<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Mar 3, 2021 at 3:23 PM Lang Hames <<a href="mailto:lhames@gmail.com">lhames@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi Dave, Stefan,<div><br></div><div>I'm in favor of a re-think of ORC layering. It may take some time to execute though.<br><div><br></div><div>In the short term I think we could fix this by moving JITSymbol to OrcShared, and making ExecutionEngine depend on OrcShared. Does anyone see any obvious problems with that? If not I can try to make that change some time in the next few weeks.</div></div></div></blockquote><div><br>Looks plausible to me.<br> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>Further thoughts, since this discussion reminded me of them:</div><div><br></div><div>Medium term I'd like to refactor JITSymbol.h:</div><div>- Replace JITTargetAddress (at least for Orc and JITLink use cases) with OrcTargetAddress, which should be a uint64_t wrapper with type safety to ensure that we don't perform bogus arithmetic operations like adding two addresses together.</div><div>- Rewrite JITSymbolFlags to avoid all the enum casting that it currently requires.</div><div>- Re-think JITEvaluatedSymbol -- it's *very* rare that anyone cares about the flags. Maybe ORC lookup should just return a map of OrcTargetAddresses.</div><div><br></div><div>Longer term I think ORC should be moved out of ExecutionEngine. With ORCv1 removed they're largely separate APIs now. The one sticking point would be RTDyldObjectLinkingLayer, which depends on RuntimeDyld and Orc. I think it would be reasonable to move this into its own library too.</div><div><br></div><div>-- Lang.<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Mar 4, 2021 at 9:49 AM David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr">On Wed, Mar 3, 2021 at 2:35 PM Stefan Gränitz <<a href="mailto:stefan.graenitz@gmail.com" target="_blank">stefan.graenitz@gmail.com</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
Yes, got it and I also wonder if there's a better low hanging
solution.<br>
<br>
The underlying question that I wanted to point out was: Would the
escape to Support be a one-time solution for JITSymbol or will we
see more of the same soon. GDB JIT interface seems to be the next
candidate, but OTOH it's quite a special case again. I will have a
look at OProfile and Perf implementations for RuntimeDyld to make a
better estimation.<br>
<br>
I guess you'd prefer us to act on it soon now?</div></blockquote><div><br>I'm not too pressed - Google's unblocked by lumping JITSymbol into Support (we can do this just in the build files without having to move the file around), but the sooner these things are resolved the better to avoid other things layering on top of them, etc.<br> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div> What time frame are
you having in mind? Is next week acceptable? (I am more or less ooo
for the rest of the week.)<br></div></blockquote><div><br>Sure<br> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div>
<br>
<blockquote type="cite">@Peter, @Nico: I've noticed your post-review
comments. I will have a look tonight (~10h from now).</blockquote>
These should be fixed now. Thanks again for reporting your issues
and sorry for the inconvenience.<br>
<br>
<div>On 03/03/2021 19:40, David Blaikie
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">To clarify, I'm not sure JITSymbol should be in
llvmSupport, but that it's the only place it can be right now
that would be correct. Maybe there's some other layering changes
(not necessarily introducing a new library, but possibly
changing other dependency edges, etc) - but maybe there's
already some JIT Stuff in llvmSupport and that's where it should
go. It's a simple enough header/wouldn't come at a great cost to
include it in Support.</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Mar 3, 2021 at 1:51 AM
Stefan Gränitz <<a href="mailto:stefan.graenitz@gmail.com" target="_blank">stefan.graenitz@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div> Hi David<br>
<br>
Thanks for the details. Yes, the layering issue is something
we should take care of soon. It also makes trouble for the
modules build (see: <a href="https://reviews.llvm.org/D95747" target="_blank">https://reviews.llvm.org/D95747</a>).<br>
<br>
I think we should split up the JITSymbol.h and move
JITTargetAddress into OrcShared. What remains would be the
JITSymbol class. Moving this one to Support sounds like a
nice solution to me.<br>
<br>
However, we have a similar situation with the GDB JIT
interface declarations. They should have their own header,
yes, but where would we put it? Support too? Not sure about
it. Having the definition only in OrcTargetProcess would be
acceptable IMHO. The only alternative seems to be an
entirely new library (as discussed in the review <a href="https://reviews.llvm.org/D97339" target="_blank">https://reviews.llvm.org/D97339</a>).<br>
<br>
What do you think?<br>
<br>
@Peter, @Nico: I've noticed your post-review comments. I
will have a look tonight (~10h from now).<br>
<br>
Best,<br>
Stefan<br>
<br>
<div>On 03/03/2021 04:57, David Blaikie wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Seems one of the latest Orc changes ( <a href="https://github.com/llvm/llvm-project/commit/99a6d003edbe97fcb94854547276ffad3382ec1d" target="_blank">https://github.com/llvm/llvm-project/commit/99a6d003edbe97fcb94854547276ffad3382ec1d</a>
) while not itself changing/breaking the layering in
LLVM's own build, it has revealed some pre-existing
problems with the layering that we'd worked around at
Google in a way that isn't viable after this recent
change.<br>
<br>
One immediate/easily observed issue:
lib/ExecutionEngine's CMakeLists.txt says it depends on
OrcTargetProcess, but OrcTargetProcess includes
lib/ExecutionEngine/JITSymbol.h<br>
<br>
The only common dependency for all the uses of
JITSymbol.h seems to be llvm/Support (ie: without
introducing new dependencies or new libraries,
JITSymbol.h would need to be moved to llvm/Support to
fix this particular dependency cycle/issue)<br>
<br>
We do have a bunch of other workarounds for Orc layering
in the Google internal build system too - so perhaps I
can enumerate some/all of the issues here, as it might
be best to take a holistic approach to fixing these
issues.<br>
<br>
Let's see what I can document/figure out... <br>
<br>
ExecutionEngine/Orc -> ExecutionEngine<br>
ExecutionEngine/Interpreter -> ExecutionEngine<br>
ExecutionEngine/RuntimeDyld -> ExecutionEngine<br>
ExecutionEngine/IntelJITEvents -> ExecutionEngine<br>
ExecutionEngine/OProfileJIT -> ExecutionEngine<br>
ExecutionEngine/PerfJITEvents -> ExecutionEngine<br>
ExecutionEngine/MCJIT -> ExecutionEngine<br>
<br>
And there's actually no #includes in ExecutionEngine
that reference those libraries, so that's pretty good.<br>
<br>
It is this CMakeLists.txt dependency from
ExecutionEngine to OrcTargetProcess. Which happens
without a #include:<br>
<br>
<p style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(0,0,0)"><span style="font-variant-ligatures:no-common-ligatures">$
grep -r "void __jit_debug_register_code" llvm/</span></p>
<p style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(219,39,218)"><span style="font-variant-ligatures:no-common-ligatures">llvm/lib/ExecutionEngine/GDBRegistrationListener.cpp</span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(56,185,199)">:</span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)"><span>
</span>extern "C" </span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(202,51,35)"><b>void
__jit_debug_register_code</b></span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)">();</span></p>
<p style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(219,39,218)"><span style="font-variant-ligatures:no-common-ligatures">llvm/lib/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.cpp</span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(56,185,199)">:</span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)">LLVM_ATTRIBUTE_NOINLINE
</span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(202,51,35)"><b>void
__jit_debug_register_code</b></span><span style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)">()
{</span></p>
<br>
Would be better if this wasn't declared arbitrarily
(instead, if it was declared in a header and defined as
usual, the circular dependence would be more clear, I
think?) - but either way, the circular dependency needs
to be fixed.<br>
<br>
- Dave<br>
<p style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(219,39,218)"><span style="font-variant-ligatures:no-common-ligatures;color:rgb(0,0,0)"><br>
<br>
</span></p>
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<pre cols="72">--
<a href="https://flowcrypt.com/pub/stefan.graenitz@gmail.com" target="_blank">https://flowcrypt.com/pub/stefan.graenitz@gmail.com</a></pre>
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