[Soot-list] How to determine whether there exists a use for a variable definition later on in the cfg

[John Dean]

Thanks, Cheng!

 

Anyone (including Cheng, of course),

If I use SimpleLocalUses.getUsesOf(unit), according to the api, it retrieves
a list of units that use the definition in the unit arg, but I need to know
where the retrieved units come from (specifically, I need to know if any of
them come from outside the loop that contains the variable's definition). I
know the blocks and statements that are inside the loop, but I don't know
how to tell whether the units retrieved from SimpleLocalUses.getUsesOf(unit)
are in the loop's blocks or in outside blocks.

 

Suggestions?

 

Thanks,

John

 

From: Cheng Zhang [mailto:cheng.zhang.stap at gmail.com] 
Sent: Friday, July 27, 2012 10:38 AM
To: john.dean at park.edu
Cc: soot-list at sable.mcgill.ca
Subject: Re: [Soot-list] How to determine whether there exists a use for a
variable definition later on in the cfg

 

Hi John,

 

You may use the existing classes, like SimpleLocalDefs or SmartLocalDefs, to
do your work.

 

Best,

Cheng 

 

On Fri, Jul 27, 2012 at 11:16 PM, John Dean <jdean4 at kc.rr.com> wrote:

Hi all,

For a given instruction's definition within a loop, I need to determine
whether there exists a use for that definition outside of the loop. By
"definition," I mean a variable is assigned a value. By "use," I mean the
variable is accessed at some later point in the flow of the method's CFG.
I've already been able to gather the instructions in a loop, so I don't need
help with that.

I've looked through the soot api, and the only strategy I can come up with
is to find all the instructions in the cfg that might follow the variable
definition's instruction (while ignoring the instructions in the loop, of
course). And to do that, I would call cfg.getSuccsOf(unit) recursively and
avoid infinite recursive loops by storing all the found instructions in a
list and only adding new instructions if they're not in the list already.

That seems like a lot of work on my part, and I don't want to reinvent the
wheel if there's a better way. Any suggestions?

Thanks,
john

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