There is only one file type that uses the .OP extension:
Report created by OpenPAT (Open Performance Analysis Toolkit) tools, a cross-platform program analysis toolkit that helps identify hotspots, bottlenecks, buffer overflows, and other data and control flow information; contains a report of an instrumented program to show an analysis to the user; stores information, depending on the tool it's generated from, such as hotspot, coverage, or control_flow.
The OP file will be named after the tool it created the report on, e.g., the hotspot tool creates the hotspot.op file.
To locate the tools in your OpenPAT folder you downloaded, select "tools," then "core."
NOTE: OpenPAT is no longer available for download.
Updated: September 27, 2016