[LLVMdev] lld file format as native OS executable format

[Shea Levy]

On 05/02/2012 12:59 PM, John Criswell wrote:
> On 5/2/12 10:29 AM, Shea Levy wrote:
>> Hello,
>>
>> Would it be feasible to use the internal lld file format as the native
>> executable format for an OS? Are there performance or space
>> considerations that would make this a poor choice?
>
> By lld, do you mean the LLVM IR bitcode format, or are you referring 
> to something else?

I meant the format used by the nascent lld project (lld.llvm.org). The 
scenario I had in mind would involve native code inside the relevant atoms.

>
> As far as using LLVM IR as a format for executables, there was a 
> research paper on that topic with an older version of LLVM 
> (http://llvm.org/pubs/2003-10-01-LLVA.html).  You'd probably want to 
> redo the experiments on file size and such since LLVM's on-disk format 
> has changed considerably over the years, but it might give you an idea 
> of what issues to consider and what trouble spots there might be.
>
> Also note that there's follow-on work to support an entire OS on the 
> LLVM IR without the inline assembly language feature.  Just look for 
> the publications written by me if you need that.
> :)
>
> The more significant challenge, I think, would be translating LLVM IR 
> to native code on-the-fly.  That'll add overhead; you will probably 
> want a way to cache native code for executables, and that adds some 
> new issues into OS design (such as how you securely fetch and update 
> the native code translations).
>
> To summarize, is it feasible?  Yes.  Is it a good idea?  I'm not 
> certain; it definitely depends on what environment your OS is going to 
> run in and what your goals are.
>
>>
>> Cheers,
>> Shea Levy
>>
>> P.S. please CC me on replies, I'm not subscribed.
>
> Please note that I had to approve your message to the mailing list.  
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>
> -- John T.
>
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