[LLVMdev] Dynamically loading native code generated from LLVM IR

[Malea, Daniel]

Take a look at the MCJIT unit tests under unittests/ExecutionEngine/MCJIT

The MCJITTestBase class does the majority of the interactions with the LLVM API you're referring to.

Good luck,
Dan

On 2012-10-13, at 4:57 AM, "Armin Steinhoff" <as at steinhoff-automation.com> wrote:

> 
> Kaylor,
> 
> do you have some good documented example code which shows the usage of the MCJIT ?
> This would help a lot ... the sematic of lots of API calls are not intuitively understandable.
> 
> Best Regards
> 
> --Armin
> 
> 
> 
> Kaylor, Andrew wrote:
>> I'm not sure I understand your use case, but MCJIT (as opposed to the legacy JIT) does almost exactly what you're asking for.  It generates an in-memory object file image (using addPassesToEmitMC) and then loads and links it for execution.
>> 
>> If there's some particular detail you don't like in the way this is happening, you might be able to generate a file as you have and then use the RuntimeDyld interface to load it.  The llvm-rtdyld tool does something like this.
>> 
>> -Andy
>> 
>> -----Original Message-----
>> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Baris Aktemur
>> Sent: Thursday, October 11, 2012 11:58 PM
>> To: llvmdev at cs.uiuc.edu
>> Subject: [LLVMdev] Dynamically loading native code generated from LLVM IR
>> 
>> Hi,
>> 
>> I'm building LLVM IR. I'd like to compile this IR to native code (I don't want JIT) and immediately load it to execute. So far, I've the following:
>> 
>> 1) I can emit the IR to native assembly/object file doing the same thing llc does (using TargetMachine::addPassesToEmitFile).
>> 2) I can dynamically load a precompiled .so file (using llvm::sys::DynamicLibrary::getPermanentLibrary), get a function pointer from that file, and execute.
>> 
>> I can't dynamically load the .o file I produce in step 1 because it's a static library. If I could produce a .so file in step 1, my problem would be solved. llc has a "-relocation-model=pic" option, but the file produced with that did not dynamically load. I got lost in clang's options when trying to find where the "-shared" and "-fPIC" options are used.
>> 
>> So, my question is: Which API should I look at to emit dynamically loadable native code from LLVM IR?
>> 
>> I would also like to emit code to an in-memory stream instead of a file because everything happens at runtime, but that's a secondary concern.
>> 
>> Thanks in advance.
>> 
>> -Baris Aktemur
>> 
>> 
>> 
>> 
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