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<p class="MsoNormal"><span lang="EN-GB" style="mso-fareast-language:EN-US">Thank you David!<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">ORC leader is actually a pretty cool title. Anyway – what is the Clang AST? Maybe I could try converting from a string to that AST myself? Currently I use the way you described, by getting
the name from the LLVM 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"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> David Blaikie <dblaikie@gmail.com>
<br>
<b>Sent:</b> 25 September 2019 17:45<br>
<b>To:</b> Gaier, Bjoern <Bjoern.Gaier@horiba.com>; Lang Hames <lhames@gmail.com><br>
<b>Cc:</b> llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [llvm-dev] Questions after playing around with KaleidoscopeJIT (With source files)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB">(+Lang, ORC leader)<br>
<br>
I don't know much about most of the questions myself, though for (5) - Clang does map between code and mangled names, but it doesn't provide a simple entry-point to that. (mostly because it's not often useful in isolation) - you can compile "const int foo;"
to LLVM IR and you'll see the mangled name there. The narrowest piece of code that gives just the mangled name would accept the Clang AST as input and operate on that, not on a string of source code.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB">On Wed, Sep 25, 2019 at 2:37 AM Gaier, Bjoern via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Hello LLVM people,<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">after finishing Chapter 1 and 2 of the KaleidoscopeJIT tutorial, I started to play around with the code and now, I have even more questions than before. I hope
that the people reading this could help me with it, to improve my understanding about the LLVM and the JIT.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">I have also the source code and binaries (Windows) available but because I don't know how the mailing list treats attachments (like .zip) I decided to only attach
the source files - hoping it will help >o<<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">---<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">1.) Resolving undefined references<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">I wonder what the best practice is to resolve symbols that are not defined in my llvm::Module.
<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">For that purpose I created "CM_ExternalConstant", that is using "extern const int planschiValue;" and compiled it with Clang. (See CM_ExternalConstant.cpp)<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">"planschiValue" is not defined in the module, so it will be unreferenced when I jit it. What is the best way to do this? I used 3 different ways:<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">1.) I went over the llvm::Module before adding it to the layers. I searched for the symbol "?planschiValue@@3HB" and called "replaceAllUsesWith" to replace the
symbol with the correct address. (See PlanschbeckenJIT.cpp:31)<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">2.) I set my own GeneratorFunction and provided addresses for the symbols (See PlanschbeckenJIT.cpp:95)<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">3.) I can use this->es.getMainJITDylib().define<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Each way worked fine. But I felt that way 2.) was the most annoying way, because I had to provide many other addresses. So what way is the best? Or can I 'freely'
choose?<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Is it possible to have multiple GeneratorFunctions? I would like to use the 'default' DynamicLibrarySearchGenerator plus my own lookup function.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Would it also be possible to replace the uses of "?planschiValue@@3HB" directly with the actuall value of "plaschiValue"? Because it is a constant?<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">2.) Loading multiple modules<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">I created "CM_Orc", which has a function "int helloOrc()" - "CM_ExternalConstant" has the same function, but a different implementation. (See CM_Orc.cpp and CM_ExternalConstant.cpp)
Adding both modules to the JIT will lead to an error message:<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">"Failure value returned from cantFail wrapped call<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">UNREACHABLE executed at c:\program files\llvm\include\llvm\support\error.h:708!"<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">I always thought that in this situation, one of the functions would be renamed...<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">3.) Loading multiple modules - controlled resolving<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Finally I created "CM_PlanschiValue" this file defines a value for "planschiValue" that was referenced in "CM_ExternalConstant". (See CM_ PlanschiValue.cpp and
CM_ExternalConstant.cpp) Surprisingly, if I wrote:<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">"const int planschiValue = 543210;"<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Clang would not generate code for it.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">But when writing:<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">"extern const int planschiValue = 543210;" it worked. Why? Why can Clang optimize away the code, when it could be referenced by a different module? Like it was!<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">I loaded "CM_ExternalConstant" and "CM_PlanschiValue" together, while using my own GeneratorFunction. But there was no need any more to provide an address for
"?planschiValue@@3HB". Obviously, the two modules where linked - which is correct. But what, if I don't want that for whatever reason? Would I have to rename the referenced value in the llvm::Module before adding the second module? Or should I run instead
two different JITs?<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">The idea behind this is... what should I do if I have multiple modules, that are not meant to be used together but should run in the same process.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">4.) Clang and JIT optimization<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">If I compile my modules with Clang and all optimizations turned on - do I still need the TransformLayer in my JIT?<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">5.) Mangling names<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Does Clang or the LLVM provide a function to mangle from the string "const int planschiValue;" to "?planschiValue@@3HB"? Or vice versa?<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">---<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">I know that this are a lot questions and that I'm not good in explaining stuff - but I really hope you guys can help me to understand everything better.<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Kind greetings and many thanks<o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span lang="EN-US">Björn<o:p></o:p></span></p>
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