musttail crash on armv7 iOS > 5

[Un1q32]

https://godbolt.org/z/GrK1oYrcW

[llvmbot]

@llvm/issue-subscribers-backend-arm

Author: None (Un1q32)

used test case from #63214

void name(int *params, int *program, int r, int g, int b, int a) {
  auto fn = (void (*)(int *, int *, int, int, int, int))1;
  [[clang::musttail]] return fn(params, program, r, g, b, a);
}

compile with:

clang++ -target armv7-apple-darwin test.cpp -c # crashes with all 32 bit arm architectures except armv4t and armv5

output:

fatal error: error in backend: failed to perform tail call elimination on a call site marked musttail
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: clang++ -target armv7-apple-darwin test.cpp -c
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module 'test.cpp'.
4.	Running pass 'ARM Instruction Selection' on function '@<!-- -->_Z4namePiS_iiii'
 #<!-- -->0 0x0000000005dd91f8 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/opt/llvm19/bin/clang-19+0x5dd91f8)
 #<!-- -->1 0x0000000005dd6fee llvm::sys::RunSignalHandlers() (/opt/llvm19/bin/clang-19+0x5dd6fee)
 #<!-- -->2 0x0000000005d4d59e (/opt/llvm19/bin/clang-19+0x5d4d59e)
 #<!-- -->3 0x0000000005d4d55b (/opt/llvm19/bin/clang-19+0x5d4d55b)
 #<!-- -->4 0x0000000005dd39d7 llvm::sys::Process::Exit(int, bool) (/opt/llvm19/bin/clang-19+0x5dd39d7)
 #<!-- -->5 0x0000000003db0ac3 (/opt/llvm19/bin/clang-19+0x3db0ac3)
 #<!-- -->6 0x0000000005d537d9 llvm::report_fatal_error(llvm::Twine const&amp;, bool) (/opt/llvm19/bin/clang-19+0x5d537d9)
 #<!-- -->7 0x0000000005d536c6 (/opt/llvm19/bin/clang-19+0x5d536c6)
 #<!-- -->8 0x00000000044ce474 (/opt/llvm19/bin/clang-19+0x44ce474)
 #<!-- -->9 0x0000000006d91d6a llvm::TargetLowering::LowerCallTo(llvm::TargetLowering::CallLoweringInfo&amp;) const (/opt/llvm19/bin/clang-19+0x6d91d6a)
#<!-- -->10 0x0000000006daf6a6 llvm::SelectionDAGBuilder::lowerInvokable(llvm::TargetLowering::CallLoweringInfo&amp;, llvm::BasicBlock const*) (/opt/llvm19/bin/clang-19+0x6daf6a6)
#<!-- -->11 0x0000000006d996ff llvm::SelectionDAGBuilder::LowerCallTo(llvm::CallBase const&amp;, llvm::SDValue, bool, bool, llvm::BasicBlock const*, llvm::TargetLowering::PtrAuthInfo const*) (/opt/llvm19/bin/clang-19+0x6d996ff)
#<!-- -->12 0x0000000006d85950 llvm::SelectionDAGBuilder::visitCall(llvm::CallInst const&amp;) (/opt/llvm19/bin/clang-19+0x6d85950)
#<!-- -->13 0x0000000006d7b106 llvm::SelectionDAGBuilder::visit(llvm::Instruction const&amp;) (/opt/llvm19/bin/clang-19+0x6d7b106)
#<!-- -->14 0x0000000006e16343 llvm::SelectionDAGISel::SelectBasicBlock(llvm::ilist_iterator_w_bits&lt;llvm::ilist_detail::node_options&lt;llvm::Instruction, false, false, void, true, llvm::BasicBlock&gt;, false, true&gt;, llvm::ilist_iterator_w_bits&lt;llvm::ilist_detail::node_options&lt;llvm::Instruction, false, false, void, true, llvm::BasicBlock&gt;, false, true&gt;, bool&amp;) (/opt/llvm19/bin/clang-19+0x6e16343)
#<!-- -->15 0x0000000006e15bdb llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&amp;) (/opt/llvm19/bin/clang-19+0x6e15bdb)
#<!-- -->16 0x0000000006e13de2 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/llvm19/bin/clang-19+0x6e13de2)
#<!-- -->17 0x00000000045a2251 (/opt/llvm19/bin/clang-19+0x45a2251)
#<!-- -->18 0x0000000006e1294e llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&amp;) (/opt/llvm19/bin/clang-19+0x6e1294e)
#<!-- -->19 0x00000000054c97b4 llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) (/opt/llvm19/bin/clang-19+0x54c97b4)
#<!-- -->20 0x00000000058e9ba2 llvm::FPPassManager::runOnFunction(llvm::Function&amp;) (/opt/llvm19/bin/clang-19+0x58e9ba2)
#<!-- -->21 0x00000000058f0a13 llvm::FPPassManager::runOnModule(llvm::Module&amp;) (/opt/llvm19/bin/clang-19+0x58f0a13)
#<!-- -->22 0x00000000058ea896 llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) (/opt/llvm19/bin/clang-19+0x58ea896)
#<!-- -->23 0x00000000064ac252 clang::EmitBackendOutput(clang::DiagnosticsEngine&amp;, clang::HeaderSearchOptions const&amp;, clang::CodeGenOptions const&amp;, clang::TargetOptions const&amp;, clang::LangOptions const&amp;, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr&lt;llvm::vfs::FileSystem&gt;, std::unique_ptr&lt;llvm::raw_pwrite_stream, std::default_delete&lt;llvm::raw_pwrite_stream&gt;&gt;, clang::BackendConsumer*) (/opt/llvm19/bin/clang-19+0x64ac252)
#<!-- -->24 0x00000000064cd0c5 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&amp;) (/opt/llvm19/bin/clang-19+0x64cd0c5)
#<!-- -->25 0x0000000007e368f9 clang::ParseAST(clang::Sema&amp;, bool, bool) (/opt/llvm19/bin/clang-19+0x7e368f9)
#<!-- -->26 0x00000000068e89d6 clang::FrontendAction::Execute() (/opt/llvm19/bin/clang-19+0x68e89d6)
#<!-- -->27 0x0000000006859ba4 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/opt/llvm19/bin/clang-19+0x6859ba4)
#<!-- -->28 0x00000000069b3b7e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/opt/llvm19/bin/clang-19+0x69b3b7e)
#<!-- -->29 0x0000000003db0739 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/opt/llvm19/bin/clang-19+0x3db0739)
#<!-- -->30 0x0000000003dad991 (/opt/llvm19/bin/clang-19+0x3dad991)
#<!-- -->31 0x00000000066a30c9 (/opt/llvm19/bin/clang-19+0x66a30c9)
#<!-- -->32 0x0000000005d4d53c llvm::CrashRecoveryContext::RunSafely(llvm::function_ref&lt;void ()&gt;) (/opt/llvm19/bin/clang-19+0x5d4d53c)
#<!-- -->33 0x00000000066a2b06 clang::driver::CC1Command::Execute(llvm::ArrayRef&lt;std::optional&lt;llvm::StringRef&gt;&gt;, std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt;&gt;*, bool*) const (/opt/llvm19/bin/clang-19+0x66a2b06)
#<!-- -->34 0x0000000006661367 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&amp;, clang::driver::Command const*&amp;, bool) const (/opt/llvm19/bin/clang-19+0x6661367)
#<!-- -->35 0x000000000666180e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;, bool) const (/opt/llvm19/bin/clang-19+0x666180e)
#<!-- -->36 0x000000000667febf clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&amp;, llvm::SmallVectorImpl&lt;std::pair&lt;int, clang::driver::Command const*&gt;&gt;&amp;) (/opt/llvm19/bin/clang-19+0x667febf)
#<!-- -->37 0x0000000003dad06b clang_main(int, char**, llvm::ToolContext const&amp;) (/opt/llvm19/bin/clang-19+0x3dad06b)
#<!-- -->38 0x0000000003dbc0e7 main (/opt/llvm19/bin/clang-19+0x3dbc0e7)
#<!-- -->39 0x00007f8fed239088 __libc_start_call_main (/lib64/libc.so.6+0x2a088)
#<!-- -->40 0x00007f8fed23914b __libc_start_main@<!-- -->GLIBC_2.2.5 (/lib64/libc.so.6+0x2a14b)
#<!-- -->41 0x0000000003dab525 _start (/opt/llvm19/bin/clang-19+0x3dab525)
clang++: error: clang frontend command failed with exit code 70 (use -v to see invocation)
clang version 19.1.0-rc2
Target: armv7-apple-darwin
Thread model: posix
InstalledDir: /opt/llvm19/bin
clang++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++: note: diagnostic msg: /tmp/test-c84746.cpp
clang++: note: diagnostic msg: /tmp/test-c84746.sh
clang++: note: diagnostic msg: 

********************

test-c84746.cpp
test-c84746.sh

[Un1q32]

This doesn't happen anymore on the latest LLVM 20 branch. Hurray!

[Un1q32]

Nevermind its happening again?

[davemgreen]

Is it still an issue in llvm-20? I believe this was fixed on trunk (https://godbolt.org/z/GjsM7c3Ef), in #109943 that sounds like it should have been on the branch.

[Un1q32]

Is it still an issue in llvm-20? I believe this was fixed on trunk (https://godbolt.org/z/GjsM7c3Ef), in #109943 that sounds like it should have been on the branch.

I swear I tested with the RCs and it was fixed, but it's suddenly happening again with my build of 20.1.0 final, I'll do a build of rc1 real quick to check.

[Un1q32]

Oh wait, I found out what's different, -target armv7-apple-ios doesn't crash but manually specifying an iOS version lower then 5 will crash, so -target armv7-apple-ios3 will crash.

[Un1q32]

llvm-project/llvm/lib/Target/ARM/ARMSubtarget.cpp

Line 229 in c72f795

if (isTargetMachO() && isTargetIOS() && getTargetTriple().isOSVersionLT(5, 0))