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<p class="MsoNormal">That isn’t supposed to work; “x86-codegen” refers to the "X86 FP Stackifier" pass, which only makes sense on MIR, not LLVM IR. We could print a better error message, though: maybe we could add a report_fatal_error to the MachineModuleInfo
constructor.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-Eli<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>From:</b> llvm-dev <llvm-dev-bounces@lists.llvm.org> <b>On Behalf Of
</b>raghesh via llvm-dev<br>
<b>Sent:</b> Tuesday, September 10, 2019 8:31 PM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [EXT] [llvm-dev] Segmentation fault in opt with -x86-codegen<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi All,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">We are observing a segmentation fault in opt with -x86-codegen switch. This happens with any general llvm-IR. Please find attached a simple testcase. It can be reproduced with the following.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">opt -S -o a.out.ll a.ll -x86-codegen<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 traces of the error is as follows.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Stack dump:<br>
0. Program arguments: /home/raghesh/code/mirror/llvm-project/build/bin/opt -S -o a.out.ll a.ll -x86-codegen<br>
#0 0x00007ff5339d728a llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/home/raghesh/code/mirror/llvm-project/build/bin/../lib/libLLVM-10svn.so+0x76528a)<br>
#1 0x00007ff5339d4f64 llvm::sys::RunSignalHandlers() (/home/raghesh/code/mirror/llvm-project/build/bin/../lib/libLLVM-10svn.so+0x762f64)<br>
#2 0x00007ff5339d50a2 SignalHandler(int) (/home/raghesh/code/mirror/llvm-project/build/bin/../lib/libLLVM-10svn.so+0x7630a2)<br>
#3 0x00007ff53291ef20 (/lib/x86_64-linux-gnu/libc.so.6+0x3ef20)<br>
#4 0x00007ff533d86080 llvm::MachineModuleInfo::MachineModuleInfo(llvm::LLVMTargetMachine const*) (/home/raghesh/code/mirror/llvm-project/build/bin/../lib/libLLVM-10svn.so+0xb14080)<br>
#5 0x00007ff533d86178 llvm::Pass* llvm::callDefaultCtor<llvm::MachineModuleInfo>() (/home/raghesh/code/mirror/llvm-project/build/bin/../lib/libLLVM-10svn.so+0xb14178)<br>
#6 0x00007ff533b0c83d llvm::PMTopLevelManager::schedulePass(llvm::Pass*) (/home/raghesh/code/mirror/llvm-project/build/bin/../lib/libLLVM-10svn.so+0x89a83d)<br>
#7 0x00007ff533b0c9a3 llvm::PMTopLevelManager::schedulePass(llvm::Pass*) (/home/raghesh/code/mirror/llvm-project/build/bin/../lib/libLLVM-10svn.so+0x89a9a3)<br>
#8 0x0000557729456ac4 main (/home/raghesh/code/mirror/llvm-project/build/bin/opt+0x1dac4)<br>
#9 0x00007ff532901b97 __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0<br>
#10 0x000055772945795a _start (/home/raghesh/code/mirror/llvm-project/build/bin/opt+0x1e95a)<br>
Segmentation fault (core dumped)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">With a preliminary analysis, it can be seen that MachineModuleInfo pass which is a "Required" dependency of MachineFunction pass invoked by -x86-codegen.Here, the MachineModuleInfo is created through the call to llvm::callDefaultCtor<llvm::MachineModuleInfo>().
However, the default constructor of MachineModuleInfo expects a valid pointer to LLVMTargetMachine, which happens to be nullptr in this case and triggers seg fault when accessed.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">It would be great if someone could have a look at it and provide or suggest the proper fix.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Regards,<o:p></o:p></p>
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<p class="MsoNormal">------------------------------<o:p></o:p></p>
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<p class="MsoNormal">Raghesh Aloor<o:p></o:p></p>
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<p class="MsoNormal">Sr. Software Engineer<o:p></o:p></p>
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<p class="MsoNormal">AMD India Pvt. Ltd.<o:p></o:p></p>
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<p class="MsoNormal">Bengaluru.<o:p></o:p></p>
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<p class="MsoNormal">------------------------------<o:p></o:p></p>
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