent->right);