llvm dev - Aug 2013 - [LLVMdev] Metadata in the backend

Hi all,

I'm looking for a way to insert metadata into an
instruction/function/basic-block in the IR level, and afterwards reading it in
the backend (ARM to be exact).



So my questions are:

1.       Does/can the metadata in the IR survive the code-generator in some way?

2.       Is there a general of 'communication' between the optimizer and
the backend?



Thanks!

Alon
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Hi Alon, 

There is no good mapping between IR-level instructions and MachineInstructions
because we don’t do a 1:1 translation. We delete instructions and create new
ones. Some of the memory operations hold references to the original IR pointer,
but we drop this information in many places. We also delete or generate new
basic blocks, so you can’t rely on that. However, from the MachineFunction you
can access the original IR and access some metadata (which you can place on the
terminator of the first basic block of something).  I am not sure how much
information you want to communicate between the IR-level passes and the backend,
but you can introduce new intrinsics that can be lowered to pseudo instructions.

Thanks,
Nadav  

On Aug 8, 2013, at 5:30 AM, Alon Shaltiel (ashaltie) <ashaltie at
cisco.com> wrote:
> Hi all,
> I'm looking for a way to insert metadata into an
instruction/function/basic-block in the IR level, and afterwards reading it in
the backend (ARM to be exact).
>  
> So my questions are:
> 1.       Does/can the metadata in the IR survive the code-generator in some
way?
> 2.       Is there a general of ‘communication’ between the optimizer and
the backend?
>  
> Thanks!
> Alon
> _______________________________________________
> 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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