[Soot-list] Constant propagation analysis in SOOT

[Zhoulai FU]

Hi, Bernhard,

Thanks for your quick reply.  My expected results will be a mapping from 'x' to the value lattice 3 and 'unknown', respectively for  

y=3; z=3; if (?) {x=y} else {x=z};
and 
y=2; z=4; if (?) {x=y} else {x=z};

If I understand correctly, the current implementation in SOOT's "soot.jimple.toolkits.scalar.ConstantPropagatorAndFolder" takes only one pass  (thus its algorithm should be  linear), so I think it would be easier to rewrite the analysis than to extend it for a more precise constant propagation.  Let me know pls if I misunderstand. 

 Zhoulai

On Sep 10, 2013, at 7:37 AM, Bernhard Berger <berber at tzi.de> wrote:

> Hi Zhoulai,
> 
> what is the result you want to get? Just the fact that x in print(x) is constant in all cases or that x is definitely 3 (what would be your expected result in the case that y = 2 and z = 4)? Do you want this information intra procedural or inter procedural?
> 
> The ConstantPropagatorAndFolder works in a intra procedural way and propagates nuemric constants and calculates the result of expressions on numeric constants. I think the current implementation can be extended to a version that checks that all definitions of a use have the same constant value. If you change the code feel free to contribute the enhancements back to the soot community.
> 
> Regards,
> 
> Bernhard 
> 
> Am 10.09.2013 um 07:19 schrieb Zhoulai <zell08v at gmail.com>:
> 
>> Dear all,
>> 
>> I am about to use  a constant propagation/folder  analysis under Soot framework. It seems  that there exists  one such implementation in SOOT already:
>> 
>> soot.jimple.toolkits.scalar.ConstantPropagatorAndFolder
>> 
>> However,  this implementation seems to be naive.  If I understand correctly its source code, 
>> 
>> http://www.massapi.com/source/sootsrc-2.4.0/src/soot/jimple/toolkits/scalar/ConstantPropagatorAndFolder.java.html
>> 
>> the implementation associates with local variables a constant only if this  underlined variable has a single definition site.   For example, the implementation  cannot decide that 'x' is a constant  for the snippet below:
>> 
>> y=3; z=3; if (?) {x=y} else {x=z};
>> print (x);
>> 
>> In my application, I need that 'x' be recognized as constant. Although this is not a difficult problem, I would try to avoid code duplication whenever possible. So would you please tell me whether Soot has built in a more sophisticated constant propagation analysis than its "ConstantPropagatorAndFolder" mentioned above, such as the conditional constant propagation?  Thanks in advance. 
>> 
>> Zhoulai (zell)
>> 
>> 
>> 
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