The report's XML, and information about the stored procedures used by the report, can be accessed in the front end of CRM using page designer.

1) Go to the report page and open page designer.
2) In the report section, click View XML
3) Objects in the report beginning with "USP" are out of box stored procedures used by the report. 

The screenshot below shows the list of stored procedures referenced in the VSE Survey College Report XML

Screenshot of the VSE Survey College Report XML