[Pl-seminar] Semantics Seminar Schedule

Mitchell Wand wand at ccs.neu.edu
Mon, 8 Apr 2002 11:31:38 -0400 (EDT)

NU Programming Languages Seminar
Wednesday, April 10, 2002
306 Egan  Hall, Northeastern University
    (building 44 on http://www.campusmap.neu.edu/)
**9:30-11:30**  **NOTE NEW MEETING TIME**

Karen Zee will present

Write Barrier Removal by Static Analysis

We present a new static analysis for removing unnecessary write
barriers in programs that use generational garbage collection. To our
knowledge, this is the first analysis for this purpose. Our algorithm
uses an interprocedural, flow-sensitive pointer analysis to locate
assignments that always create a reference from a younger object to an
older object, then transforms the program to eliminate the write
barriers normally associated with such assignments. To enhance the
effectiveness of the technique, we have implemented two
transformations that reorder object allocations.  These
transformations can dramatically increase the number of write barriers
that our algorithm is able to eliminate.

Results from our implemented system show that our technique can
eliminate the majority of the write barriers in most of the programs
in our benchmark set, producing modest performance improvements of up
to 8% of the overall execution time.  Moreover, by dynamically
instrumenting the executable, we are able to show that for all but two
of our nine benchmark programs, our analysis is close to optimal in
the sense that it eliminates the write barriers for almost all
assignments that do not, in the observed execution, create a reference
from an older object to a younger object.


Upcoming presentations:

5/1  Alan Feuer: the Safe C Runtime Analyzer

Most meetings will be 930-1130 in 306 EG.