[llvm-dev] Find loops in LLVM bytecode

[John Criswell via llvm-dev]

On 9/22/15 8:22 PM, Jia-Ju Bai via llvm-dev wrote:
> Hi,
> I want to find simple loops in LLVM bytecode, and extract the basic 
> information of the loop.
>
> For example:
>     for (i=0; i<1000; i++)
>         sum += i;
>
> I want to extract the bound [0, 1000), the loop variable "i" and the 
> loop body (sum += i).
> What should I do?
>
> I read the LLVM API document, and find some useful classes like 
> "Loop", "LoopInfo".
> But I do not know how to use them in detail.
>
> Could you please give me some help? A detailed usage may be more helpful.

I think you want to look at the LoopInfoWrapperPass (see the doxygen at 
http://llvm.org/doxygen/classllvm_1_1LoopInfoWrapperPass.html). Your 
pass will use the analysis results from LoopInfoWrapperPass to get 
references to LoopInfo objects which can then be used to find loops (if 
memory serves me correctly).

Regards,

John Criswell

> Thanks!
>
>
> Best wishes,
> Jia-Ju Bai
>
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-- 
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell