February 20, 2006  CS516 Project 1
Clarifications from Prof Ryder and Weilei Zhang
(this note supercedes earlier notes)

The starting points for the thread-specific unsafe points-to 
analysis are those run() methods for threads in the application 
program. You do NOT trace threads in the Java libraries.

There are several other information and assumptions based on this
clarification:

1) What is considered a thread? the classes inheriting java.lang.Thread 
or implementating java.lang.Runnable. Actually in Java, a class is not 
necessarily a thread if it only implements java.lang.Runnable, but you 
can make this simple assumption for the project.

2) You can assume that each thread run() call can be analyzed
separately, deriving thread-specific points-to sets and call graphs
for threads of that type. 

Just so you know, in mtrt benchmark, there is one thread run() in the
application, but 62 in the library.

3) Each thread run() method needs to be analyzed only once as the
starting point of a thread. It is the run() method, not the callsite
(e.g., t.start() which calls run()) that is the root of the thread
call graph.

4) What if a thread (A) calls another thread(B)?  To simplify things,
in analyzing thread A, B.run() can be regarded in the same way as
other callees. That is, you will consider those methods called as part
of thread B to have been called from thread A, and so as belonging to
the execution of thread A.  However, you also will need to analyze
A.run() and B.run() separately to get an estimate for thread B
independent from thread A.

5) The information from a global points-to analysis is needed because:
i) You need the global call graph to decide which thread run() methods
are to be analyzed (i.e., are reachable in the program from main()
during execution).  ii) You need the global points-to results to
process statements which may refer to the thread receiver object(s) or its
(their) fields. (Note: if there are multiple receiver objects of different
types, treat them all as one abstract thread object in terms of the
points-to's gathered.)  (Global here means whole-program analysis.)
In our project, the global points-to analysis is the existing 0-CFA
analysis with a call graph constructed on-the-fly.