[LLVMdev] Using llvm Metadata inside llc

[Michael D'Hont]

Hi

As i didn't get any respons I am reformulating my question in the hope to
make myself more clear.
Has anyone an idea how to use metadata present in the llvm ir to guide the
if-conversion in llc (as metadata get's dropped during SelectionDAG) ?

-Michael




2013/4/13 Michael D'Hont <michael.dhont at ugent.be>

> The project I am working on is to use the llvm toolchain for embedded CGRA
> processors .
> This however poses some restrictions on the block formation, because
> modulo scheduling is applied in a later stage.
> For this reason the idea was to create custom pragma's to generate
> metadata and attach it to de branches of loops we wanted to map on a cgra
> module.
> It is a lot similar to the loop parallell metadata discussed previously on
> the mailing list.
> I was able to made the metadata survive opt passes by extending LoopInfo
> to remove/restore metadata as needed but once at the backend I get stuck.
>
> I was thinking to add some custom fields to SDNode and afterwards MI but
> that doesn't seem efficient (or a good idea) for many reason's.
> For example not each instruction has metadata attached (in my case it's
> only branching instructions inside a loop) and also during the
> pattern matching nodes are replaced/combined/etc. and thus the data also
> gets removed.
>
> I need the information within the metadata to force if-conversion on
> specific parts of the code for hyperblock formation.
>
>
> 2013/4/12 Eric Christopher <echristo at gmail.com>
>
>> There's some support for metadata on MI and definitely on the IR. What
>> do you have in mind and what are you doing?
>>
>> -eric
>>
>> On Fri, Apr 12, 2013 at 7:37 AM, Michael D'Hont <michael.dhont at ugent.be>
>> wrote:
>> > Is there any way to work with the metadata inside llc? Or is there a
>> > specific reason why metadata is not supported inside llc? Because as I
>> see
>> > it the metadata get's completely removed during instruction selection.
>> >
>> > I would like to use the metadata to influence Loop Specific
>> transformations
>> > and if-conversion.
>> >
>> > Kind Regards
>> > Michael D'hont
>> >
>> > _______________________________________________
>> > 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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