[LLVMdev] LLVM multithreading

[Jasmin Jahic]

Hello,

I'm performing certain analysis with LLVM and interpreter is more suitable.

Do you perhaps know is there a way to do things that I previously described
using interpreter?


On Fri, May 30, 2014 at 3:44 PM, David Chisnall <David.Chisnall at cl.cam.ac.uk
> wrote:

> Hi Jasmin,
>
> It would help if you would explain your reason for wanting to use the
> interpreter.  If you want threads, typically it is because you want
> performance and so it would make more sense to compile the bitcode once
> with the JIT in the main function and then call the various functions from
> your threads.
>
> David
>
> On 30 May 2014, at 14:28, Jasmin Jahic <jasmin.jahic at gmail.com> wrote:
>
> > Hello,
> >
> > thank you for your answers. I'll explain my problem with giving you a
> concrete details.
> >
> > I have a MAIN program which includes LLVM libraries and loads one bc
> file. From MAIN I execute different functions from the bc file using LLVM
> interpreter.  On the LLVM website it is said:
> > "LLVMContext is an opaque class in the LLVM API which clients can use to
> operate multiple, isolated instances of LLVM concurrently within the same
> address space." - It seems that this is not correct or I'm not
> understanding it properly.
> >
> > One context is used to create two modules, and based on modules all
> other things needed for the execution (engine builders, execution engines,
> functions). When functions are executed (sequentially), they are obviously
> executed in different memory space. I have verified this over access to the
> global variable.
> >
> > However, if functions are executed using the same execution engine
> (context, module and execution builder the same), then they are executed in
> the same memory space. But using one execution engine is not suitable for
> threads, because one execution engine means one stack.
> >
> > One option is to use different stack frames. Before trying that, I just
> wanted to ask is there a different way for sharing memory space between
> more execution engines?
> >
> > Best regards,
> > Jasmin JAHIC
> >
> >
> > On Fri, May 30, 2014 at 12:28 PM, Renato Golin <renato.golin at linaro.org>
> wrote:
> > On 30 May 2014 11:01, David Chisnall <David.Chisnall at cl.cam.ac.uk>
> wrote:
> > > I think your question is a result of misunderstanding the nature of
> LLVM.  It is not a virtual machine, it is an abstract machine and a set of
> tools implementing compilers for that abstract machine.  You don't run the
> bitcode (well, you can interpret it, but you don't usually), you compile
> the bitcode and then run the resulting code.  If you want to run the same
> code on all threads, then you just use the LLVM [MC]JIT to compile it once
> and then you call the generated functions from different threads.
> >
> > Try VMKit:
> >
> > http://vmkit.llvm.org/
> >
> > They may have answered your question already.
> >
> > --renato
> >
>
>
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