[llvm] [BranchFolding] Kill common hoisted debug instructions (PR #149999)
via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 28 17:50:33 PDT 2025
dyung wrote:
We are also seeing the same assertion failure when compiling the following code with `-O2 -g`:
```
typedef int a;
char b, d, e;
void f(int g) {
a c;
long h;
if (g < 0) {
c = g;
g >>= 6;
goto done;
}
if (g) {
g >>= 6;
h = 3;
goto done;
}
h = 4;
done:
e = g;
d = c;
if (h)
b;
if (h > 3)
b = 0;
}
```
Compile output with a compiler built from fbf6271c7da2:
```
$ ~/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang -c -O2 -g repro.c
repro.c:21:5: warning: expression result unused [-Wunused-value]
21 | b;
| ^
clang: /home/dyung/src/upstream/llvm-project-build/llvm/include/llvm/CodeGen/MachineInstr.h:2004: void llvm::MachineInstr::setDebugValueUndef(): Assertion `isDebugValue() && "Must be a debug value instruction."' 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: /home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang -c -O2 -g repro.c
1. <eof> parser at end of file
2. Code generation
3. Running pass 'Function Pass Manager' on module 'repro.c'.
4. Running pass 'Control Flow Optimizer' on function '@f'
#0 0x00005fcdd1d0fc12 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2216c12)
#1 0x00005fcdd1d0c90f llvm::sys::RunSignalHandlers() (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x221390f)
#2 0x00005fcdd1c4a818 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
#3 0x0000768587845330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
#4 0x000076858789eb2c __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#5 0x000076858789eb2c __pthread_kill_internal ./nptl/pthread_kill.c:78:10
#6 0x000076858789eb2c pthread_kill ./nptl/pthread_kill.c:89:10
#7 0x000076858784527e raise ./signal/../sysdeps/posix/raise.c:27:6
#8 0x00007685878288ff abort ./stdlib/abort.c:81:7
#9 0x000076858782881b _nl_load_domain ./intl/loadmsgcat.c:1177:9
#10 0x000076858783b517 (/lib/x86_64-linux-gnu/libc.so.6+0x3b517)
#11 0x00005fcdd0ed7d3f llvm::BranchFolder::HoistCommonCodeInSuccs(llvm::MachineBasicBlock*)::'lambda'(llvm::MachineInstrBundleIterator<llvm::MachineInstr, false>)::operator()(llvm::MachineInstrBundleIterator<llvm::MachineInstr, false>) const BranchFolding.cpp:0:0
#12 0x00005fcdd0ee0e05 llvm::BranchFolder::HoistCommonCodeInSuccs(llvm::MachineBasicBlock*) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x13e7e05)
#13 0x00005fcdd0ee27d9 llvm::BranchFolder::HoistCommonCode(llvm::MachineFunction&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x13e97d9)
#14 0x00005fcdd0ee2b3b llvm::BranchFolder::OptimizeFunction(llvm::MachineFunction&, llvm::TargetInstrInfo const*, llvm::TargetRegisterInfo const*, llvm::MachineLoopInfo*, bool) (.part.0) BranchFolding.cpp:0:0
#15 0x00005fcdd0ee32d3 (anonymous namespace)::BranchFolderLegacy::runOnMachineFunction(llvm::MachineFunction&) (.part.0) BranchFolding.cpp:0:0
#16 0x00005fcdd1072db3 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#17 0x00005fcdd1737341 llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x1c3e341)
#18 0x00005fcdd1737791 llvm::FPPassManager::runOnModule(llvm::Module&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x1c3e791)
#19 0x00005fcdd17380e4 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x1c3f0e4)
#20 0x00005fcdd1fa246c (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
#21 0x00005fcdd1fa313c clang::emitBackendOutput(clang::CompilerInstance&, clang::CodeGenOptions&, 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>>, cla
ng::BackendConsumer*) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x24aa13c)
#22 0x00005fcdd269c06e clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2ba306e)
#23 0x00005fcdd424706c clang::ParseAST(clang::Sema&, bool, bool) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x474e06c)
#24 0x00005fcdd29d9d17 clang::FrontendAction::Execute() (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2ee0d17)
#25 0x00005fcdd295ae8d clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2e61e8d)
#26 0x00005fcdd2acb47b clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2fd247b)
#27 0x00005fcdd07306ad cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0xc376ad)
#28 0x00005fcdd0725f17 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#29 0x00005fcdd27099cd 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 0x00005fcdd1c4acde llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2151cde)
#31 0x00005fcdd270aac8 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 0x00005fcdd26c807a clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2bcf07a)
#33 0x00005fcdd26c91e2 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2bd01e2)
#34 0x00005fcdd26d5f04 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0x2bdcf04)
#35 0x00005fcdd072b6ee clang_main(int, char**, llvm::ToolContext const&) (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0xc326ee)
#36 0x00005fcdd0627b2a main (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0xb2eb2a)
#37 0x000076858782a1ca __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#38 0x000076858782a28b call_init ./csu/../csu/libc-start.c:128:20
#39 0x000076858782a28b __libc_start_main ./csu/../csu/libc-start.c:347:5
#40 0x00005fcdd0725495 _start (/home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin/clang+0xc2c495)
clang: error: clang frontend command failed with exit code 134 (use -v to see invocation)
clang version 22.0.0 (https://github.com/llvm/llvm-project.git fbf6271c7da20356d7b34583b3711b4126ca1dbb)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/dyung/src/upstream/fbf6271c7da20356d7b34583b3711b4126ca1dbb-linux/bin
Build config: +assertions
```
https://github.com/llvm/llvm-project/pull/149999
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