<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/69217>69217</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang: fatal error: error in backend: register rbp is allocatable: function has no frame pointer
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

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

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

<pre>
    Compiler explorer: https://godbolt.org/z/9Yq36Wdov.

The following program `small.c` triggers a crash in clang-18:

``` sh
% cat small.c
register long a asm("rbp");
long foo() {
  return a * a;
}

% clang -O1 small.c
fatal error: error in backend: register rbp is allocatable: function has no frame pointer
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-assertions-trunk/bin/clang -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -S --gcc-toolchain=/opt/compiler-explorer/gcc-9.2.0 -fcolor-diagnostics -fno-crash-diagnostics -O1 <source>
1.  <eof> parser at end of file
2. Code generation
3.  Running pass 'Function Pass Manager' on module '<source>'.
4.  Running pass 'X86 DAG->DAG Instruction Selection' on function '@foo'
 #0 0x000000000372f498 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x372f498)
 #1 0x000000000372d15c llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x372d15c)
 #2 0x0000000003675fe6 llvm::CrashRecoveryContext::HandleExit(int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3675fe6)
 #3 0x00000000037244ae llvm::sys::Process::Exit(int, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x37244ae)
 #4 0x0000000000bed7da LLVMErrorHandler(void*, char const*, bool) cc1_main.cpp:0:0
 #5 0x0000000003680983 llvm::report_fatal_error(llvm::Twine const&, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3680983)
 #6 0x00000000023a9aaf llvm::X86TargetLowering::getRegisterByName(char const*, llvm::LLT, llvm::MachineFunction const&) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x23a9aaf)
 #7 0x000000000482a9de llvm::SelectionDAGISel::Select_READ_REGISTER(llvm::SDNode*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x482a9de)
 #8 0x000000000482dd33 llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x482dd33)
 #9 0x0000000002318899 (anonymous namespace)::X86DAGToDAGISel::Select(llvm::SDNode*) X86ISelDAGToDAG.cpp:0:0
#10 0x0000000004828c5f llvm::SelectionDAGISel::DoInstructionSelection() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4828c5f)
#11 0x0000000004836097 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4836097)
#12 0x0000000004839618 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x4839618)
#13 0x000000000483b312 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (.part.0) SelectionDAGISel.cpp:0:0
#14 0x000000000232257c (anonymous namespace)::X86DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) X86ISelDAGToDAG.cpp:0:0
#15 0x0000000002b04411 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#16 0x00000000030b2af9 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x30b2af9)
#17 0x00000000030b2d31 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x30b2d31)
#18 0x00000000030b3552 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x30b3552)
#19 0x00000000039a3c02 (anonymous namespace)::EmitAssemblyHelper::EmitAssembly(clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>) BackendUtil.cpp:0:0
#20 0x00000000039a40a9 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x39a40a9)
#21 0x000000000499c34f clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x499c34f)
#22 0x0000000005ea1529 clang::ParseAST(clang::Sema&, bool, bool) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x5ea1529)
#23 0x000000000499b538 clang::CodeGenAction::ExecuteAction() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x499b538)
#24 0x00000000041fefa9 clang::FrontendAction::Execute() (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x41fefa9)
#25 0x000000000418044e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x418044e)
#26 0x00000000042de12e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x42de12e)
#27 0x0000000000befa56 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbefa56)
#28 0x0000000000be731a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#29 0x0000000003fdc649 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
#30 0x0000000003675f24 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3675f24)
#31 0x0000000003fdcc3f 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
#32 0x0000000003fa4e05 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fa4e05)
#33 0x0000000003fa586d clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fa586d)
#34 0x0000000003fad795 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0x3fad795)
#35 0x0000000000becefc clang_main(int, char**, llvm::ToolContext const&) (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbecefc)
#36 0x0000000000ae7091 main (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xae7091)
#37 0x00007ff94969a083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#38 0x0000000000be6dfe _start (/opt/compiler-explorer/clang-assertions-trunk/bin/clang+0xbe6dfe)
clang: error: clang frontend command failed with exit code 70 (use -v to see invocation)
```

Clang version:

```
clang version 18.0.0 (https://github.com/llvm/llvm-project.git ab737a86993bc7bf92cbb9d51f47f8825a717333)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/compiler-explorer/clang-assertions-trunk/bin
Compiler returned: 0
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkWktz47aT_zT0BSUVCVJ8HHyQJcuZlCfjspxs9qQCwSaFHRBgANCP_fRbICmZoOXYSTTZwz-VmaEAEPj1rxv9AEG0ZpUAuPQWV95ifUFas5fqkkohKs7ZRS6Ll8uVrBvGQSF4brhUoLxwifbGNNoLlx7eeHhTySKX3Mylqjy8-V8Pb7L__iOM_6uQj3PPX3v-sv_7YQ-olJzLJyYq1ChZKVIjL_Z1TTifUy_2kVGsqkBpRBBVRO8RE4hyIqpZkNoFR9N5sd__j_R-aMELRIlBh_m6RgUV0wYU4lJUiCCiaw-nHsYqbzyMPZx54VU_tBtRStn1Z8hLhnaEFJhWCUSQh5eIHF_wkrWDyK5vwaLZt8BFURJDOAKlZEdg92Blywn9DqKwbUegKm8Q04hwLikxJOdgu8tWUMOkQHuikZCoVKQG1EgmDKh-kbvb6-X2Guk2r5lBBOVthRQ0Uhlk5FRpzOzbfE5l7eEN54-Hf2aNkv8D1Hh4w7RuQXt4g4goEBOUtwUgs4dBNRa7UYSCh1eoUdAoSUFrKJCWreqb7ZtEa0kZMVAg1QqkqWKNGSxjawj9joq2bo7a9ecI3Q3GQVTV1iCMxY08vJGNBUYHm5wdbRJveiMhWoOyLOmZUa347uFNzsShG82q4omochahWYVm0s5ImsbO25qmNXONZrUlAc1mz2k8I7qe6RdhyLMXri3PHM22aDarKJ0ZKTndEya8cP2nwOzgbI7nPpqVVHKpZgUjlZDaMKrRrBRy1tHpNn8LkBeuBh7D656ZYI5sK8jSC69RQ5QGhYhBIAokS1QyDv1APEcrWQCqQIAilo--PZwjdN8K0e0_ojXycLI52NWdbfhKBKks7gRJgWpZtBzsKAcMTgbtRSfm-z2N0Xp5M_PC6_XyBn0R2qi2X2ELHLqnYfqjSdsFIr_becmw5Twc-sh_9g__hQkuoyxFnamGSy9c6hfdP9wpJkxnSA-9NaavgxR52kltFJDaw7G1SCZMt7ntHv-H9uThK_95AGb9yBF5MEFeBAt6CvmKAxFt801sWSUI93Dais4nF523OjdOC8PBiR2ccbIoIR7hXFm7vAcqH0G9rKQw8Gz6np-IKDhcPzPj4fTsjPZAHKThhNEoInDaFjof1P8Y41uhXEp-bkYtDAdnNMbp51AkBUG3t799vbYev6dNeTh9lKzw8NLionuiEJVCm6HhAJTSYFcTJua0sd7R7_4cV1q4ukv9LA1HjPR-f9fFnV0fd8b74uGJCTisGv8YenpMDj3xGDQOSUZIOQL9exo_EFWBuZVPoJio-uYKzP0QHK9efiG13eJvWHud5fb2wW34SuieCTh6ulexs_75fEIPMjlCJ2OhoxSTrBjb7tErrpc3X7bAx627--vlend_ffNl-3B972hwu_5FFtAJf0alDfAc_OkEf1GE4Sfx2yi0knVtXf5p7Ct0dHlvVHrsObeHGYRwpMxc0wzSNOtWJEKKl1q2GglSg266CJMd7XW9vHmQJyR_X1e_p7EdfHjx7e62AcSfcJ7SRfkh52s5irajYJuemzyL5kiehRu4cMPYz5IP4VrjuAGxFMV1zcx6eXN-pB0QBymeIM3iIP2kMS85vyKa0Ssu6XftKPikazmnHBamI0c4kSO3on0kh2rFNzHxho4cb_oOgswboszct7-mU5824MjdThgvEvq3ttPfxPypXebEUJz7URQE78cNmyCPMJ0E86fMnZjvNC4nTIZ-jkmZjXBt7uyrh1T9LyM6U3jvYTlGmUxxF2HwCdxfuzLDVerQdH7MRRg4mNMJ5nCxGG8kDhWhL0Ny-Yr-S9282ue_g9wCc5A7ESvMSEh9_NEWs552qTXUOX_5CXhz0MO43WZX3cJdz1V_QrEcjGiFtCn6nlawP1rYNUZ54cotuZonxQzsDoXX6KUCStJysyuAg4EPXgyvu3IzQwOIXw077W6wP-Ei8kmGRlJY-YZJvnW1vivk-rX2vhYVEzAkxaMhPwEpQG2BKLr_1nTacvLn0dAhsH0wqs90Pxh0S0R1asjI0xubKN9DOcl5BzNcTiZ8o87XV74Io1rNHuEeypUwdxO9PpaD99swDtsXbaBT0P-TRZxvZ_XGMt5Z2E1nsoyGUXmCxJUUuq0PW6gv7h4UEZp3Zy6_CjYxs-X24VBGnztF6EE6UjipzgJIsMDOnrgjSsNy--Bi3EJNnJLwB5SGAxgHbTjhPF-E6YlNNRjuUN8DbQ0sf0ya20NwMDpJTRSUULpeZqOsdo-7awzy7PD61R14Cxde6kcRuBT2C9oqgQgKp1l8X55z22yP0BHByXwiXECAHREGsK-SPEpK3gJ_I-m5y-QemQM9mRz9lGQRH89wnBRhqRR5sR47XLk1b-9O39TBx8OiM0rQ43MESCcCJGFA0IHwVfDQeYFxVVsTzn8DauSQDp2QZhKs7ByDB3RKpUKxR1CnQ7ub5pQFjaOso2Q07-Ekeac6Vrvefsd1EcMOoYTznNDvu1JYpK-20q892M0qWMm6JqKYbt6T2jvGMNmFaMKd6PUamYeoNQp6ux19fg6C_kduq0ob4boTr45FZ7Bt2BlFmNGH7sl0w7ciqUb9dsjoPHF5PO3qX_FwwkmdF8TDyStVOD0cPP8s85P6mBzLx8mixNGnDo3vW7ElJXQJ5mdVd_ZzZRyNbX5yUl8WlIZOpP-PM45JyfquFbifDkoSgb94l7hOa-RNTDyw6bjuyYt2wHvJ8Z8MXU5Otc98zDsI7JhSOGFkkcbFX2XkZ5nr9-n4Wea3TJv3CoE37vhoAQ1hVvnDh5DPMjiYyQ_m0dLk8BhNeCyS7F3LWo-endTgRE7wHv__Io_ndGY9MQ5zi0kAp1DSHuUhBzkg75zI8s2Xk_fC8xmzDovJAe1kfD6BxM8CZOGeb9V-UmfVQ7KWlGUWZXFG_DREux1nufW1RJndCAJnuYc3z2m8i6MZZ6J9nlWi7TvoXMt53H_7ifzR5y67yjSjiosSUD__OTm10x7XPVjl62WT_u5DOeTyiA72WRLGoUBPzOwRPDOr8QJQ4ltkrQY0e0RGIg2A2CjLziaXb8b3X1bdQo-g9ODXTt3WGaE8DEVBOvfn3cJ_7ZLKvGIGkTwJE5LGWRbmNMnLDNM8z4pFUEZJmaZ4QZIgCUdfe_qDF8vMoNJWfBfySYxUO9xXUkAKVMuiO4tGjdTsue_q6grOoVgz9c-upvTEHS5Z9feMoLsP5E-IuyguwyILM3IBl0GcJVGcBGlwsb9Mo7SMMprhIA6KiKZFmvhJFGV5kNEkX8AFu8Q-DgM_iIMozMJsHgSLktAyjxdlmubpwot8qAnjc0vuXKrqorv7cxlnOEguOMmB6-6WGMaD3WFvsb5Ql50y8rbSXuRzpo1-ncEww-HyaI0_-ALURav45d-_4dQJ-n8BAAD__3TzEcM">