[LLVMdev] The use-define chain in LLVM

[Jianfei Hu]

Yes, this demanding comes from our recent research project.
If it's avaiable, could you send me the source code of taint-tracking analysis ?
I really appreciate your help. Thanks!

2012/8/9 John Criswell <criswell at illinois.edu>:
> On 8/9/12 12:40 AM, Jianfei Hu wrote:
>>
>> Maybe My statement is not clear. Take an example:
>> main.c:
>> int global;
>> void fun(int array[], int i){
>>         array[i] = i + 1;
>>          global = i;
>> }
>>
>> int main(){
>>         int arr[40], i = 0;
>>         fun(arr, 10);
>>         return 0;
>> }
>> Can I determine whether the value of arr array and global variable
>> have changed after the function call, fun(arr, 10), by LLVM API? It
>> could be more complicated considerring the nested function call, and
>> variable pointer alias. Does LLVM offer the interface to solve that?
>
>
> If you need to compute use-def chains for values that are not in SSA form
> (basically anything that is accessed via LLVM load and store instructions),
> then you'll need to implement your own data-flow analysis to compute the
> reaching definitions using some memory-based abstraction.
>
> There is a points-to analysis for LLVM called DSA within the poolalloc
> project.  It creates a graph of nodes (called DSNodes) which represent
> abstract memory locations.  You could use that to implement a use/def
> analysis that works on global variables, stack objects, and heap objects.
>
> You can get poolalloc using the command svn co
> http://llvm.org/svn/llvm-project/poolalloc/trunk poolalloc
>
> As an FYI, one of our collaborators recently gave us permission to give
> someone the source code for a taint-tracking analysis which is similar to
> reaching definitions analysis.  If you want, I can ask if we can give you a
> copy of it, too.  I assume it's for a research project, correct?
>
> -- John T.
>
>
>>
>> 2012/8/9 Alex Rønne Petersen <xtzgzorex at gmail.com>:
>>>
>>> On Thu, Aug 9, 2012 at 6:57 AM, Jianfei Hu <hujianfei258 at gmail.com>
>>> wrote:
>>>>
>>>> Thanks for your response!
>>>>
>>>> But I want to determine wheter the specific variable's value has been
>>>> changed between
>>>> two usages of variable, and wheter the parameter's value is changed in
>>>> a function. Like the
>>>> reaching definition analysis, and ud chains.
>>>>
>>>>
>>>> 2012/8/9 陳韋任 (Wei-Ren Chen) <chenwj at iis.sinica.edu.tw>:
>>>>>
>>>>> On Thu, Aug 09, 2012 at 11:16:15AM +0800, Jianfei Hu wrote:
>>>>>>
>>>>>> Hello All,
>>>>>>
>>>>>>          Is the use-define chain related API avaliable in LLVM? I want
>>>>>> to get the information
>>>>>> about the variables' value changes at different points in the program.
>>>>>
>>>>>    Is this [1] fit your need?
>>>>>
>>>>> HTH,
>>>>> chenwj
>>>>>
>>>>> [1] http://llvm.org/docs/ProgrammersManual.html#iterate_chains
>>>>
>>>> This just supplys the variables used by the one instruction.
>>>> Is there any other class/API that can meet my demands?
>>>> Or I have to implement it by myself from the llvm IR code?
>>>>
>>>>> --
>>>>> Wei-Ren Chen (陳韋任)
>>>>> Computer Systems Lab, Institute of Information Science,
>>>>> Academia Sinica, Taiwan (R.O.C.)
>>>>> Tel:886-2-2788-3799 #1667
>>>>> Homepage: http://people.cs.nctu.edu.tw/~chenwj
>>>>
>>>>
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>>
>>> I don't know how low-level you plan to work at, but at the LLVM IR
>>
>> Do you mean the LLVM could generate a higher level representative,
>> instead of IR, like AST? I just know the IR code level.
>>
>>> level, a register can only be defined once (LLVM IR is in SSA form),
>>> so while a register can have multiple uses, it can only have one
>>> definition (or none, in the case of registers that aren't
>>> initialized).
>>>
>>> Regards,
>>> Alex
>>
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>
>