<div dir="ltr">The issue is probably that the analyses are not being cleared between runs and you end up using stale analyses. I'd recommend that you use a new instance of all the pass/analysis managers every time you perform codegen. (if you really want, you could call the `clear()` method on all the¬†analysis managers, but that's a bit more sketchy)<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Oct 16, 2021 at 5:37 PM Sanket Diwale via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</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"><p style="margin-top:0px;margin-right:0px;margin-left:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,system-ui,"Segoe UI","Liberation Sans",sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(231,233,235);background-color:rgb(45,45,45)">I am currently writing a frontend language compiling to LLVM IR using the LLVM c++ API (LLVM version 13), however I see some erratic behavior with segmentation faults when running the new ModulePassManager. Specifically I see the debugger halts execution in the llvm::EarlyCSEPass::run function call when a segmentation fault occurs. Can't see where exactly the seg fault happens inside this function as I am not currently using a debug build for the LLVM source code itself.</p><p style="margin-top:0px;margin-right:0px;margin-left:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,system-ui,"Segoe UI","Liberation Sans",sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(231,233,235);background-color:rgb(45,45,45)">I think the seg fault might have something to do with the way I set up my pass manager and run the pass manger on new instances of llvm::Module without any kind of reset to the pass analysis manager (not sure if this guess is correct though). I have highlighted my current code that sets up and runs the pass manager below. I would be grateful if you could give any insights into what I might be doing wrong and how it should be done correctly.</p><p style="margin-top:0px;margin-right:0px;margin-left:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,system-ui,"Segoe UI","Liberation Sans",sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(231,233,235);background-color:rgb(45,45,45)">Best, Sanket</p><pre style="margin-top:0px;padding:12px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:1.30769;font-size:13px;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto;border-radius:5px"><code style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit">
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">/* 
I have a "CodeGenerator" class object that holds the pass manager and the other related objects as public members
*/</span>

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">class</span> <span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">CodeGenerator</span> {</code></pre><pre style="margin-top:0px;padding:12px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:1.30769;font-size:13px;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto;border-radius:5px"><code style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit">public:
   llvm::PassBuilder passBuilder;
   llvm::LoopAnalysisManager loopAnalysisManager; 
   llvm::FunctionAnalysisManager functionAnalysisManager;
   llvm::CGSCCAnalysisManager cGSCCAnalysisManager;
   llvm::ModuleAnalysisManager moduleAnalysisManager;
   llvm::ModulePassManager modulePassManager;
   <span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">CodeGenerator</span>(); <span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// constructor for the class</span>
   <span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// other code that handles emitting the LLVM IR from the parsed AST of the front-end code</span>

   <span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// I keep the llvm::Module and llvm::Context instances to which the ir is emitted within this class as members</span>
   llvm::orc::ThreadSafeContext Ctx; 
   std::unique_ptr<llvm::Module> TheModule;

}

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">/*
I initialize the ModulePassManager in the class constructor
*/</span>
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">CodeGenerator</span>(): <span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">Ctx</span>(std::<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">make_unique</span><llvm::LLVMContext>()) {
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">public</span>:
  passBuilder.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">registerModuleAnalyses</span>(moduleAnalysisManager);
  passBuilder.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">registerCGSCCAnalyses</span>(cGSCCAnalysisManager);
  passBuilder.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">registerFunctionAnalyses</span>(functionAnalysisManager);
  passBuilder.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">registerLoopAnalyses</span>(loopAnalysisManager);
  passBuilder.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">crossRegisterProxies</span>(
     loopAnalysisManager, functionAnalysisManager, cGSCCAnalysisManager, 
     moduleAnalysisManager);
  modulePassManager =  passBuilder.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">buildPerModuleDefaultPipeline</span>(llvm::PassBuilder::OptimizationLevel::O0);
}

</code></pre><p style="margin-top:0px;margin-right:0px;margin-left:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,system-ui,"Segoe UI","Liberation Sans",sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(231,233,235);background-color:rgb(45,45,45)">After calling the constructor for the above class</p><p style="margin-top:0px;margin-right:0px;margin-left:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,system-ui,"Segoe UI","Liberation Sans",sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(231,233,235);background-color:rgb(45,45,45)">I initialize the Module to which the llvm ir is emitted.</p><pre style="margin-top:0px;padding:12px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:1.30769;font-size:13px;vertical-align:baseline;box-sizing:inherit;width:auto;max-height:600px;overflow:auto;border-radius:5px"><code style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit;background-color:transparent;white-space:inherit">CodeGenerator CG = <span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">CodeGenerator</span>();

CG.TheModule = std::<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">make_unique</span><llvm::Module>(<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">"module_name"</span>, *(CG.Ctx.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">getContext</span>()));

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// I parse my front end code and emit my llvm ir code to TheModule here</span>

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// then I call the ModulePassManager here to optimize the module</span>
CG.modulePassManager.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">run</span>(*CG.TheModule, CG.moduleAnalysisManager);
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// I move the optimized module to my JIT interpreter</span>
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">auto</span> TSM = llvm::orc::<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">ThreadSafeModule</span>(std::<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">move</span>(CG.TheModule),CG.Ctx);
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">ExitOnErr</span>(TheJIT-><span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">addModule</span>(std::<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">move</span>(TSM)));

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// Then, I create a new instance of llvm::Module to emit some other ir code</span>

CG.TheModule = std::<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">make_unique</span><llvm::Module>(ModuleName, *(CG.Ctx.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">getContext</span>()));

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// emit ir </span>

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// then call the optimizer again</span>
CG.modulePassManager.<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">run</span>(*CG.TheModule, CG.moduleAnalysisManager);

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// I repeat this several times changing TheModule to a new instance</span>
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// of llvm::Module to contain some new ir code and run the optimizer.</span>

<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// one of these calls to CG.modulePassManager.run ends up giving the segmentation fault </span>
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// there is no specific fixed instance of llvm::Module that this happens for</span>
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// The segmentation fault seems to happen at random for any one of the instances, on some runs there is no seg fault </span>
<span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;line-height:inherit;font-family:inherit;vertical-align:baseline;box-sizing:inherit">// The ir being emitted is also not changed on any of the runs</span>

</code></pre><p style="margin-top:0px;margin-right:0px;margin-left:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,system-ui,"Segoe UI","Liberation Sans",sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(231,233,235);background-color:rgb(45,45,45)">My suspicion is that CG.moduleAnalysisManager might need some kind of reset after I change the Module instance before I can run the ModulePassManager on the newly emitted ir. Or maybe I am missing something else in how the pass manager needs to be setup. Any help would be great.</p><p style="margin:0px;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;line-height:inherit;font-family:-apple-system,system-ui,"Segoe UI","Liberation Sans",sans-serif;font-size:15px;vertical-align:baseline;box-sizing:inherit;clear:both;color:rgb(231,233,235);background-color:rgb(45,45,45)">Thanks.</p></div>
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</blockquote></div>