llvm dev - Feb 2013 - [LLVMdev] CostModelAnalysis for 3.0 release

Hi All,
I wanted to do some basic cost estimation of Instruction/BB.
There're CostModelAnalysis and CodeMetrics available in 3.1 and 3.2
releases.
I've been using 3.0 for a while. I'm wondering whether similar analysis
can
be done in the old 3.0 release, e.g. back porting the implementation.

Thank you!

Best,
Ryan
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Hi Ryan, 

I think that it would be difficult to back port the CostModel back to LLVM3.0
because it uses the new TargetTransformInfo analysis.  I also wanted to mention
that only _lowering_ passes (target-specific optimization passes) may use TTI
and the cost model. Higher-level canonicalization passes should not use it.

Thanks,
Nadav

On Feb 6, 2013, at 1:26 AM, ryan <stdstack at gmail.com> wrote:
> Hi All,
> I wanted to do some basic cost estimation of Instruction/BB. There're
CostModelAnalysis and CodeMetrics available in 3.1 and 3.2 releases.
> I've been using 3.0 for a while. I'm wondering whether similar
analysis can be done in the old 3.0 release, e.g. back porting the
implementation.
> 
> Thank you!
> 
> Best,
> Ryan
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Thanks a lot for the reply, Nadav!
I see that using the cost model in target-independent analysis is not good.
But I really like the idea of having instruction
cost estimation available. Also the reason I can't directly move to 3.2
code base is that it fails to compile(produce bc files) big
project like MySQL, where 3.0 has no problem.

Right now, I'm trying to hard code a particular target, and copy part of
the TargetTransformInfo and X86TargetTransformInfo
to a simple LLVM 3.0 project to try out. So far I'm stuck in
instantiating X86TargetMachine and wondering whether it can be
created from instances of TargetMachine or TargetData.

Thank you!

Best Regards,
Ryan
On Thu, Feb 7, 2013 at 10:45 AM, Nadav Rotem <nrotem at apple.com> wrote:
> Hi Ryan,
>
> I think that it would be difficult to back port the CostModel back to
> LLVM3.0 because it uses the new TargetTransformInfo analysis.  I also
> wanted to mention that only _lowering_ passes (target-specific optimization
> passes) may use TTI and the cost model. Higher-level canonicalization
> passes should not use it.
>
> Thanks,
> Nadav
>
> On Feb 6, 2013, at 1:26 AM, ryan <stdstack at gmail.com> wrote:
>
> > Hi All,
> > I wanted to do some basic cost estimation of Instruction/BB.
There're
> CostModelAnalysis and CodeMetrics available in 3.1 and 3.2 releases.
> > I've been using 3.0 for a while. I'm wondering whether similar
analysis
> can be done in the old 3.0 release, e.g. back porting the implementation.
> >
> > Thank you!
> >
> > Best,
> > Ryan
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
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