[Soot-list] A question about using a subset of optimizaitons directly on bytecode

[David Beaumont]

Hi,
    I have been playing with soot to do some bytecode optimization but
was wondering how easy it would be to using a few of the optimizations
on bytecode directly, rather than going via the main command line
tool.

Basically I am generating some bytecode and would like to pass _some_
of the methods through a specific set of Jimple optimizations.

Ideally I'd be looking to write a filter that takes in a byte[] of the
method's bytecode and returns the optimized bytecode. I believe that
the optimizations I am looking to perform can be made safe to be
performed on a per-method basis (with reference to other classes via
the soot classpath).

Basically some of the code I am generating will contain bytecode equivalent to:

if (false && someCondition) {
  unreachableCode();
}

or

if (someConstant < biggerConstant) {
  unreachableCode();
}

And I would like to detect and remove the unreachable code sequences.

Basically I think I want to apply:

* jop.cpf - constant propagation
   "false && x"
 -->
   "false"

* jop.cbf - constant branchfolding
   if (false) {
     unreachableCode();
   }
 -->
   goto x;
   unreachableCode();
   x:

* jop.uce1 - unreachable code elimination
   goto x;
   unreachableCode();
   x:
 -->
   goto x;
   x:

* jop.ubf1 - unconditional branch folding
   goto x;
   x:
 -->
   <nothing>

But only to a known subset of methods and a subset of classes (this
has to be as faster as possible).

Many thanks in advance for any help or advice,

  David

-- 
David Beaumont :: Mobile Software Engineer :: Google
Google UK Ltd, Belgrave House, 76 Buckingham Palace Road, London SW1W 9TQ
Tel +44-20-7031-3000 :: Fax +44-20-7031-3001