<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/98477>98477</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang crashes on valid code at -O1 on x86_64-linux-gnu: Assertion `OldI != E && "Old is not a successor of this block"' failed
        </td>
    </tr>

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

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

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

<pre>
    It appears to be a recent regression as it doesn't reproduce with 18.1.0 and earlier.

Compiler Explorer: https://godbolt.org/z/nsfxrTq1j

```
[527] % clangtk -v
clang version 19.0.0git (https://github.com/llvm/llvm-project.git 7eae9bb856135136cddc4208a2b1546e9db44c9c)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /local/suz-local/software/local/clang-trunk/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
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Candidate multilib: .;@m64
Selected multilib: .;@m64
[528] % 
[528] % clangtk -O1 small.c
clang-19: /local/suz-local/software/clangbuild/llvm-project/llvm/lib/CodeGen/MachineBasicBlock.cpp:879: void llvm::MachineBasicBlock::replaceSuccessor(llvm::MachineBasicBlock*, llvm::MachineBasicBlock*): Assertion `OldI != E && "Old is not a successor of this block"' failed.
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: /local/suz-local/software/local/clang-trunk/bin/clang-19 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name small.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/local/suz-local/software/emitesting/bugs/20240710-clangtk-m64-O1-Wall-Wextra-pipe-fPIC-build-184127/delta -fcoverage-compilation-dir=/local/suz-local/software/emitesting/bugs/20240710-clangtk-m64-O1-Wall-Wextra-pipe-fPIC-build-184127/delta -resource-dir /local/suz-local/software/local/clang-trunk/lib/clang/19 -I /usr/local/include -I /local/suz-local/software/local/include -internal-isystem /local/suz-local/software/local/clang-trunk/lib/clang/19/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 -O1 -ferror-limit 19 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/small-f3a0d6.o -x c small.c
1.      <eof> parser at end of file
2.      Code generation
3.      Running pass 'Function Pass Manager' on module 'small.c'.
4.      Running pass 'Machine code sinking' on function '@main'
 #0 0x0000562a6845059f llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x419c59f)
 #1 0x0000562a6844dae4 SignalHandler(int) Signals.cpp:0:0
 #2 0x00007fed0cef0420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #3 0x00007fed0c92700b raise /build/glibc-LcI20x/glibc-2.31/signal/../sysdeps/unix/sysv/linux/raise.c:51:1
 #4 0x00007fed0c906859 abort /build/glibc-LcI20x/glibc-2.31/stdlib/abort.c:81:7
 #5 0x00007fed0c906729 get_sysdep_segment_value /build/glibc-LcI20x/glibc-2.31/intl/loadmsgcat.c:509:8
 #6 0x00007fed0c906729 _nl_load_domain /build/glibc-LcI20x/glibc-2.31/intl/loadmsgcat.c:970:34
 #7 0x00007fed0c917fd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #8 0x0000562a67710cb9 llvm::MachineBasicBlock::replaceSuccessor(llvm::MachineBasicBlock*, llvm::MachineBasicBlock*) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x345ccb9)
 #9 0x0000562a67717650 llvm::MachineBasicBlock::SplitCriticalEdge(llvm::MachineBasicBlock*, llvm::Pass&, std::vector<llvm::SparseBitVector<128u>, std::allocator<llvm::SparseBitVector<128u>>>*) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x3463650)
#10 0x0000562a6787317c (anonymous namespace)::MachineSinking::runOnMachineFunction(llvm::MachineFunction&) (.part.0) MachineSink.cpp:0:0
#11 0x0000562a677996e5 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#12 0x0000562a67da68fb llvm::FPPassManager::runOnFunction(llvm::Function&) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x3af28fb)
#13 0x0000562a67da6b49 llvm::FPPassManager::runOnModule(llvm::Module&) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x3af2b49)
#14 0x0000562a67da73f5 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x3af33f5)
#15 0x0000562a687088f8 (anonymous namespace)::EmitAssemblyHelper::EmitAssembly(clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>, clang::BackendConsumer*) BackendUtil.cpp:0:0
#16 0x0000562a68708e26 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>>, clang::BackendConsumer*) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x4454e26)
#17 0x0000562a68d7d66c clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x4ac966c)
#18 0x0000562a6ab708ec clang::ParseAST(clang::Sema&, bool, bool) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x68bc8ec)
#19 0x0000562a68d7da78 clang::CodeGenAction::ExecuteAction() (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x4ac9a78)
#20 0x0000562a69012da9 clang::FrontendAction::Execute() (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x4d5eda9)
#21 0x0000562a68f9554e clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x4ce154e)
#22 0x0000562a690fec46 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x4e4ac46)
#23 0x0000562a655a6ef5 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x12f2ef5)
#24 0x0000562a6559ff0a ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#25 0x0000562a655a38de clang_main(int, char**, llvm::ToolContext const&) (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x12ef8de)
#26 0x0000562a65496dfb main (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x11e2dfb)
#27 0x00007fed0c908083 __libc_start_main /build/glibc-LcI20x/glibc-2.31/csu/../csu/libc-start.c:342:3
#28 0x0000562a6559f99e _start (/local/suz-local/software/local/clang-trunk/bin/clang-19+0x12eb99e)
clangtk: error: unable to execute command: Aborted
clangtk: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 19.0.0git (https://github.com/llvm/llvm-project.git 7eae9bb856135136cddc4208a2b1546e9db44c9c)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /local/suz-local/software/local/clang-trunk/bin
Build config: +assertions
clangtk: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clangtk: note: diagnostic msg: /tmp/small-8058d2.c
clangtk: note: diagnostic msg: /tmp/small-8058d2.sh
clangtk: note: diagnostic msg: 

********************
[529] % 
[529] % cat small.c
int a, b, c, d, e, f;
volatile int g;
int main() {
  int h = 1, i, k;
  if (a) {
    i = 0;
  j:
    i = f;
    f = ~(-1 % (g % 3 / 2));
 k = g / h;
    if (c || b <= c) {
      b = h = ~(-1 % k);
 if (d)
        goto j;
    }
    while (h)
      b = ~f / i;
 }
  if (e)
    goto j;
  return 0;
}
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzsWktz27iy_jX0BgUVCb4XXsiSlbgqc-2KPWeWKhBoUhhTAA8AOs4szm-_BZB6UFYSJ2PfO4sz5VEkoB9fNxrdTYDUGNFIgMsgvQrS5QXt7Ubpy782ILmSjekvKsW_Xt5YRLsOqDbIKlQBokgDA2mRhkaDMUJJRA0SFnEFRgYkd1OdVrxngL4Iu0FRMYtmIaKSI6C6FaBnQbgMwvnwuVDbTrSg0fVz1yoNOojnaGNtZ4J4HpBVQFaN4pVq7UzpJiCrvwKykqZ-1g__jv48lhRk4fg3_EyvUpIH6RIFJEWspbKxjwg_DbP-N3oC7U2Iylk4CxthUUCKE-XCbvpqxtQ2IKu2fdr9gzut_gRmZ44rBwplVRVpFsVpFGeMc5aQsKCkitIkg5JXScJKFpByUP9AdQPWmfpcZOsswb18lOqLxK2Q_TNuZD_SbTRQjraKQ-uoO2XE8zB1I42lbQt8KbzPHC7FaBuQlen_wvvvqrZfqIajaW87trqXjwFZVUIOAq960XLElKxFMwi8osaAtkJJM5CsVC85YlRywakF9GGxQGLAQR3ZiKM32qkTlfMfYwFZjVYerCOrKHwHmdHbyxxX7B5aYBb4m-Bb7JFt-9YKxxXP0SyIr4Ik3GbJicrvEfkwL3Zhfm5sH_q3ETJb2rYzdrQHcFS-Lno8deVi5GQHHO0Lb_1CcfgAMiCr3yjbCAlX1Ah21Sr2OGNdF8TzIvc6n5TgyLPG8yCev6AehjV0LWVw3zMGxigdkOJ7PGQekMV3pToKr3--i24UZOFty29QQKIgXqJrFJAsIBkKCLltORIGSWURRWYHAqka2Y0wqBpEkoDkqKaiBT5mt7tP1_P7a2T6aisca9U3LjMqbV0q_bkcE5CVMKYHE5CVT6RCsrbngOwGENPUbFBF2aPVlIGzvvMp2CEFjozq9TDsOKkxignqokr3EhmmRWdHyPeWskfE-61bo2EonAVheadVo-kWUd30W5DW_N10sxuLSoQZixC2WnQtfDMXIgxbYbGq_kTYweNCI4oR5sLQqgVcawCEWQtUY2osrqBWGrDzCUiO8JYKiWvRApZ0C7tNgPBWgwPpQgD7FIs6wRDuBMMtPEGLyPBDGNwJQHhba7oF3CkhrStUS6kkIFxvqd1g0FoqhOu6w0xJtxY2iJdKIlxLhbXLSEI22NEivGVKGqt7ZpXGtBXUgEG47uUXITm2zioTxEuCsPWVArOud-7BWYKw7SX4gQYkaIeYQ9U3DWg3JWQTxMuGVwjXfhwzX2IHM7krFssfL55zOBjrhJFV1Tcu9EhIkjCPQjxmFLzNEnwb4T9o2-I_4NlqijvRAa7vbhbYpwocFUlE8oCsOLSWIlwz9QSaNvCPQqVh2CUOyC9H9pD9_JhL9SXCN0eFYWTZ7dxh7pV69kw-7iRtsTBfjYXtm2H9kZJvGPEd0h8WQrKazV5-nKF9qQ2e3Rf2UutIekbO97l_XoWvprgGrZXGrXA53q143cie4bGtDOJlMiMzR2ceRYcV15htgD1iIXGzrf1uaJXGXNBGKmMFc0mAcq6NaBBertcfFov1x_m_rtfLP-afV2S9WN2s5_e_BfEyQlg5VHbbuQV3KQ3XMQ15NlMIPyM2rfWRS-RBvABVB_E16qg2oBG1yCVIVSOXHQdK4ihdDR_Sy9Dj-JnYzXzupUsxqKPGoIDkq14yX0Pv3MBvVNIGtKuGSrq2tW_BUe2wkHysNck5WWOtRsxpN0I--o3uRdU7NQHJXftDXRnJB1koIHGIwucwDMM0IzQrkjRMy_qoCzBfzfDlTgtpfaF7GKrlUTOh6Ze1MlYD3fr67_o8G5DSPRS8TbkLyFX4nEQlS8t6_yzg4EdT-AmnkKB70UjafqSSt86lxYhmGDZjLxX6__eCyCgor4GHDOowISFarzUYqzSstd0Z4_fnmd3Wiqqz_qljZtQs9IijJCHhBG88UVOSPAwrpKkwbrVXuy6xaUXF8Cd2Q8Ln_U8yi93mN96K3bY3Xw2HzqXzXornYeDJo5G9--lFz1gQz9MoiOfRAUkyRRJmRVoiWilv6euQWD54w3N5JYVTchRd6amSnJSoAbsecK8NNK4xWj_Rtn-1B4S0rY8byremYXRQnbptOi8OurNzuteyXTvGNVduK_w9lWXugihODjrzqc4or3n2isBhLmQyHzJxXPNsEjLFcYjneRSyqvz_6v7feEfHScpYVU7MLU_MzbM0_LG5910r7EILKxhtr3kDP2mvS8Jj7jKWD2NP4LrMIF4cyO59_r8S9l-7uYgUfRBfTxhp67vjV_MOf-_j4CzO0kMKchlzkvHzIo-jnDm1VCr5dat6g1yzbzqf5cuJA-_H0jJEWC9v5TixK2bnvH6Yy0YDZx3V1qXIEh0JfpmXHdpoGg5lmUH6Mhx2OvwyHtCdhfUaPMfyzuMiE1ycZkVdHeFa3TnWXVX_aURvGQK0JkVdTUIgPgVfJeUrwP_m25LpGo9D7wS8SsoJ8OQEeB7Xx9HQQkPZ18OOHk242Xbt3oz_Q_hxXKcT-OmkW8nDoqiLH229662wc2NgW7VfP0Lb7VbkeDwgxfBI4meuhsf3-RhTR4mpl-LfPaw7O81Mrn_rvmhhYb3r4o6YONS0b-2aQwsWfsA4prIFeolnoaTpt64h84luHP3divb8DstOnQUkOxbrHDAKue1t19upF5aHZ4Nr2QgJY3o_IvkIlIO-B6rZ5rbzx7XIny-8JB3P5n5ANZxO_4DoE5XNOZKjSmG1kM1nqE9q8his8_P-Paz3geVGWt0b8QSfoV5Ie3ey8E_1mC1XooV7_8B2Wsv-SSHzxo8TSZoAySYbNJ_EHM95lrHv4RrCyD9oPGgqzXAs87sUJ8E4v39YKGnh2b5LrkkoK7OMTUyZtI20cvtnYsqd60bm9w9ToPewpWM8Vkq1h3_fGnJWVKyAKeTy1Ps0L85swjHQhyTwDKy3sIv94n18S_PiGCiZtFBlGBFOy2OgK-0We78lj5G-D0aeAqeTUkmmT8Z1maYJTJ053B_66zDJ4Lw_v23Uu8QxgyhNYGIHmfq6BpZMy8CA-GDO03gyPUX_wtx3SSmQUJZMUgqZ9FppSjOoU8RYtB6OYo6akbnW9KvL-vGCbajeFYf5Lj1OxsjCXwO9ixkRqQlMWxeSTM0o6zqkaOf7RfTgk8SRMfdb2rbDk87Qfp2x6aTsORljljwqjCXiWjyBPtskkPTEu3HBxyjf-dcf_gze886av07pW3sU6oJPA3vS36RJmfG6QuOhxJvqjoDw6QMAOTmnCIuwiNF63YqKrY2l2q5_5nSEmX53HjV89ZNejj8niRPiPg_qi9NgKktAg-K3d3xVlgfHj3cdQTxH_gjafeklrVpAViEY4hkxtd1Syf1dZ6W0Bf5t7uGFiHpMjjvW8U4T8d4LHg7tnG29AYSf_BgAEkfZqvzvCxa__oLF0cpI5VrOOTpcDqCtGfjGAPwbf0evzYwX1fOHh_niI3r4eI1Wt58-3f5x8z8f0Orm0_U9erj1w1e_f0Cfr-9uPz_sr4fvzl00F8Ylnm9eNu8JNCB_vgQcUbsX-ToPTO89ijAtOJm81vBrEszm55fhrRYjvUpJeeY9jv0Yo3Z6pyOkRdS3tr4yuA_uPvxlfx3EVwPZk3LtfOt2qUXNftj9GmuLLxT5OI483QYF8RJF_hLEfTzu-RAStX_YP-FCSHie8Ijyz_2yHubro3mEaj_2n4AUOBosJ0Xjv8RujRBxO5qUB55Hz9D4yc1E1ACLoSBfBPkCVSiIF46WvQCK_ORyNPJI-eNE1SCQH451x_8aZZUz7UhikC8PP75shL_1KjYnrIPW_9QevDgIOOIedMKE8YU-DbbX8sjTewH7d-Au-GXMy7ikF3AZ5STMwzjKs4vNZZ3xjEBZkaQsw4RRWteQQZXkdZ4TwviFuBxv1KMoDrMonEUJI5ATSlIeRhkrgiSELRXtzGXpmdLNhX855bIskjy_aGkFrfHvFRIyXjCTIF1e6Euf1f2tfRK2wlhzkGCFbeFyqBn-hRYwSEn0RFvBh-tAav2Vq5Loxd3Du73Kc9Hr9vLXX9UZHPJ0Sf43AAD__6XKsx8">