llvm dev - Oct 2017 - Debugging JIT'ed code with ORC JIT?

Hi Connor,

...The LLVM documentation has a page at
>     llvm.org/docs/DebuggingJITedCode.html
> showing an example of using gdb to debug MCJIT’ed code, but has no mention
> of ORC JIT.

What debugging support MCJIT has is provided by the RuntimeDyld utility,
which ORC shares. I would expect anything in that document to apply to ORC
as well, though I haven't tested it personally.

For what it's worth, this is something I'm interested in and hope to
make
some progress on in tree in the not too distant future.

-- Lang.

On Mon, Oct 9, 2017 at 12:27 PM, Jameson Nash via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> That is correct – there is no built-in support. You have to provide your
> own Registrar to the ObjectLinkingLayer to provide this sort of
> functionality. (For example JuliaLang does that at https://github.com/
> JuliaLang/julia/blob/1216e5f60cd2b23e29856b5227399a
> b0f3abef76/src/jitlayers.cpp#L437, in addition to registering the
> function pointer and object file info in several other places).
>
>
> On Sun, Oct 8, 2017 at 11:48 PM Connor Gray via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi,
>>
>> I’m wondering if it’s possible to debug code JIT’ed with the newer ORC
>> JIT. The LLVM documentation has a page at
>>
>>     llvm.org/docs/DebuggingJITedCode.html
>>
>> showing an example of using gdb to debug MCJIT’ed code, but has no
>> mention of ORC JIT.
>>
>> From searching around online I’ve gotten the impression that ORC JIT
does
>> *not* support providing debugging information to attached debuggers,
but no
>> definitive source. Is it the case that ORC JIT in fact does support
>> debugging, and if so, are there examples available; or is my initial
>> impression correct?
>>
>> Thanks,
>> Connor
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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> What debugging support MCJIT has is provided by the RuntimeDyld utility,
> which ORC shares. I would expect anything in that document to apply to ORC
> as well, though I haven't tested it personally.
I'm pretty sure that's not the case, at least not with any simple
orcjit tutorials I've seen.

The GDB support is provided by `GDBJITRegistrationListener` which is
registered to MCJIT directly in the constructor and AFAICT no where
else. Also, since there doesn't seem to be a default (non-noop)
implementation of `ExecutionEngine::RegisterJITEventListener` I
believe you can't just call `RegisterJITEventListener` on non-MCJIT
and expect it to work.

So while I totally believe one can use
`JITEventListener::createGDBRegistrationListener()` to hook the JIT
with the the gdb registration function, it won't work without writing
code to explicitly do that (in additional to actually writing code to
interface with the event listener directly). OTOH though when using
MCJIT, this is done by default and one don't need to write any code
for it to work.
>
> For what it's worth, this is something I'm interested in and hope
to make
> some progress on in tree in the not too distant future.
>
> -- Lang.
>
> On Mon, Oct 9, 2017 at 12:27 PM, Jameson Nash via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>>
>> That is correct – there is no built-in support. You have to provide
your
>> own Registrar to the ObjectLinkingLayer to provide this sort of
>> functionality. (For example JuliaLang does that at
>>
https://github.com/JuliaLang/julia/blob/1216e5f60cd2b23e29856b5227399ab0f3abef76/src/jitlayers.cpp#L437,
>> in addition to registering the function pointer and object file info in
>> several other places).
>>
>>
>> On Sun, Oct 8, 2017 at 11:48 PM Connor Gray via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>>>
>>> Hi,
>>>
>>> I’m wondering if it’s possible to debug code JIT’ed with the newer
ORC
>>> JIT. The LLVM documentation has a page at
>>>
>>>     llvm.org/docs/DebuggingJITedCode.html
>>>
>>> showing an example of using gdb to debug MCJIT’ed code, but has no
>>> mention of ORC JIT.
>>>
>>> From searching around online I’ve gotten the impression that ORC
JIT does
>>> *not* support providing debugging information to attached
debuggers, but no
>>> definitive source. Is it the case that ORC JIT in fact does support
>>> debugging, and if so, are there examples available; or is my
initial
>>> impression correct?
>>>
>>> Thanks,
>>> Connor
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

HI Yichao,

RTDyldObjectLinkingLayer has a NotifyObjectLoaded hook that you can use to
call NotifyObjectEmitted on your GDBRegistrationListener.

If code is going to be unloaded we would have to add an extra hook to call
NotifyFreeingObject -- that seems totally reasonable to add.

-- Lang.


On Wed, Oct 11, 2017 at 10:44 AM, Yichao Yu <yyc1992 at gmail.com> wrote:
> > What debugging support MCJIT has is provided by the RuntimeDyld
utility,
> > which ORC shares. I would expect anything in that document to apply to
> ORC
> > as well, though I haven't tested it personally.
>
> I'm pretty sure that's not the case, at least not with any simple
> orcjit tutorials I've seen.
>
> The GDB support is provided by `GDBJITRegistrationListener` which is
> registered to MCJIT directly in the constructor and AFAICT no where
> else. Also, since there doesn't seem to be a default (non-noop)
> implementation of `ExecutionEngine::RegisterJITEventListener` I
> believe you can't just call `RegisterJITEventListener` on non-MCJIT
> and expect it to work.
>
> So while I totally believe one can use
> `JITEventListener::createGDBRegistrationListener()` to hook the JIT
> with the the gdb registration function, it won't work without writing
> code to explicitly do that (in additional to actually writing code to
> interface with the event listener directly). OTOH though when using
> MCJIT, this is done by default and one don't need to write any code
> for it to work.
>
> >
> > For what it's worth, this is something I'm interested in and
hope to make
> > some progress on in tree in the not too distant future.
> >
> > -- Lang.
> >
> > On Mon, Oct 9, 2017 at 12:27 PM, Jameson Nash via llvm-dev
> > <llvm-dev at lists.llvm.org> wrote:
> >>
> >> That is correct – there is no built-in support. You have to
provide your
> >> own Registrar to the ObjectLinkingLayer to provide this sort of
> >> functionality. (For example JuliaLang does that at
> >>
https://github.com/JuliaLang/julia/blob/1216e5f60cd2b23e29856b5227399a
> b0f3abef76/src/jitlayers.cpp#L437,
> >> in addition to registering the function pointer and object file
info in
> >> several other places).
> >>
> >>
> >> On Sun, Oct 8, 2017 at 11:48 PM Connor Gray via llvm-dev
> >> <llvm-dev at lists.llvm.org> wrote:
> >>>
> >>> Hi,
> >>>
> >>> I’m wondering if it’s possible to debug code JIT’ed with the
newer ORC
> >>> JIT. The LLVM documentation has a page at
> >>>
> >>>     llvm.org/docs/DebuggingJITedCode.html
> >>>
> >>> showing an example of using gdb to debug MCJIT’ed code, but
has no
> >>> mention of ORC JIT.
> >>>
> >>> From searching around online I’ve gotten the impression that
ORC JIT
> does
> >>> *not* support providing debugging information to attached
debuggers,
> but no
> >>> definitive source. Is it the case that ORC JIT in fact does
support
> >>> debugging, and if so, are there examples available; or is my
initial
> >>> impression correct?
> >>>
> >>> Thanks,
> >>> Connor
> >>> _______________________________________________
> >>> LLVM Developers mailing list
> >>> llvm-dev at lists.llvm.org
> >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >>
> >>
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> llvm-dev at lists.llvm.org
> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >>
> >
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >
>
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