<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/125626>125626</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            crash when compiling with emit-cir and fsanitize=undefined
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          midnightveil
      </td>
    </tr>
</table>

<pre>
    https://godbolt.org/z/azdrjn3Wf

```
clang version 20.0.0git (https://github.com/llvm/clangir.git c4e58420474090601b9419159ad3343ffb530c34)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-clangir-trunk-20250201/bin
Build config: +assertions
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
 (in-process)
 "/opt/compiler-explorer/clang-clangir-trunk-20250201/bin/clang-20" -cc1 -triple x86_64-unknown-linux-gnu -S -disable-free -clear-ast-before-backend -main-file-name example.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -fno-verbose-asm -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debug-info-kind=constructor -dwarf-version=4 -debugger-tuning=gdb -fdebug-compilation-dir=/app -v -fcoverage-compilation-dir=/app -resource-dir /opt/compiler-explorer/clang-clangir-trunk-20250201/lib/clang/20 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/x86_64-linux-gnu/c++/11 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/backward -internal-isystem /opt/compiler-explorer/clang-clangir-trunk-20250201/lib/clang/20/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdeprecated-macro -ferror-limit 19 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -fcolor-diagnostics -fclangir -emit-cir -mllvm --x86-asm-syntax=intel -fsanitize=alignment,array-bounds,bool,builtin,enum,float-cast-overflow,function,integer-divide-by-zero,nonnull-attribute,null,pointer-overflow,return,returns-nonnull-attribute,shift-base,shift-exponent,signed-integer-overflow,unreachable,vla-bound,vptr -fsanitize-recover=alignment,array-bounds,bool,builtin,enum,float-cast-overflow,function,integer-divide-by-zero,nonnull-attribute,null,pointer-overflow,returns-nonnull-attribute,shift-base,shift-exponent,signed-integer-overflow,vla-bound,vptr -fsanitize-merge=alignment,array-bounds,bool,builtin,enum,float-cast-overflow,function,integer-divide-by-zero,nonnull-attribute,null,pointer-overflow,return,returns-nonnull-attribute,shift-base,shift-exponent,signed-integer-overflow,unreachable,vla-bound,vptr -fno-sanitize-memory-param-retval -fno-sanitize-address-use-odr-indicator -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /app/output.s -x c++ <source>
clang -cc1 version 20.0.0git based upon LLVM 20.0.0git default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include"
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11
 /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/x86_64-linux-gnu/c++/11
 /usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/backward
 /opt/compiler-explorer/clang-clangir-trunk-20250201/lib/clang/20/include
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
NYI
UNREACHABLE executed at /root/llvm-project/clang/lib/CIR/CodeGen/CIRGenFunction.cpp:1170!
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /opt/compiler-explorer/clang-clangir-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -fno-verbose-asm -S -Xclang -fclangir -fcolor-diagnostics -fno-crash-diagnostics -Xclang -emit-cir -v -fsanitize=undefined <source>
1.      <eof> parser at end of file
2.      <source>:2:5: LLVM IR generation of declaration 'main'
 #0 0x0000000002e67b9b llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x2e67b9b)
 #1 0x0000000002e65104 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x2e65104)
 #2 0x0000000002dac710 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #3 0x000077f9a3242520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x000077f9a32969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x000077f9a3242476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x000077f9a32287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x0000000002db857a (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x2db857a)
 #8 0x000000000474e500 clang::CIRGen::CIRGenFunction::StartFunction(clang::GlobalDecl, clang::QualType, cir::FuncOp, clang::CIRGen::CIRGenFunctionInfo const&, clang::CIRGen::FunctionArgList const&, clang::SourceLocation, clang::SourceLocation) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x474e500)
 #9 0x0000000004751618 clang::CIRGen::CIRGenFunction::generateCode(clang::GlobalDecl, cir::FuncOp, clang::CIRGen::CIRGenFunctionInfo const&) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x4751618)
#10 0x0000000004683d18 clang::CIRGen::CIRGenModule::emitGlobalFunctionDefinition(clang::GlobalDecl, mlir::Operation*) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x4683d18)
#11 0x0000000004688027 clang::CIRGen::CIRGenModule::emitGlobal(clang::GlobalDecl) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x4688027)
#12 0x0000000004688547 clang::CIRGen::CIRGenModule::emitTopLevelDecl(clang::Decl*) (.part.0) CIRGenModule.cpp:0:0
#13 0x0000000004668083 cir::CIRGenerator::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x4668083)
#14 0x00000000045017ac cir::CIRGenConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x45017ac)
#15 0x0000000006955694 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x6955694)
#16 0x0000000003b2e9d3 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x3b2e9d3)
#17 0x0000000003aab326 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x3aab326)
#18 0x0000000003c15c4e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x3c15c4e)
#19 0x0000000001116d64 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x1116d64)
#20 0x000000000110dbe0 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#21 0x0000000003860799 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#22 0x0000000002dacb72 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x2dacb72)
#23 0x0000000003862b4e clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (.part.0) Job.cpp:0:0
#24 0x000000000381d47b clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x381d47b)
#25 0x000000000381e4ef clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x381e4ef)
#26 0x000000000382a914 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x382a914)
#27 0x0000000001112ea2 clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x1112ea2)
#28 0x00000000010026b3 main (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x10026b3)
#29 0x000077f9a3229d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#30 0x000077f9a3229e40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#31 0x000000000110d205 _start (/opt/compiler-explorer/clang-clangir-trunk/bin/clang+++0x110d205)
clang++: error: clang frontend command failed with exit code 134 (use -v to see invocation)
Compiler returned: 134
```
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzseltz27iS_6eBX1BQkSB1e_ADI1mZTGXOzD_Of87ukwoEmxSOQYAFgLI8n34LIGWSiu2MZ5RTu7WbcmwKbDR-fUFfADFrRaUAbtH8A5pvb1jrDtrc1qJQojq4Iwh5k-vi6fbgXGNRkiG6Q3RX6SLX0s20qRDd_YHojv1RmH-p5J8lijL_s4j6nyjjkqkKH8FYoRWm0SyaRZVwGNHVBVfhDm0-47pGdCfl0f8Jk4WZ-Qk8hfkqpVG6TKN1tIjifJ3G63i-ZkWSpElZ5vMk4kmK6BpF2VdmKnAoyfBptdgvUtKqB6UfFZFCtSdSqdYTHQywAte6AOlJG23FCUXZJ2UdkxKKrTB-HNGdbpzHo-tGSDAETo3UBswZI-mREmda9UBoROcRjWJEd7lQKMo-tEIWmGtViqrj-IFZC8YJrSyKsp1uVYE5U4UomAP8cbPBokPBPE2PorV-RSlyry_OEd310g1S0V0cXZthjKLsHiRwB8Xf57R5BlW30gk_JcnwDCUfUBrVi_RVkoT2NAl9leb0THQKVM-wX13Le6JQpDGag7Wd92BE6d81-pmIRohSTDiPMXFGNBJedUlM7jEphGW5BFIaAEy4BGYIs47kUGoDJGf8AVSBSc2EIqWQQBSrAcOJ1Y2EGW8aTGoDUvNgHhK8GzeCY9IITiQcQWLafRCWNAIwqUvDaiCNFsqBQcmWSYlJWTN3IGCM0piUZUO4Vs4w7lCy1QqTUmlivJ8JVRFP2w0dweTaAmG2xqTmWllnWu60IUwKZsFiUrbqUaiCOC-pRcmWYuLCjiW8ab1-yCLFxLUKwkAFCoyXoIC8rYhQpSYPQhUo2Y74Y1I8MlOSPtigZJv2MyownplQFUq2VZFjUnacOtt2iir8Zt_6aOZVeMSk5PoIhlXwBpkBq1vDwQ__rTjR7ZzwGtEdjTAJtlBMEmGfrIP6PbuM7mazb38JxWVbgF8H0Q_hZxfHP3alF2b9-xYfr-S3JeMPj8wULy96NdMNEN6UTnMm_yTpX1TEC7TfrgYn_8C_XfV1G749-_1LhO3YGODMQUFqxo0POGCMNkSKWjgcrzEpK9Xy8eae0VmMSWkfREN0YQg_AH8gQpGqLv3uPZ0InDg0Icl6huMPXEttSCFYpbR1goexzsKYQC0c4f6p9pUIJsSHJGZrYp-UYyeUbL1wPkZapoQTf0AImqJSNSiH6IYZw55I7qOjRXSTay39n1ZI53PDBlRbI7oppWaOcB_ffawppX70o63iIbXSjV_GR69CHEUBJH8if4DRiG6UVqqVkjDnjMhbB36slX6VPoyPORpwrVHPD5a8NN0eROlIzuzwAU6NVp1EoVQsyBnQiHmrDDB-8LEc0c1Rsk5u_9w4M9IRMRBC6v8EXV1XRW8ppQZT_Z_7vOE-SpORsmptnkjDDKuJAXdk8oKCFYUBa0lrIUQFoQrBWSgPSv_OigqT7X7_cbPZ_5T9frff_jP7sqP7ze7TPrv_BSXbGBONuwTv00LrmtbNLCYn3OcTjJJNl_ZRcvfc44QS79tGxyukwG2jFf78-fdfRm8KKFkrHe4qn7caFVEpbYSqsNIKTsI6UA4XwoAve576avVH5QrP_U9CmMxANDnHd0TpzK9CsQVm-AFbx4yz-AAGfAM4JU42nji5e5X4h5UI12X9ndLnRwoy1Dr9Kj-guJnin1Yzk3dvaOQlsii7UwXW5dn8Ulg3Q1H2j__8hKLs___jy122-Sn78PkOwwl465s75jwbo7Xrzw58O_cv4G4EvRNk8-mL_60L-Aiq-_wR1K6PmL57QkkWx8sIUW-g3z7fZfd32La5r0IYztsKG2i0cdhp_P0DjAsswtoWLKI7zFSBzw7vDoC5YfaAvdF8h-UDIW4M9E0pFLgPN3QTZjJrNRe-WsKmVdhyI5qgo3vH-AMu2rrpdko0Q9H6N6Mrw2rMTNX6_GL_ypnGtKvt4yCpuo4rxaR6JWh-t4C67BjvMfmPPqAOBdmL5ZrSJKhtOnyePNRwx2mZ1qoCSqGguAzjsVcWSjagSx99GmYsGO9b0Pmjb7ZRlNGebJiaZBQl2dyrNYT4T1-6jjU0jH5mAVyy_iOiS9-6I7rsvD-JcHSKzv8oLJb5OsfBf5IMJZl9st3Db0YoFwz8tXOR1UBk2ONeW2eA1YguvJsIn3XXGNHVNSyN6Ifo1GN7PiJJ4gvk8zhKX0K-kcBU2_yq7kWlfJhYtaqrB7DUfomr4_RIBpx0grNgfBlHeONd50tXkD51wH5iqpB-uVWvvQnNRisHJ9fHiCj87_gnPf_lslyzhKZ0TqNeoi7qvBDRpcj5zOrZIkAOUwbA6ZTherEuOW5cOK7cPwgp38c9zB-4zy_hpssFrmxQwXthp8vFwHgxZUxXyzLBLPfR8l1sw8SB7XJqvnw1X7LrOkzHc1hxNV4xXaYwjyLczeocOmSN8fM5g3Rj975ieR6iq9HUj1LnTG6B-1J7zPP_tUx-fWpCjOfh3Bklmefxa3NB-frqn1SpcTgR66PAK7PO9JmpPgvrXptyHyLc5_4k8Tsvr7uHe6UPJllPTTKPF_HqPSbpAzL41P-mRa6j-mtrI8jbacMH3knOSBerpPieNn7RRSuhG_GpsZP6jH7rM6L4nrfW8qycX5s-uyGaXV3YTpxB2PhC2FVEl39F2NdFu7oAHuIgAL0UYJ6-U4CvuvkMR-jhjsXoRs5GmDXMuFkUcteI0UXO8piSKabFKlolg_N3k72NdT_S5ca3cXw0um2-QHl9hQZ4g0LTCfh5FC8ZvwS_0cq2Nfx3gN8BHODPx_AX6_l8sU7H_vCbrzyz-69TiPdQsz5G9-dB_d_rou3xDGgXY7RJTmFdJGO0O-MLI1Vko2h713VmAdd14fUABniT6iBhLE_oYrK5-gXDpa7iMAGYvZChL-S5fjTvQQ4iTMqNhMdznsJYhB7sIMnxOeuu3pL0-rG5BzdAn6TlOI4XxSLFnMf7rscZtSiZMezJ765kww_MnHNl5hson2QnY3SDj1oUP0CCHuOzBDSaShAVOUT4rPFN_DVssZEc9zWT8vdw7PWpbuSL4oRNOkzxPPruYVIiFEYcwXwbnOkk4yWrRbRcr4NCRkzPp7x7E3Qa3nb7rWtJUZJxJmXO-MO-VB7m4Cndwr3XbOKNrmumisut-6LtrOvpdLhKYV4BI-U4I1QVKO96wz5P2O_56RTH3YecWcH3NpD3KpwQ-4G9M0w4e359wY7JcMXt89Pze0-SDYExOE-n8DAF0aVkdV4w33w_q4quzk3ozzp_wRjfdI_5ko7s8FKP2L350qp7VoJ8mujybbtduxXu4A7enlx4Fs2noeZ_nWdcVE0vu0A61VpcpMv8Va0N3xW4jN5BlZOQfTHRE7zWjL1Bmk3KgpFg14v7ncyDH80vNAIplO_VyM86t6-r42edf9ObvhWFn83fMF8IbsIRzp_XYO8jP16PXlODHqfF1YqydZy-hnk7ep6UBC_UAq_p_9-oxytXHp1uBs0tLyoPCox2KM-1xxl5iCBZv_-_n5WvXG14XAPqSakXRxFd5An2eK-7bMd4WHZ9cTK3LtbvPKEMU54ZPh9aPzOENML7vZ-zD_d1-5FQf3oJSEdLxJeFGY3muGN-ZRsF1t3C45dJhsN3UPxDd6lQ9q0B5r3bl0xIKPCjcAcMJ-EdqQAcJ6lH2FrA5IidxhYAi1HV7lc6V-u4u1MHv-v8zPH3Z2-K26RYJ2t2A7fxMlkt0iSmi5vD7YqlRZ5ESZSXZTnPy3jBV3ESwWo1TxIWLW_EbX-Hl0YpndPFLOJ8HbEyT5Y05oxylEZQMyFnfkPMtKluwuXUbUznC7q4kSwHacMXgylV8IjDW0Qpmm9vzG2418rbyqI0ksI6O7Bxwkm47e6zHg-gcGcfoapeTed7maC_l-5lblojL79y_I67tV6C4y39rwAAAP__IuUTZA">