1. Download code igniter.
2. Make two copies.
3. Rename the one of the folders as codebase.
4. Create a new eclipse project with existing files as codebase.
5. Copy the below code :

/**
  * @var CI_Config
  */
 var $config;
 /**
  * @var CI_DB_active_record
  */
 var $db;
 /**
  * @var CI_Email
  */
 var $email;
 /**
  * @var CI_Form_validation
  */
 var $form_validation;
 /**
  * @var CI_Input
  */
 var $input;
 /**
  * @var CI_Loader
  */
 var $load;
 /**
  * @var CI_Router
  */
 var $router;
 /**
  * @var CI_Session
  */
 var $session;
 /**
  * @var CI_Table
  */
 var $table;
 /**
  * @var CI_Unit_test
  */
 var $unit;
 /**
  * @var CI_URI
  */
 var $uri;
 /**
  * @var CI_Pagination
  */
 var $pagination;
6. Paste it in these files in the codebase project.

• /system/core/controller.php
• /system/core/model.php

7. You need to paste it right after the class names. e.g.
class CI_Controller {
class CI_Model {
8. Now goto the second project and include the codebase project in the include path.
9. code complete should work now.
For posterity, I wanted to save this on my blog. Basically this is the link I got this from: http://taggedzi.com/articles/display/autocomplete-eclipse-codeigniter-2