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Title: Heap Reference Analysis Using Access Graphs. Presentation by Uday P Khedker, Prof of Computer Science & Engineering at IIT Bombay

  • Colloquium Series
When May 19, 2011
from 12:00 PM to 01:00 PM
Where 4.31/4.33
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Despite significant progress in the theory and practice of program analysis, analysing properties of heap data has not reached the same level of maturity as the analysis of static and stack data. The spatial and temporal structure of stack and static data is well understood while that of heap data seems arbitrary and is unbounded. We devise bounded representations which summarize properties of the heap data. This summarization is based on the structure of the program which manipulates the heap. The resulting summary representations are certain kinds of graphs called access graphs. The boundedness of these representations and the monotonicity of the operations to manipulate them make it possible to compute them through data flow analysis.

An important application which benefits from heap reference analysis is garbage collection, where currently liveness is conservatively approximated by reachability from program variables. As a consequence, current garbage collectors leave a lot of garbage uncollected, a fact which has been confirmed by several empirical studies. We propose the first ever end-to-end static analysis to distinguish live objects from reachable objects. We use this information to make dead objects unreachable by modifying the program. This application is interesting because it requires discovering data flow information representing complex semantics. In particular, we formulate the following new and propose solution methods for them. Together, they cover various combinations of directions of analysis (i.e. forward and backward) and confluence of information (i.e. union and intersection).

Our analysis can also be used for plugging memory leaks in C/C++ languages.


Uday P. Khedker, Amitabha Sanyal, and Amey Karkare

Heap Reference Analysis Using Access Graphs.

ACM Transactions on Programming Languages & Systems. 30, 1 (Nov 2007)



Uday Khedker finished BE (E & TCE) from Jabalpur University in 1986, M.Tech. (CS) from Pune University in 1989, and Ph.D. in Computer Science & Engineering from IIT Bombay in 1995. He taught at the Department of Computer Science at Pune University from 1984 to 2001 and since then is with IIT Bombay where currently he is Professor of Computer Science and Engineering.

His areas of interest are Programming Languages and Compilers and he specialises in data flow analysis and its applications to code optimization. He has published papers in leading journals and conferences, has contributed chapters in Compiler Design Handbook and has authored a book titled "Data Flow Analysis: Theory and Practice". He has also worked very closely with the industry. He has established a GCC Resource Center ( at IIT Bombay to improve GCC and disseminate the knowledge of GCC Internals.

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