llvm dev - Oct 2014 - [LLVMdev] extending LLVM - basic block reordering

​Hi.
I want to change order of code basic blocks in memory. I visited "
http://llvm.org/docs/ExtendingLLVM.html" page and it advised me to ask it
before any effort.
What parts of LLVM help me and how? I am a newbie on LLVM.
Thanks.
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Dear Zahra,

To reorder basic blocks, all you need to do is to write an LLVM pass 
that changes the order that the block appear within the list of basic 
blocks that belong to the function.  The only block you can't reorder is 
the entry block which, I think, always needs to be the first basic block 
in the list.

The first thing you should do is read the document "Writing an LLVM 
Pass" (http://llvm.org/docs/WritingAnLLVMPass.html).  You should also 
read the "LLVM Programmer's Manual" 
(http://llvm.org/docs/ProgrammersManual.html).  To look up specific 
information on LLVM classes, use doxygen 
(http://llvm.org/doxygen/hierarchy.html).

The first coding task would be to write a skeleton FunctionPass and run 
it through the opt program.  After that, you should be able to add code 
to your FunctionPass to reorder the basic blocks within a function.

Regards,

John Criswell


On 10/5/14, 11:34 AM, Zahra fatehi marj wrote:
> Hi.
> I want to change order of code basic blocks in memory. I visited 
> "http://llvm.org/docs/ExtendingLLVM.html" page and it advised me 
> to ask it before any effort.
> What parts of LLVM help me and how? I am a newbie on LLVM.
> Thanks.
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

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

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Thank you for the very useful guidance. It helped me. I understood
http://llvm.org/docs/WritingAnLLVMPass.html and
http://llvm.org/docs/CMake.html#cmake-out-of-source-pass and applied to my
pass. But I have another problem. After any change in pass, I must build
LLVM again? It takes a long time. Is there a way to build only pass?

Thanks again.
​

On Tue, Oct 7, 2014 at 2:47 AM, John Criswell <jtcriswel at gmail.com>
wrote:
>  Dear Zahra,
>
> To reorder basic blocks, all you need to do is to write an LLVM pass that
> changes the order that the block appear within the list of basic blocks
> that belong to the function.  The only block you can't reorder is the
entry
> block which, I think, always needs to be the first basic block in the list.
>
> The first thing you should do is read the document "Writing an LLVM
Pass" (
> http://llvm.org/docs/WritingAnLLVMPass.html).  You should also read the
> "LLVM Programmer's Manual"
(http://llvm.org/docs/ProgrammersManual.html).
> To look up specific information on LLVM classes, use doxygen (
> http://llvm.org/doxygen/hierarchy.html).
>
> The first coding task would be to write a skeleton FunctionPass and run it
> through the opt program.  After that, you should be able to add code to
> your FunctionPass to reorder the basic blocks within a function.
>
> Regards,
>
> John Criswell
>
>
>
> On 10/5/14, 11:34 AM, Zahra fatehi marj wrote:
>
>  ​ Hi.
> I want to change order of code basic blocks in memory. I visited "
> http://llvm.org/docs/ExtendingLLVM.html" page and it advised me to ask
it
> before any effort.
> What parts of LLVM help me and how? I am a newbie on LLVM.
> Thanks.
>
>
> _______________________________________________
> LLVM Developers mailing listLLVMdev at cs.uiuc.edu        
http://llvm.cs.uiuc.eduhttp://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
>
> --
> John Criswell
> Assistant Professor
> Department of Computer Science, University of
Rochesterhttp://www.cs.rochester.edu/u/criswell
>
>
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