llvm dev - Jul 2017 - loop induction variables at IR level

Hi,

I was looking at trying to get loop induction variable at IR level. LLVM
documentation mentioned indvars pass and getCanonicalInductionVariable() to
get them, I tried running the indvars pass and then a custom pass which
iterates through loops and uses the function to obtain variable for a
simple loop program. But the API returns null. I also read in similar posts
that the indvars pass is not available in the current version but
documentation still mentions them.

Is there something I am missing in my method , or is there an alternative
method to get the induction variable in the latest version.

Thanks in advance

Regards
Archa
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Hi, Archa,

What do you want to do with the induction variable? For most uses cases, 
you can use the ScalarEvolution analysis (and, if necessary, the 
ScalarEvolutionExpander).

  -Hal

On 07/01/2017 03:56 AM, Archa . via llvm-dev wrote:
> Hi,
>
> I was looking at trying to get loop induction variable at IR level. 
> LLVM documentation mentioned indvars pass and 
> getCanonicalInductionVariable() to get them, I tried running the 
> indvars pass and then a custom pass which iterates through loops and 
> uses the function to obtain variable for a simple loop program. But 
> the API returns null. I also read in similar posts that the indvars 
> pass is not available in the current version but documentation still 
> mentions them.
>
> Is there something I am missing in my method , or is there an 
> alternative method to get the induction variable in the latest version.
>
> Thanks in advance
>
> Regards
> Archa
>
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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Hi,

My understanding of induction variable is that it drives the loop with
fixed increment and by comparing it based on a condition (Hope I understood
it right). I want to extract and print this variable and what it is
compared to.

I have been trying to understand the ScalarEvolution and SCEVexpander
through llvm documentation are there any examples on how it is used,
because I have not been able to understand its usage properly.

Thanks and Regards
Archa
On 01-Jul-2017 3:54 pm, "Hal Finkel" <hfinkel at anl.gov> wrote:
> Hi, Archa,
>
> What do you want to do with the induction variable? For most uses cases,
> you can use the ScalarEvolution analysis (and, if necessary, the
> ScalarEvolutionExpander).
>
>  -Hal
> On 07/01/2017 03:56 AM, Archa . via llvm-dev wrote:
>
> Hi,
>
> I was looking at trying to get loop induction variable at IR level. LLVM
> documentation mentioned indvars pass and getCanonicalInductionVariable()
> to get them, I tried running the indvars pass and then a custom pass which
> iterates through loops and uses the function to obtain variable for a
> simple loop program. But the API returns null. I also read in similar posts
> that the indvars pass is not available in the current version but
> documentation still mentions them.
>
> Is there something I am missing in my method , or is there an alternative
> method to get the induction variable in the latest version.
>
> Thanks in advance
>
> Regards
> Archa
>
>
>
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at
lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
> --
> Hal Finkel
> Lead, Compiler Technology and Programming Languages
> Leadership Computing Facility
> Argonne National Laboratory
>
>
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