[cfe-dev] JIT - Resolve obj file without a main

[via cfe-dev]

Hello Lang,

so you are part of the "Jitter-Team"?
I'm really interested in this whole jitting-process. I wanted to know, is 
there a way to load other obj-files, than the one created with clang? 
Could I load - for example - a obj-File from VisualStudio? Or will the 
namemangeling fail?

Kind regards
Björn



From:   Lang Hames <lhames at gmail.com>
To:     bjoern.gaier at horiba.com
Cc:     Clang Dev <cfe-dev at lists.llvm.org>, LLVM Developers Mailing List 
<llvm-dev at lists.llvm.org>
Date:   24.05.2017 01:19
Subject:        Re: JIT - Resolve obj file without a main



Hi Bjoern,

Could you please tell me, if there is a way to allocate the memory for the 
codemodules more precise? I would like to allocate the memory for strings 
from a separated memory-pool. But how can I detect a string? The only 
moment I can do this is in "notifyObjectLoaded" via the names of the 
symbols. But than it is impossible for my to get the address of the 
symbols. I noticed that some strings are stored in .rdata, but this is no 
guarantee. 

There is no easy way to do this at the moment, any it will always be 
limited by what the object format allows (as you said: you need the object 
format to tell you what's a string and what isn't, and they don't do that 
in all situations).

If you can identify strings at the IR level you could do this by 
allocating the strings in your own memory and marking the IR definitions 
as weak, but this would also require LLVM to be more careful about picking 
strong definitions, so it would require some non-trivial LLVM 
improvements. These improvements are on the drawing board, but there is no 
schedule for them to be implemented yet.

Cheers,
Lang.

On Wed, May 17, 2017 at 7:03 AM, <bjoern.gaier at horiba.com> wrote:
Hi Lang, 

I'm using Windows. I was parsing an IR-File and added the Module to the 
ExectuionEngine. If I than searched for a function, I just got 0. But when 
the module had a main, I got an address. I solved the problem via a call 
to "generateCodeForModule". The JIT didn't even called my SymbolResolver 
in this special case. 

Could you please tell me, if there is a way to allocate the memory for the 
codemodules more precise? I would like to allocate the memory for strings 
from a separated memory-pool. But how can I detect a string? The only 
moment I can do this is in "notifyObjectLoaded" via the names of the 
symbols. But than it is impossible for my to get the address of the 
symbols. I noticed that some strings are stored in .rdata, but this is no 
guarantee. 

Kind regards 
Björn 



From:        Lang Hames <lhames at gmail.com> 
To:        bjoern.gaier at horiba.com 
Cc:        Clang Dev <cfe-dev at lists.llvm.org>, LLVM Developers Mailing 
List <llvm-dev at lists.llvm.org> 
Date:        16.05.2017 18:37 
Subject:        Re: JIT - Resolve obj file without a main 




Hi Björn, 

I don't recall ever seeing this behavior before. Can you describe the 
situation in more detail? 

Is this specifically for object files loaded via 
RTDyldLinkingLayer::addObjectSet, or does it apply to IR Modules without a 
main too? 

When you say the JIT won't resolve an address, do you mean that you can't 
find anything when you call findSymbol on the JIT, or that the JIT isn't 
calling your SymbolResolver back to find addresses? 

Was this for MacOS, Linux, or Windows? 

Cheers, 
Lang.  

On Fri, May 12, 2017 at 6:47 AM, <bjoern.gaier at horiba.com> wrote: 
Hello Lang, 

I noticed, if I load a obj-File without a main-function, the Jitter won't 
resolve any address. But if I have a main, everything works fine. Why is 
this so? Is there a way to stop this? 

Kind regards 
Björn
Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, 
USt.ID-Nr. DE 114 165 789
Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode, Heiko 
Lampert, Takashi Nagano, Takeshi Fukushima. 



Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, 
USt.ID-Nr. DE 114 165 789
Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode, Heiko 
Lampert, Takashi Nagano, Takeshi Fukushima.



Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, 
USt.ID-Nr. DE 114 165 789
Geschäftsführer: Hiroshi Kawamura, Dr Hiroshi Nakamura, Markus Bode, Heiko 
Lampert, Takashi Nagano, Takeshi Fukushima.
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