[LLVMdev] lld file format as native OS executable format

[John Criswell]

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?

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.  It 
is better if you subscribe and then disable delivery of messages.  I 
usually only approve messages from non-subscribers once in the morning 
when I receive an email about the pending requests from yesterday.

-- John T.

> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev