[LLVMdev] LLVM JIT Questions

[Eli Bendersky]

On Tue, Apr 23, 2013 at 10:39 AM, Kaylor, Andrew <andrew.kaylor at intel.com>wrote:

> Hi Dmitri,
>
> Regarding your first question, if you can use the MCJIT engine a caching
> mechanism will be available very soon.  I'm preparing to commit a patch
> today to add this capability.  I'm not sure what it would take to get
> something similar working with the older JIT engine.  I expect it would
> take a fair amount of work because the older JIT engine isn't designed
> around object loading as the MCJIT engine is.
>
>
I would expect it to be very hard to do with the old JIT, because it JITs
the machine code in a "loaded" form (absolute addresses put into the needed
places). This is tightly coupled with the current execution and does not
apply to other executions. MCJIT allows this by virtue of having a
not-yet-loaded ELF object which can be cached for later use. I imagine this
is what you do in your patch, Andy.

Eli






> Regarding your second question, there might be more than one way to do
> this, but once you have an llvm::Function (but before you JIT the code) you
> should be able to use llvm::Function::setCallingConv().
>
> -Andy
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
> Behalf Of Dmitri Rubinstein
> Sent: Tuesday, April 23, 2013 5:25 AM
> To: LLVM Dev
> Subject: [LLVMdev] LLVM JIT Questions
>
> Hi all,
>
> For my current project I need a couple of informations about JIT. I seen
> similar questions already, but the answers are a bit older and I hope
> somebody can provide me a recent information.
>
> 1. In my project I frequently construct LLVM IR, compile it and execute
> with JIT. Because the constructed IR is often the same (but can vary
> depending on input data) I would like to cache produced machine code on the
> disk. There is no JIT API for dumping and loading of compiled code.
>
> Are there any plans to add this feature in the near future ?
>
> How complex would it be to implement this for somebody who has only
> experience with LLVM code generation, but no deep knowledge of JIT
> internals ?
>
> 2. I also need to interface with C-libraries which are either loaded as a
> shared library or pre-compiled with clang and loaded as BC file.
> However, LLVM does not provide a way how to construct function signature
> compatible with the C-ABI of the specific platform. I know that clang
> library has internally this information, but I need this functionality
> without clang.
>
> Is there any documentation which describes how to do generate C-ABI
> compatible LLVM functions or code that implements this functionality ?
>
> Thanks,
>
> Dmitri
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130423/3ab956cb/attachment.html>