llvm dev - Apr 2013 - [LLVMdev] Memory clean for applications using LLVM for JIT compilation

On 14 Jan 2013, at 15:48, Reid Kleckner <rnk at google.com>
wrote:
> 
> Or maybe would it be possible to have a custom allocator for memory space
for the native code that we could provide? With this last option we would be
responsible for the clean up ourselves and just provide memory space to LLVM
where it can store the results.
> 
> Yes, you should be able to inherit from llvm::JITMemoryManager and do
something like this.
I've been trying to work with this solution, but it does pose a problem. The
problem is that we use an ExecutionEngine and set a memory manager with
setJITMemoryManager on EngineBuilder. The problem is that this means when the
ExecutionEngine is deallocated, it end up deallocating the memory manager.

I can understand doing this when the code sets up it's own memory manager,
but with an external memory manager, I'd expect LLVM not to deallocate that
object for me. Is there a way to prevent this from happening? I can't keep
the ExecutionEngine around here either, since EngineBuilder needs a Module,
which in it's turn needs an LLVMContext, which I'm trying to create for
each new request.

Does anyone have additional ideas for how to handle this? Or whether there is
another approach that could work here?

-- 
Dirkjan

Yeah, the JITMemoryManager appears to be owned by the EE and I cannot find a way
to get around it. I agree from an API design point of view a custom mgr should
be owned by the client code but that is not how it works right now.  You
probably have to copy out the JIT code into your own block of memory.

________________________________________
From: llvmdev-bounces at cs.uiuc.edu [llvmdev-bounces at cs.uiuc.edu] on behalf
of Dirkjan Bussink [d.bussink at gmail.com]
Sent: Sunday, January 20, 2013 6:54 AM
To: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Memory clean for applications using LLVM for JIT
compilation

On 14 Jan 2013, at 15:48, Reid Kleckner <rnk at google.com>
wrote:
>
> Or maybe would it be possible to have a custom allocator for memory space
for the native code that we could provide? With this last option we would be
responsible for the clean up ourselves and just provide memory space to LLVM
where it can store the results.
>
> Yes, you should be able to inherit from llvm::JITMemoryManager and do
something like this.
I've been trying to work with this solution, but it does pose a problem. The
problem is that we use an ExecutionEngine and set a memory manager with
setJITMemoryManager on EngineBuilder. The problem is that this means when the
ExecutionEngine is deallocated, it end up deallocating the memory manager.

I can understand doing this when the code sets up it's own memory manager,
but with an external memory manager, I'd expect LLVM not to deallocate that
object for me. Is there a way to prevent this from happening? I can't keep
the ExecutionEngine around here either, since EngineBuilder needs a Module,
which in it's turn needs an LLVMContext, which I'm trying to create for
each new request.

Does anyone have additional ideas for how to handle this? Or whether there is
another approach that could work here?

--
Dirkjan




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