PL Seminar talk on Thursday

[Raghavan Komondoor <raghavan@xxxxxxxxxxx>]

I am sorry for mailing out this announcement, but I am doing it
because I did not act quickly enough to get the announcement included
in the weekly talks listing.

Raghavan.

Title of talk:  Semantics-Preserving Procedure Extraction
When and where: 4pm, Thursday (12/9), Room 2310
Speaker:        Raghavan Komondoor
Abstract:

    Procedure extraction is an important program transformation that can
    be used to make programs easier to understand and maintain, to
    facilitate code reuse, and to convert "monolithic" code to modular or
    object-oriented code.  Procedure extraction involves the following
    steps:

      1. The statements to be extracted are identified (by the programmer
         or by a programming tool).
      2. If the statements are not contiguous, they are moved together so
         that they form a sequence that can be extracted into a procedure,
         and so that the semantics of the original code is preserved.
      3. The statements are extracted into a new procedure, and are replaced
         with an appropriate call.
    
    In our work we address step 2: in particular, the conditions under
    which it is possible to move a set of selected statements together
    so that they become "extractable", while preserving semantics.
    Since semantic equivalence is, in general, undecidable, we
    identify sufficient conditions based on control and data
    dependences, and define an algorithm that moves the selected
    statements together when the conditions hold.  We have been able
    to device a proof that our algorithm is semantics-preserving.
    
    While there has been considerable previous work on procedure
    extraction, we believe ours is the first algorithm for
    semantics-preserving procedure extraction given an arbitrary set
    of selected statements in an arbitrary control-flow graph.