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<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Hey Lang,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">> </span>
<span lang="EN-GB">Do you mean that the object file is produced by another process and is being loaded into your JIT process for execution, or that you want your JIT to produce code for several different processes? These are different problems with different
solutions. I'll wait until I understand your use case to answer further.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">In the current state we don’t have a JIT only an handcrafted object loader. All our object files are pre-compiled but will be loaded by different processes into the same shared memory
for the main process to execute them.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">We would like to still have the files pre-compiled but we want to remove the handcrafted object loader. However, since we already create those files with Clang, it is not such a big
change to compile them to IR.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">> </span>
<span lang="EN-GB">You're trying to do all this on Hard Mode. ;)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Yeah it was a silly thought… sorry xO<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">> </span>
<span lang="EN-GB">The part of your use case that is the most opaque to me is the renaming. When you see a reference to "test" in some object, how do you decide that it should resolve to the definition of "test" in, for example, Planschi, as opposed to some
other module? Do you just have a list of modules that you check in-order until you find a matching symbol name?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">You wouldn’t find a reference to “test”, you would find “Planschi_test”. We would first try resolving that with the standard C library functions. If this fails, then we will ask the
object file “Planschi” if it has “test” and resolve it. If “Planschi” is not loaded for some reason, then we go on with the next symbol and mark “Planschi_test” as undefined. So… we fail linking. However, our code allows to just try the linking again – so
we do and do until it succeeds. Only when the undefined references hit 0 we mark the object file as executable. However, if the module you depend on has still undefined references you can be screwed. Cause our code will not check the dependencies. Another
reason why we want to move away.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">I think… but this is probably not thought through well:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">I need to do those steps on the IR level now – because the DefinitionGenerator needs to resolve all symbols, but I might have to wait for a different module to pop up first.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">So I would iterate over the globals and the functions of the Module:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">I would rename each symbol I encounter to have a unique name.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">This would be easy because when we load stuff, we give them a hierarchical name like “Parent_Child_Child_Dino”<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">So </span>
<span lang="EN-GB">"?Sampler@@YAXXZ" Could be renamed to "</span><span lang="EN-GB" style="mso-fareast-language:EN-US">Parent_Child_Child_Dino_</span><span lang="EN-GB">?Sampler@@YAXXZ".<br>
<br>
If I encounter an undefined reference that is not part of the standard library like "?_Plansch_test@@3HA" Then I would extract the relative path and convert it to an absolute one, getting: “Parent_Child__Plansch_? test@@3HA”. When the “Plansch” module was loaded,
I would have give it an unique name as well so they would fit. I would then add them to there own DyLibs and would be happy… would I?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">1.) When all symbols have such a unique name now, couldn’t I just add them all to the same DyLib and use the RessourceTracker to unload them later? This would spare me searching the right DyLibs.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">2.) Can I ask a DyLib if it has something for the “Parent_Child__Plansch_? test@@3HA" loaded?<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:35.4pt"><span lang="EN-GB">My biggest worry is, I do all those fancy renaming and such, but I still have no guarantee that the missing symbols are already present, but when I look up my symbols of interest it is to late…
cause if something is missing because the module was not loaded yet, then I get in an error state and I’m stuck there :c<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">3.) Isn’t the process of renaming those symbols like… really memory costly? Could I run into limitations of creating a too long function name?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">I hope that makes sense… cause I’m not good in explaining anything, especially not when it is in a different language :c<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Thank you again :D
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Kind greetings<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Björn<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Lang Hames <lhames@gmail.com>
<br>
<b>Sent:</b> 29 September 2020 18:55<br>
<b>To:</b> Gaier, Bjoern <Bjoern.Gaier@horiba.com><br>
<b>Cc:</b> LLVM Developers Mailing List <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [llvm-dev] ORC JIT - different behaviour of ExecutionSession.lookup?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi Bjoern,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">However, another thing of our system is, that each object file was loaded from a different process,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Do you mean that the object file is produced by another process and is being loaded into your JIT process for execution, or that you want your JIT to produce code for several different processes? These are different problems with different
solutions. I'll wait until I understand your use case to answer further.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Writing this… I actually wondered about something else but this feels like a terrible approach… But now I’m curious xD<br>
So… if I load an IR-Module, could I use the static LLVM compiler to compile it to an object file and then use the source code of the LLD to load and resolve the symbols the same way/kind we did in the past?<br>
That sounds more like the “addObjectFile” function of the LLJIT… And then I guess I have to write a LinkLayer or something? That is where my knowledge ends…<br>
Disclaimer: I don’t like that approach but it would be interesting to know (also cause some people here would be happy with it .w.”)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">You're trying to do all this on Hard Mode. ;)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">ORC takes care of all this kind of stuff for you:<o:p></o:p></p>
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<p class="MsoNormal"> Don't re-write IR. Leave references as symbolic -- they will be fixed up in the JIT linker.<o:p></o:p></p>
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<p class="MsoNormal"> You don't need to write your own JIT linker. LLJIT has one built in.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">When you add things to the JIT:<o:p></o:p></p>
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<p class="MsoNormal"> - If you have a program representation (module, object file, etc.) and you want to add it then just go ahead.<o:p></o:p></p>
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<p class="MsoNormal"> - If your program representations contain external references then they must be resolvable or linking will fail (there's no getting around that, in a JIT or in a regular compile), BUT...<o:p></o:p></p>
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<p class="MsoNormal"> - You can always add new definitions in response to a query by using a definition generator. If your definition generator can find/create a definition then great. If it can't then the reference really is unresolved and linking really
should fail.<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">The part of your use case that is the most opaque to me is the renaming. When you see a reference to "test" in some object, how do you decide that it should resolve to the definition of "test" in, for example, Planschi, as opposed to some
other module? Do you just have a list of modules that you check in-order until you find a matching symbol name?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-- Lang.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Tue, Sep 29, 2020 at 2:30 AM Gaier, Bjoern <<a href="mailto:Bjoern.Gaier@horiba.com">Bjoern.Gaier@horiba.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Hey Lang,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Thank you for your help and your patience – also for your answers in the “ORC JIT - Can modules independently managed with one LLJIT instance? + problems with
ExecutionSession.lookup” mail. Both problems have the same origin so I keep writing about it here, to avoid duplication.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">My big problem is still handling cross references between modules with “our” name scheme. Since our old loader loads object files, we resolved those references
with object files and since they were already compiled, we knew all addresses right away. With the LLJIT as I finally understand, I will only get the addresses when I have resolved every references, which makes the code way safer.
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">However, another thing of our system is, that each object file was loaded from a different process, so sometimes not all symbols for ModuleA were present because
ModuleB was not loaded/requested yet. That was okay, so we kept resolving the undefined references of ModuleA until ModuleB was loaded and everything was fine.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">If I get it right… This would change now to having a single LLJIT representing the entire system. Each process would get it’s own DyLib for there module. However,
I would need to check on IR-Level now which symbols would be undefined – correct? Because if I wait until “DefinitionGenerator::tryToGenerate” is called and have to wait for a module that might never be loaded, then I’m stuck there forever.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">1.) If I find a symbol that is undefined – and it has our name scheme, then I would jump to for example ModuleB, which is also not jitted yet and would do a “replaceAllUsesWith”
on the Symbol of ModuleA to ModuleB – right? </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> - Would that mean, when I add ModuleA to DyLibA – is ModuleB then part of DyLibA as well?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">1.1.) Alternatively I could rename the symbol</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">2.) If the ModuleB is already jitted, then I can take the address to do the “replaceAllUsesWith” right?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">When I resolved all those references, then I can add the IR Module to my DyLib and compile it. However is it a good idea to use “replaceAllUsesWith” with addresses?
Seems like the DefinitionGenerator would be jobless…</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Writing this… I actually wondered about something else but this feels like a terrible approach… But now I’m curious xD</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">So… if I load an IR-Module, could I use the static LLVM compiler to compile it to an object file and then use the source code of the LLD to load and resolve the
symbols the same way/kind we did in the past?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">That sounds more like the “addObjectFile” function of the LLJIT… And then I guess I have to write a LinkLayer or something? That is where my knowledge ends…<br>
Disclaimer: I don’t like that approach but it would be interesting to know (also cause some people here would be happy with it .w.”)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Thank you so far!</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Kind greetings</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Björn</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Lang Hames <<a href="mailto:lhames@gmail.com" target="_blank">lhames@gmail.com</a>>
<br>
<b>Sent:</b> 29 September 2020 01:47<br>
<b>To:</b> Gaier, Bjoern <<a href="mailto:Bjoern.Gaier@horiba.com" target="_blank">Bjoern.Gaier@horiba.com</a>><br>
<b>Cc:</b> LLVM Developers Mailing List <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>><br>
<b>Subject:</b> Re: [llvm-dev] ORC JIT - different behaviour of ExecutionSession.lookup?</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi Bjoern,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Even though the "tryToGenerate" function of my DefinitionGenerator returned a "llvm::orc::SymbolsNotFound" for the "?_Plansch_test@@3HA", I got an address for "?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">That's because you're issuing the lookup with RequiredState == SymbolState::Resolved. This means that your query will return as soon as "?Sampler@@YAXXZ" is assigned an address.
In the JIT linker(s) addresses are assigned before external references are looked up. So after your lookup returns the linker attempts to find "?_Plansch_test@@3HA", fails, and so moves "?Sampler@@YAXXZ" to the error state.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">You almost always want to issue your lookups with RequiredState == SymbolState::Ready. This ensures that the query will not return until / unless the requested symbols (and all
their dependencies) are successfully linked into the target process and ready to execute.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Question 1.)<br>
Is there any way to reset the error state of "?Sampler@@YAXXZ" at this point?</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">No. However, the removable code feature will allow you to remove failed materialization units once it lands in the mainline.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">- After my first call I used the "define" function of the JITDylib to define ?_Plansch_test@@3HA and then I tried calling the lookup function again and again,
however I only got the error: "Failed to materialize symbols" even though "?_Plansch_test@@3HA" was defined now...<br>
- Changing the order of the "define" and the "lookup" call works of course, but I'm interested in the case where I don't know the address yet.</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">The JIT doesn't re-try linking. Once a symbol has failed to link it remains in the error state. In theory, once removable code is added you could choose to remove
and then re-add "?Sampler@@YAXXZ" after "?_Plansch_test@@3HA" is defined. The real solution though is just to make sure that "?_Plansch_test@@3HA" is defined (either directly or via a generator) before you look up "?Sampler@@YAXXZ".</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Out of curiosity I repeated the previous scenario - but added "?_Plansch_test@@3HA" to the "lookupSet" which changed things drasticly. When executing "lookup"
I now get the "llvm::orc::SymbolsNotFound" error from my DefinitionGenerator...</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Yes. Because "?_Plansch_test@@3HA" is not defined. You should see a SymbolsNotFound error sent to your error reporter in the first scenario too, followed by a
failure-to-materialize error for "?Sampler@@YAXXZ".</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">... and "?Sampler@@YAXXZ" is stuck as a pending query in the MaterializingInfos entries.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Huh. That sounds like a bug: All references to the query should be removed from the state machine before it returns its result (in this case an error). I'll see
if I can reproduce this locally and fix it up, but it doesn't affect the discussion here.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">When I then add a definition for "?_Plansch_test@@3HA" and call "lookup" the second time, it will succeed and give me the addresses. Also I'm able to execute the code now. This
is great! However...<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">When a lookup fails we try to restore the ExecutionSession state to what it was prior to the query. This is why the sequence "lookup -> symbols not found -> define -> lookup again"
worked.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Question 2.)<br>
Why did the first call to lookup not return the address of "?Sampler@@YAXXZ" like in the first scenario? I expected it would return an address for it.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">A lookup must match against all symbols before anything is JIT'd. When it failed to match "?_Plansch_test@@3HA" we immediately bailed out with an error. There was no further attempt
to compile "?Sampler@@YAXXZ".<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Question 3.)<br>
Can I somehow combine both behaviours? Getting the address for all the symbols (like in scenario 1) while still being able to provide definitions later (like in scenario 2)?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><i>Sort of.</i><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Definition generators allow you to provide a definition at the last minute (i.e. in response to a query). The best mental model though is: "All definitions that a generator can
generate are part of the interface of the dylib". E.g. if you use a DynamicLibrarySearchGenerator to mirror symbols from a dynamic library containing "foo", "bar" and "baz" then you should think of your JITDylib as containing definitions for "foo", "bar" and
"baz", even if the generator hasn't actually added them to the JITDylib yet. The reason is that it will add them in response to any query for them, so it's indistinguishable (except for timing and debug logging) from the case where they're already present.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">If you need to be able to defer adding a "real" definition beyond the initial lookup then your only option (and this only applies to functions) is a lazy-reexport. This allows you
to provide a definition for a function while deferring lookup until the first execution of the re-export at runtime. I wouldn't generally use this to break dependencies though: You want a definition of the real function body for "?_Plansch_test@@3HA" already
added to your JIT because (in general) you never know when JIT'd code will need it.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">My turn to ask a question: How is "?_Plansch_test@@3HA" created, and why not just add it up-front? :)<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">-- Lang.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">On Mon, Sep 28, 2020 at 4:57 AM Gaier, Bjoern via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Hey everyone,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">I felt this question is different from my other question - hope this is okay.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">So - I was playing around with the lookup function of the ExecutionSession and there are some things I don't understand.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">I have a .BC file with a function "?Sampler@@YAXXZ" referencing a value "?_Plansch_test@@3HA" that is not defined in that module itself. I first planed on not
providing an address for "?_Plansch_test@@3HA" but wanted to know the address of "?Sampler@@YAXXZ". So I issued something like that:</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> auto &ES = this->jit->getExecutionSession();</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> SymbolLookupSet lookupSet;</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> lookupSet.add("?Sampler@@YAXXZ", llvm::orc::SymbolLookupFlags::WeaklyReferencedSymbol);</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> ES.lookup({{&jit->getMainJITDylib(), llvm::orc::JITDylibLookupFlags::MatchAllSymbols}}, lookupSet, llvm::orc::LookupKind::Static, llvm::orc::SymbolState::Resolved);</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Even though the "tryToGenerate" function of my DefinitionGenerator returned a "llvm::orc::SymbolsNotFound" for the "?_Plansch_test@@3HA", I got an address for
"?Sampler@@YAXXZ". Dumping the "MainJITDylib" I saw, that the "?Sampler@@YAXXZ" was in an Error state. Which made sense - I guess.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Question 1.)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Is there any way to reset the error state of "?Sampler@@YAXXZ" at this point?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">- After my first call I used the "define" function of the JITDylib to define ?_Plansch_test@@3HA and then I tried calling the lookup function again and again,
however I only got the error: "Failed to materialize symbols" even though "?_Plansch_test@@3HA" was defined now...</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">- Changing the order of the "define" and the "lookup" call works of course, but I'm interested in the case where I don't know the address yet.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Out of curiosity I repeated the previous scenario - but added "?_Plansch_test@@3HA" to the "lookupSet" which changed things drasticly. When executing "lookup"
I now get the "llvm::orc::SymbolsNotFound" error from my DefinitionGenerator and "?Sampler@@YAXXZ" is stuck as a pending query in the MaterializingInfos entries. When I then add a definition for "?_Plansch_test@@3HA" and call "lookup" the second time, it will
succeed and give me the addresses. Also I'm able to execute the code now. This is great! However...</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Question 2.)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Why did the first call to lookup not return the address of "?Sampler@@YAXXZ" like in the first scenario? I expected it would return an address for it.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Question 3.)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Can I somehow combine both behaviours? Getting the address for all the symbols (like in scenario 1) while still being able to provide definitions later (like
in scenario 2)?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Thank you in advance and kind greetings,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-GB">Björn</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert,
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">_______________________________________________<br>
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<p class="MsoNormal">Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Heiko Lampert, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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