llvm dev - Sep 2020 - LLVM Developers Meeting JIT BoF -- Request for Topics of Interest

Hi Geoff,

Importing symbols into the JIT from an object file or static library...?


Sure! Are you interested in doing this with the C API, LLJIT, or raw OrcV2
components?

The high-level answer here (which we can dig into further in the BoF) is:

For object files:
- For raw OrcV2 components you'll want to create an
RTDyldObjectLinkingLayer or ObjectLinkingLayer and use the 'add' method.
- For an LLJIT instance you can just call the 'addObjectFile' method.
- For the OrcV2 C API you can call the 'LLVMOrcLLJITAddObjectFile'
function.

For static libraries:
- For raw OrcV2 components or an LLJIT instance you can attach a
StaticLibraryDefinitionGenerator [1] to the JITDylib that you would like to
load the library into. See [2] for an example.
- For the OrcV2 C API we will just need to add a method to wrap the
operation above. We already have
'LLVMOrcCreateDynamicLibrarySearchGeneratorForProcess'. We should add
counterparts to that to load dynamic and static libraries from paths.

-- Lang.

[1]
https://github.com/llvm/llvm-project/blob/5aa56b242951ab0f0181386ea58509f19b09206e/llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h#L361
[2]
https://github.com/llvm/llvm-project/blob/e7549dafcd33ced4280a81ca1d1ee4cc78ed253f/llvm/tools/lli/lli.cpp#L968


On Mon, Sep 28, 2020 at 7:18 AM Geoff Levner <glevner at gmail.com> wrote:
> Importing symbols into the JIT from an object file or static library...?
>
> On Mon, Sep 28, 2020 at 5:29 AM Lang Hames <lhames at gmail.com>
wrote:
>
>> Hi Andres,
>>
>> A topic that I'd find interesting is what it'd take to make it
easier to
>>> use profile guided optimization in the context of JIT.  A few years
back
>>> I crudely hacked this together, but it was fairly ugly. It'd be
nice to
>>> make that easier.  Possibly too complicated for that type of
session?
>>
>>
>> We couldn't go into detail, but we could kick off a discussion and
>> identify who is interested in working on this. My pitch: We should
solve
>> this by investing in JITLink and implementing profiling (and debugger
>> support) via ObjectLinkingLayer::Plugins. Maybe a brief overview of /
>> discussion on how these work would be useful?
>>
>> -- Lang.
>>
>>
>> On Fri, Sep 25, 2020 at 7:19 PM Andres Freund <andres at
anarazel.de> wrote:
>>
>>> Hi,
>>>
>>> On 2020-09-25 19:05:42 -0700, Lang Hames wrote:
>>> > The 2020 Virtual LLVM Developer's Meeting is coming up the
week after
>>> next.
>>> > I'll be hosting a JIT Birds-of-a-Feather session on
Thursday the 8th at
>>> > 10:55am PDT (See http://llvm.org/devmtg/2020-09/schedule/).
I'm
>>> planning to
>>> > run this more like a Round Table: Minimal introduction, plenty
of time
>>> for
>>> > discussion.
>>> >
>>> > Does anyone have any LLVM JIT related topics that they would
>>> particularly
>>> > like to discuss at this session? Any questions that they think
could be
>>> > best answered by a round-table style discussion? I'll aim
to rope in
>>> the
>>> > right people and prepare answers to make sure we get the most
out of
>>> the
>>> > session.
>>>
>>> A topic that I'd find interesting is what it'd take to make
it easier to
>>> use profile guided optimization in the context of JIT.  A few years
back
>>> I crudely hacked this together, but it was fairly ugly. It'd be
nice to
>>> make that easier.  Possibly too complicated for that type of
session?
>>>
>>> I dimly recall that the main issue was that there is no good way to
>>> extract the profile information without going through files /
applying
>>> the profile data without going through files.
>>>
>>> Greetings,
>>>
>>> Andres Freund
>>>
>>
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We use LLJIT. Do addObjectFile() and StaticLibraryDefinitionGenerator
work for ELF objects?

On Mon, Sep 28, 2020 at 10:57 PM Lang Hames <lhames at gmail.com>
wrote:
>
> Hi Geoff,
>
>> Importing symbols into the JIT from an object file or static
library...?
>
>
> Sure! Are you interested in doing this with the C API, LLJIT, or raw OrcV2
components?
>
> The high-level answer here (which we can dig into further in the BoF) is:
>
> For object files:
> - For raw OrcV2 components you'll want to create an
RTDyldObjectLinkingLayer or ObjectLinkingLayer and use the 'add' method.
> - For an LLJIT instance you can just call the 'addObjectFile'
method.
> - For the OrcV2 C API you can call the 'LLVMOrcLLJITAddObjectFile'
function.
>
> For static libraries:
> - For raw OrcV2 components or an LLJIT instance you can attach a
StaticLibraryDefinitionGenerator [1] to the JITDylib that you would like to load
the library into. See [2] for an example.
> - For the OrcV2 C API we will just need to add a method to wrap the
operation above. We already have
'LLVMOrcCreateDynamicLibrarySearchGeneratorForProcess'. We should add
counterparts to that to load dynamic and static libraries from paths.
>
> -- Lang.
>
> [1]
https://github.com/llvm/llvm-project/blob/5aa56b242951ab0f0181386ea58509f19b09206e/llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h#L361
> [2]
https://github.com/llvm/llvm-project/blob/e7549dafcd33ced4280a81ca1d1ee4cc78ed253f/llvm/tools/lli/lli.cpp#L968
>
>
> On Mon, Sep 28, 2020 at 7:18 AM Geoff Levner <glevner at gmail.com>
wrote:
>>
>> Importing symbols into the JIT from an object file or static
library...?
>>
>> On Mon, Sep 28, 2020 at 5:29 AM Lang Hames <lhames at gmail.com>
wrote:
>>>
>>> Hi Andres,
>>>
>>>> A topic that I'd find interesting is what it'd take to
make it easier to
>>>> use profile guided optimization in the context of JIT.  A few
years back
>>>> I crudely hacked this together, but it was fairly ugly.
It'd be nice to
>>>> make that easier.  Possibly too complicated for that type of
session?
>>>
>>>
>>> We couldn't go into detail, but we could kick off a discussion
and identify who is interested in working on this. My pitch: We should solve
this by investing in JITLink and implementing profiling (and debugger support)
via ObjectLinkingLayer::Plugins. Maybe a brief overview of / discussion on how
these work would be useful?
>>>
>>> -- Lang.
>>>
>>>
>>> On Fri, Sep 25, 2020 at 7:19 PM Andres Freund <andres at
anarazel.de> wrote:
>>>>
>>>> Hi,
>>>>
>>>> On 2020-09-25 19:05:42 -0700, Lang Hames wrote:
>>>> > The 2020 Virtual LLVM Developer's Meeting is coming up
the week after next.
>>>> > I'll be hosting a JIT Birds-of-a-Feather session on
Thursday the 8th at
>>>> > 10:55am PDT (See
http://llvm.org/devmtg/2020-09/schedule/). I'm planning to
>>>> > run this more like a Round Table: Minimal introduction,
plenty of time for
>>>> > discussion.
>>>> >
>>>> > Does anyone have any LLVM JIT related topics that they
would particularly
>>>> > like to discuss at this session? Any questions that they
think could be
>>>> > best answered by a round-table style discussion? I'll
aim to rope in the
>>>> > right people and prepare answers to make sure we get the
most out of the
>>>> > session.
>>>>
>>>> A topic that I'd find interesting is what it'd take to
make it easier to
>>>> use profile guided optimization in the context of JIT.  A few
years back
>>>> I crudely hacked this together, but it was fairly ugly.
It'd be nice to
>>>> make that easier.  Possibly too complicated for that type of
session?
>>>>
>>>> I dimly recall that the main issue was that there is no good
way to
>>>> extract the profile information without going through files /
applying
>>>> the profile data without going through files.
>>>>
>>>> Greetings,
>>>>
>>>> Andres Freund

Hi Geoff,

We use LLJIT. Do addObjectFile() and StaticLibraryDefinitionGenerator
work
> for ELF objects?

They do. :)

I've not tested StaticLibraryDefinitionGenerator extensively on Linux. but
we have a regression test checking basic usage. If you run into any trouble
at all please file a bug and assign it to me.

-- Lang.



On Mon, Sep 28, 2020 at 2:05 PM Geoff Levner <glevner at gmail.com> wrote:
> We use LLJIT. Do addObjectFile() and StaticLibraryDefinitionGenerator
> work for ELF objects?
>
> On Mon, Sep 28, 2020 at 10:57 PM Lang Hames <lhames at gmail.com>
wrote:
> >
> > Hi Geoff,
> >
> >> Importing symbols into the JIT from an object file or static
library...?
> >
> >
> > Sure! Are you interested in doing this with the C API, LLJIT, or raw
> OrcV2 components?
> >
> > The high-level answer here (which we can dig into further in the BoF)
is:
> >
> > For object files:
> > - For raw OrcV2 components you'll want to create an
> RTDyldObjectLinkingLayer or ObjectLinkingLayer and use the 'add'
method.
> > - For an LLJIT instance you can just call the 'addObjectFile'
method.
> > - For the OrcV2 C API you can call the
'LLVMOrcLLJITAddObjectFile'
> function.
> >
> > For static libraries:
> > - For raw OrcV2 components or an LLJIT instance you can attach a
> StaticLibraryDefinitionGenerator [1] to the JITDylib that you would like to
> load the library into. See [2] for an example.
> > - For the OrcV2 C API we will just need to add a method to wrap the
> operation above. We already have
> 'LLVMOrcCreateDynamicLibrarySearchGeneratorForProcess'. We should
add
> counterparts to that to load dynamic and static libraries from paths.
> >
> > -- Lang.
> >
> > [1]
>
https://github.com/llvm/llvm-project/blob/5aa56b242951ab0f0181386ea58509f19b09206e/llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h#L361
> > [2]
>
https://github.com/llvm/llvm-project/blob/e7549dafcd33ced4280a81ca1d1ee4cc78ed253f/llvm/tools/lli/lli.cpp#L968
> >
> >
> > On Mon, Sep 28, 2020 at 7:18 AM Geoff Levner <glevner at
gmail.com> wrote:
> >>
> >> Importing symbols into the JIT from an object file or static
library...?
> >>
> >> On Mon, Sep 28, 2020 at 5:29 AM Lang Hames <lhames at
gmail.com> wrote:
> >>>
> >>> Hi Andres,
> >>>
> >>>> A topic that I'd find interesting is what it'd
take to make it easier
> to
> >>>> use profile guided optimization in the context of JIT.  A
few years
> back
> >>>> I crudely hacked this together, but it was fairly ugly.
It'd be nice
> to
> >>>> make that easier.  Possibly too complicated for that type
of session?
> >>>
> >>>
> >>> We couldn't go into detail, but we could kick off a
discussion and
> identify who is interested in working on this. My pitch: We should solve
> this by investing in JITLink and implementing profiling (and debugger
> support) via ObjectLinkingLayer::Plugins. Maybe a brief overview of /
> discussion on how these work would be useful?
> >>>
> >>> -- Lang.
> >>>
> >>>
> >>> On Fri, Sep 25, 2020 at 7:19 PM Andres Freund <andres at
anarazel.de>
> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> On 2020-09-25 19:05:42 -0700, Lang Hames wrote:
> >>>> > The 2020 Virtual LLVM Developer's Meeting is
coming up the week
> after next.
> >>>> > I'll be hosting a JIT Birds-of-a-Feather session
on Thursday the
> 8th at
> >>>> > 10:55am PDT (See
http://llvm.org/devmtg/2020-09/schedule/). I'm
> planning to
> >>>> > run this more like a Round Table: Minimal
introduction, plenty of
> time for
> >>>> > discussion.
> >>>> >
> >>>> > Does anyone have any LLVM JIT related topics that
they would
> particularly
> >>>> > like to discuss at this session? Any questions that
they think
> could be
> >>>> > best answered by a round-table style discussion?
I'll aim to rope
> in the
> >>>> > right people and prepare answers to make sure we get
the most out
> of the
> >>>> > session.
> >>>>
> >>>> A topic that I'd find interesting is what it'd
take to make it easier
> to
> >>>> use profile guided optimization in the context of JIT.  A
few years
> back
> >>>> I crudely hacked this together, but it was fairly ugly.
It'd be nice
> to
> >>>> make that easier.  Possibly too complicated for that type
of session?
> >>>>
> >>>> I dimly recall that the main issue was that there is no
good way to
> >>>> extract the profile information without going through
files / applying
> >>>> the profile data without going through files.
> >>>>
> >>>> Greetings,
> >>>>
> >>>> Andres Freund
>
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