[llvm-dev] Why does new llvm-as reject old IR format?

[Madhur Amilkanthwar via llvm-dev]

Ok, Thanks a lot!

On Fri, Aug 12, 2016 at 7:42 PM, James Y Knight <jyknight at google.com> wrote:

> On Fri, Aug 12, 2016 at 10:05 AM, Madhur Amilkanthwar via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Surprised to know that backward compatibility is not honored across the
>> tools.
>> (i.e. you can read old .bc but NOT old .ll files)
>> Supporting latter is more useful, IMO, because then I wouldn't have to
>> modify all my sources.
>>
>
> It's been that way for LLVM's entire existence. One could imagine ways to
> allow for source-level IR compatibility as well, but, at the moment there
> isn't any such promise.
>
> See:
> http://llvm.org/docs/DeveloperPolicy.html#ir-backwards-compatibility
>
> And who are "we" here?
>>
>
> "We" is the LLVM community, since that is the official policy of the LLVM
> project.
>
>
>>  On Fri, Aug 12, 2016 at 7:21 PM, Tim Northover <t.p.northover at gmail.com>
>> wrote:
>>
> On 12 August 2016 at 06:42, Madhur Amilkanthwar via llvm-dev
>>> <llvm-dev at lists.llvm.org> wrote:
>>> > Ideally, I would expect backward compatibility from LLVM tools; and not
>>> > requiring to modify the code again.
>>> >
>>> > What is LLVM's philosophy here?
>>>
>>> We support backwards compatibility (i.e. newer tools can read older
>>> files) on .bc files but not .ll files. This goes back to version 3.0
>>> so nothing new can read files from the 2.9 or earlier era and the
>>> other direction (older tools reading newer files) is never going to
>>> work.
>>>
>>> We're in the middle of changing our version numbering and official
>>> policy, but the general sense is that we have no intent to break this.
>>>
>>> So for your particular problem you should be able to use a 3.2 llvm-as
>>> and then do what you like with the .bc file.
>>>
>>> Cheers.
>>>
>>> Tim.
>>>
>>
>>
>>
>> --
>> *Disclaimer: Views, concerns, thoughts, questions, ideas expressed in
>> this mail are of my own and my employer has no take in it. *
>> Thank You.
>> Madhur D. Amilkanthwar
>>
>>
>> _______________________________________________
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>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>


-- 
*Disclaimer: Views, concerns, thoughts, questions, ideas expressed in this
mail are of my own and my employer has no take in it. *
Thank You.
Madhur D. Amilkanthwar
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