[LLVMdev] Metadata for Argument, BasicBlock

[Ralf Karrenberg]

Indeed, Nadav.
I also want to store information about loops as block-metadata of the 
loop header, but as you say this is easily doable by using block 
terminators.
However, for the divergence analysis, we cannot use the terminators, 
because the properties of a block are determined by multiple criterions.
If you do not want to introduce ugly dummy-calls to store that data (and 
write even more ugly code to find that call later etc.), you need block 
metadata.

On 5/8/12 8:45 AM, Rotem, Nadav wrote:
> If we were to implement the #unroll pragma, we would want to add metadata to loop headers.  But, it's not a big deal since we can simply add this metadata to block terminators.
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Dan Gohman
> Sent: Tuesday, May 08, 2012 00:58
> To: Ralf Karrenberg
> Cc: llvmdev at cs.uiuc.edu List
> Subject: Re: [LLVMdev] Metadata for Argument, BasicBlock
>
>
> On May 7, 2012, at 7:21 AM, Ralf Karrenberg<Chareos at gmx.de>  wrote:
>
>> Hi Duncan,
>>
>> On 5/6/12 6:12 PM, Duncan Sands wrote:
>>> Hi Ralf,
>>>
>>>> Is there a clean way to attach metadata nodes to Arguments and/or
>>>> BasicBlocks?
>>>
>>> not at the moment.  Feel free to work on adding this functionality!
>>
>> I am looking into that now.
>> I decided to temporarily go for the following syntax for BasicBlock
>> metadata (subject to discussion):
>>
>> entry:
>>      !property_1 !0, !property_2 !1
>>    %x = fadd float %a, %b
>>
>> It seems that I have to touch lots of files for this:
>> BasicBlock.h/.cpp, Metadata.cpp, LLParser.cpp, AsmParser, AsmWriter,
>> BitcodeReader.cpp, BitcodeWriter.cpp so far.
>> I basically went and duplicated code that handles metadata attached to
>> instructions.
>
> What kind of things might basic block metadata be used for?
>
> Dan
>
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