1. Checkpoint Presentation Vas Chellappa Matt Moore
Data Access Profiling and Improved Structure Field Regrouping in Pegasus
Checkpoint Presentation
Vas Chellappa
Matt Moore

2. Introduction Based on the work of Chilimbi et al Objectives:
Trishul M. Chilimbi, Bob Davidson, and James R. Larus. ``Cache-Conscious Structure Definition,'' in Proceedings of the ACM SIGPLAN '99 Conference on Programming Language Design and Implementation, pages 13-24, May 1999.
Objectives:
Recommending improved structure field ordering for cache performance
Improve upon the naïve greedy algorithm for reordering that Chilimbi et al used
Implement this in the new Pegasus Simulator
Optimizing Compilers for Modern Architectures / SP05 / Matt Moore, Vas Chellappa

3. Approach Pegasus Implementation Regrouping Algorithm
Data Access Profiling to track contemporaneous field accesses to build the Field Affinity Graphs
Modify Simulator interface to SimpleScalar (3rd party cache simulator) to achieve this
Regrouping Algorithm
Field Affinity Graphs built by the modified Simulator are then used to recommend reorderings based on a new regrouping algorithm
Talk about what the Field Affinity Graph is
Optimizing Compilers for Modern Architectures / SP05 / Matt Moore, Vas Chellappa

4. Checkpoint Objectives
Goal 1: Pegasus Implementation
Design of Profiling System Complete
Implementation of Design Significant Progress
Goal 2: Regrouping Algorithm
Determination of NP-Hardness Complete
Implementation of Optimal or Heuristic regrouping algorithm Complete
Optimizing Compilers for Modern Architectures / SP05 / Matt Moore, Vas Chellappa

5. Checkpoint Progress Goal 1
Pegasus Implementation
Modifying simulator to propagate struct and field information on wires to SimpleScalar
Modified code that interfaces with SimpleScalar to track contemporaneity of field accesses
Field Affinity Graphs are built based on this information
Optimizing Compilers for Modern Architectures / SP05 / Matt Moore, Vas Chellappa

6. Checkpoint Progress Goal 2
Regrouping Algorithm
Unfortunately found to be NP-Hard (based on k-coloring reduction)
Uses modified simulator’s output
Implemented a heuristic based on Weighted Matchings in the Field Affinity Graphs
Optimizing Compilers for Modern Architectures / SP05 / Matt Moore, Vas Chellappa

7. What’s Next… Finish up the simulator modifications
Tie together the implementations
Test/Debug
Test performance improvement of recommended over original ordering
Optimizing Compilers for Modern Architectures / SP05 / Matt Moore, Vas Chellappa