[llvm-dev] data flow graph

[John Criswell via llvm-dev]

On 6/18/16 1:38 PM, huyite wrote:
>
> Dear professor John Criswell
>
>       I would like *to implement a new instruction scheduling 
> algorithm* so that I need the Data flow graph(DFG) is input of the 
> algorithm.
>

If I understand correctly, you need the data flow graph of the machine 
instructions, correct?  That would imply that you're analyzing the 
MachineInstr IR and that you need the data dependencies between machine 
instructions, correct?

I do not know of a data flow graph analysis at the MI level. However, we 
have built a very basic reaching definitions analysis for registers at 
the MI level for x86 (it might work on other architectures, too, though 
I'm not sure).  We will be extending it to handle stack locations in the 
near future.  If this could would help you, please let me know.

Have you looked at LLVM's existing instruction scheduler to see how it 
handles data dependencies?

Regards,

John Criswell

> Thanks
>
>    Huy
>
> *From:*John Criswell [mailto:jtcriswel at gmail.com]
> *Sent:* Sunday, June 19, 2016 1:25 AM
> *To:* huyite; llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] data flow graph
>
> Dear Huyite,
>
> Your question, as stated, is too broad to answer.  It would help if 
> your question were more specific; what is it that you want to 
> accomplish?  Are you interested in data flow within SSA virtual 
> registers, or are you interested in data that is stored in memory 
> (which is not in SSA form)?  Are you analyzing code at the LLVM IR 
> level or at the MachineInstr (MI) or MC level?  Are you wanting to 
> print a data-flow graph, or are you developing an analysis that needs 
> to understand a program's data flow in some way?
>
> Without a more specific question, I cannot give a useful answer.
>
> Regards,
>
> John Criswell
>
>
> On 6/16/16 9:15 AM, huyite via llvm-dev wrote:
>
>     Dear all,
>
>           Please help me to generate DFG(Data flow graph) in LLVM.
>
>     Best regards,
>
>         Huy
>
>     //
>
>     /Mobile: +84942976091/
>
>
>
>
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>
> -- 
> John Criswell
> Assistant Professor
> Department of Computer Science, University of Rochester
> http://www.cs.rochester.edu/u/criswell


-- 
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell

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