llvm dev - Jun 2014 - [LLVMdev] Any way get debug output of generated assembly from MCJIT without completely redoing CodeGen?

Yeah, that's probably how I'd do it.

Might be useful if you guys want to contribute that as a command line
option Kevin.

-eric

On Tue, Jun 24, 2014 at 3:03 PM, Kevin Modzelewski <kmod at dropbox.com>
wrote:
> We do this in Pyston using a JITEventListener that just disassembles the
> output; it's "it works let's move on"-quality:
> https://github.com/dropbox/pyston/blob/master/src/codegen/dis.cpp
>
> I'm not sure how efficient the disassembling is, but at least the
process is
> pretty self-contained.
>
>
> On Tue, Jun 24, 2014 at 1:33 PM, Craig Smith <craig at ni.com> wrote:
>>
>>
>> Hello all,
>>
>> I'm trying to hack MCJIT::emitObject to optionally output the
>> corresponding text assembly associated with the object code being
emitted
>> (if a debug flag is set in the app/dev environment which is hosting
LLVM).
>> I attempted to do this by adding another AsmPrinter pass to the
>> PassManager, but this runs into all sorts of problems because
there's only
>> once MCContext and one MachneModuleInfo pass maintaining various state
>> information (MCSections, MCSymbols, etc.) and the two AsmPrinter passes
>> interfere with each other.
>>
>> The only way I've been able to get this to work is to create an
entirely
>> separate PassManager, and use addPassesToEmitFile() on it, which will
redo
>> the entire CodeGen process again unnecessarily.
>> Does anyone have any ideas/pointers on how I might do this efficiently?
>> This is only for a debugging aid, but I'd like to not have to
compile
>> everything twice when it's enabled.
>>
>> Thanks
>> Craig
>>
>>
>> _______________________________________________
>> 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
>

Hi Craig,

I am trying to JIT PHP code and this is a hack ..
https://github.com/sathvikl/llvm/blob/master/lib/ExecutionEngine/OProfileJIT/OProfileJITEventListener.cpp

It writes out file of JITed methods in /tmp using the OProfileJIT interface
so if you register via the OProfile interface
+ JITEventListener *event_listener
JITEventListener::createOProfileJITEventListener()
+ llvm_engine->RegisterJITEventListener(event_listener)

and run oprofile, it will dump out the file with JITed methods into a file.
If you use a disassembler, you can try libxed
https://github.com/facebook/hhvm/blob/10b2a6a3a8075b676ea167ea49e6bba5b8cca68e/hphp/util/disasm.cpp
shows how to use it.
libxed is packaged here -
https://software.intel.com/en-us/articles/pin-a-binary-instrumentation-tool-downloads

I plan to write a cleaner interface for this so you can view it via perf
but didn't get to it.

sathvik




On Tue, Jun 24, 2014 at 4:03 PM, Eric Christopher <echristo at gmail.com>
wrote:
> Yeah, that's probably how I'd do it.
>
> Might be useful if you guys want to contribute that as a command line
> option Kevin.
>
> -eric
>
> On Tue, Jun 24, 2014 at 3:03 PM, Kevin Modzelewski <kmod at
dropbox.com>
> wrote:
> > We do this in Pyston using a JITEventListener that just disassembles
the
> > output; it's "it works let's move on"-quality:
> > https://github.com/dropbox/pyston/blob/master/src/codegen/dis.cpp
> >
> > I'm not sure how efficient the disassembling is, but at least the
> process is
> > pretty self-contained.
> >
> >
> > On Tue, Jun 24, 2014 at 1:33 PM, Craig Smith <craig at ni.com>
wrote:
> >>
> >>
> >> Hello all,
> >>
> >> I'm trying to hack MCJIT::emitObject to optionally output the
> >> corresponding text assembly associated with the object code being
> emitted
> >> (if a debug flag is set in the app/dev environment which is
hosting
> LLVM).
> >> I attempted to do this by adding another AsmPrinter pass to the
> >> PassManager, but this runs into all sorts of problems because
there's
> only
> >> once MCContext and one MachneModuleInfo pass maintaining various
state
> >> information (MCSections, MCSymbols, etc.) and the two AsmPrinter
passes
> >> interfere with each other.
> >>
> >> The only way I've been able to get this to work is to create
an entirely
> >> separate PassManager, and use addPassesToEmitFile() on it, which
will
> redo
> >> the entire CodeGen process again unnecessarily.
> >> Does anyone have any ideas/pointers on how I might do this
efficiently?
> >> This is only for a debugging aid, but I'd like to not have to
compile
> >> everything twice when it's enabled.
> >>
> >> Thanks
> >> Craig
> >>
> >>
> >> _______________________________________________
> >> 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
> >
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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This actually came up today in a related conversation I had with David Blaikie
about RuntimeDyld testing.

As Eric suggested, it would be nice to have a command line flag for something
like this. I'd prefer to just dump objects to disk by default though, rather
than disassemble them: Once they're dumped they can be disassembled and
poked at via existing tools at leisure.

Cheers,
Lang.

Sent from my iPad
> On Jun 24, 2014, at 6:09 PM, sathvik <sathvikl at gmail.com> wrote:
> 
> Hi Craig,
> 
> I am trying to JIT PHP code and this is a hack ..
>
https://github.com/sathvikl/llvm/blob/master/lib/ExecutionEngine/OProfileJIT/OProfileJITEventListener.cpp
> 
> It writes out file of JITed methods in /tmp using the OProfileJIT interface
so if you register via the OProfile interface
> + JITEventListener *event_listener =
JITEventListener::createOProfileJITEventListener()
> + llvm_engine->RegisterJITEventListener(event_listener) 
> 
> and run oprofile, it will dump out the file with JITed methods into a file.
If you use a disassembler, you can try libxed
>
https://github.com/facebook/hhvm/blob/10b2a6a3a8075b676ea167ea49e6bba5b8cca68e/hphp/util/disasm.cpp
> shows how to use it. 
> libxed is packaged here - 
>
https://software.intel.com/en-us/articles/pin-a-binary-instrumentation-tool-downloads
> 
> I plan to write a cleaner interface for this so you can view it via perf
but didn't get to it.
> 
> sathvik 
>  
> 
> 
> 
>> On Tue, Jun 24, 2014 at 4:03 PM, Eric Christopher <echristo at
gmail.com> wrote:
>> Yeah, that's probably how I'd do it.
>> 
>> Might be useful if you guys want to contribute that as a command line
>> option Kevin.
>> 
>> -eric
>> 
>> On Tue, Jun 24, 2014 at 3:03 PM, Kevin Modzelewski <kmod at
dropbox.com> wrote:
>> > We do this in Pyston using a JITEventListener that just
disassembles the
>> > output; it's "it works let's move on"-quality:
>> > https://github.com/dropbox/pyston/blob/master/src/codegen/dis.cpp
>> >
>> > I'm not sure how efficient the disassembling is, but at least
the process is
>> > pretty self-contained.
>> >
>> >
>> > On Tue, Jun 24, 2014 at 1:33 PM, Craig Smith <craig at
ni.com> wrote:
>> >>
>> >>
>> >> Hello all,
>> >>
>> >> I'm trying to hack MCJIT::emitObject to optionally output
the
>> >> corresponding text assembly associated with the object code
being emitted
>> >> (if a debug flag is set in the app/dev environment which is
hosting LLVM).
>> >> I attempted to do this by adding another AsmPrinter pass to
the
>> >> PassManager, but this runs into all sorts of problems because
there's only
>> >> once MCContext and one MachneModuleInfo pass maintaining
various state
>> >> information (MCSections, MCSymbols, etc.) and the two
AsmPrinter passes
>> >> interfere with each other.
>> >>
>> >> The only way I've been able to get this to work is to
create an entirely
>> >> separate PassManager, and use addPassesToEmitFile() on it,
which will redo
>> >> the entire CodeGen process again unnecessarily.
>> >> Does anyone have any ideas/pointers on how I might do this
efficiently?
>> >> This is only for a debugging aid, but I'd like to not have
to compile
>> >> everything twice when it's enabled.
>> >>
>> >> Thanks
>> >> Craig
>> >>
>> >>
>> >> _______________________________________________
>> >> 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
>> >
>> _______________________________________________
>> 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
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