wasm-ld crash related to exceptions and LTO

[gl84]

While preparing tests over a custom libpng build I encountered a wasm-ld crash that is triggered through the wasm-ld flags
-mllvm -enable-emscripten-cxx-exceptions -mllvm -enable-emscripten-sjlj:

It seems a recent change creates a crash in wasm-ld (37bf094 works).

@aheejin Do you have an idea?

The stacktrace and invocation is:
wasm-ld: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/include/llvm/IR/Instructions.h:2784: llvm::Value *llvm::PHINode::getIncomingValueForBlock(const llvm::BasicBlock *) const: AssertionIdx >= 0 && "Invalid basic block argument!"' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: /emsdk/upstream/bin/wasm-ld -o catch2_test.wasm test/libcatch2_font_library_main.bc /png/wasm_32/install/lib/libpng.bc -L/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -mllvm -enable-emscripten-cxx-exceptions -mllvm -enable-emscripten-sjlj --import-undefined --export-if-defined=png_destroy_read_struct --export-table -z stack-size=5242880 --initial-memory=16777216 --no-entry --max-memory=16777216 --global-base=1024
1 . Running pass 'Function Pass Manager' on module 'ld-temp.o'.
2 . Running pass 'WebAssembly Instruction Selection' on function '@_ZN5Catch5clara8TextFlowlsERNSt3__213basic_ostreamIcNS2_11char_traitsIcEEEERKNS1_6ColumnE'
#0 0x00007f6d79c931a3 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x19471a3)
#1 0x00007f6d79c90f4e llvm::sys::RunSignalHandlers() (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x1944f4e)
#2 0x00007f6d79c9366f SignalHandler(int) Signals.cpp:0:0
#3 0x00007f6d7c2d53c0 __restore_rt (/usr/lib/x86_64-linux-gnu/libpthread.so.0+0x153c0)
#4 0x00007f6d7803618b raise (/usr/lib/x86_64-linux-gnu/libc.so.6+0x4618b)
#5 0x00007f6d78015859 abort (/usr/lib/x86_64-linux-gnu/libc.so.6+0x25859)
#6 0x00007f6d78015729 (/usr/lib/x86_64-linux-gnu/libc.so.6+0x25729)
#7 0x00007f6d78026f36 (/usr/lib/x86_64-linux-gnu/libc.so.6+0x36f36)
#8 0x00007f6d7a55a788 llvm::SelectionDAGBuilder::HandlePHINodesInSuccessorBlocks(llvm::BasicBlock const*) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x220e788)
#9 0x00007f6d7a559d44 llvm::SelectionDAGBuilder::visit(llvm::Instruction const&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x220dd44)
#10 0x00007f6d7a5f9aa0 llvm::SelectionDAGISel::SelectBasicBlock(llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction, true, false, void>, false, true>, llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction, true, false, void>, false, true>, bool&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x22adaa0)
#11 0x00007f6d7a5f8f1d llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x22acf1d)
#12 0x00007f6d7a5f5751 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x22a9751)
#13 0x00007f6d7a0ce10d llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x1d8210d)
#14 0x00007f6d79e0fcd8 llvm::FPPassManager::runOnFunction(llvm::Function&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x1ac3cd8)
#15 0x00007f6d79e180b1 llvm::FPPassManager::runOnModule(llvm::Module&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x1acc0b1)
#16 0x00007f6d79e107eb llvm::legacy::PassManagerImpl::run(llvm::Module&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x1ac47eb)
#17 0x00007f6d7b4f50a6 codegen(llvm::lto::Config const&, llvm::TargetMachine*, std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_deletellvm::lto::NativeObjectStream > (unsigned int)>, unsigned int, llvm::Module&, llvm::ModuleSummaryIndex const&) LTOBackend.cpp:0:0
#18 0x00007f6d7b4f4562 llvm::lto::backend(llvm::lto::Config const&, std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_deletellvm::lto::NativeObjectStream > (unsigned int)>, unsigned int, llvm::Module&, llvm::ModuleSummaryIndex&) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x31a8562)
#19 0x00007f6d7b4e8546 llvm::lto::LTO::runRegularLTO(std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_deletellvm::lto::NativeObjectStream > (unsigned int)>) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x319c546)
#20 0x00007f6d7b4e7c12 llvm::lto::LTO::run(std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_deletellvm::lto::NativeObjectStream > (unsigned int)>, std::function<std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_deletellvm::lto::NativeObjectStream > (unsigned int)> (unsigned int, llvm::StringRef)>) (/emsdk/upstream/bin/../lib/libLLVM-13git.so+0x319bc12)
#21 0x0000000000765496 lld::wasm::BitcodeCompiler::compile() (/emsdk/upstream/bin/wasm-ld+0x765496)
#22 0x0000000000767189 lld::wasm::SymbolTable::addCombinedLTOObject() (/emsdk/upstream/bin/wasm-ld+0x767189)
#23 0x00000000007508ee lld::wasm::(anonymous namespace)::LinkerDriver::linkerMain(llvm::ArrayRef<char const*>) Driver.cpp:0:0
#24 0x000000000074b4ba lld::wasm::link(llvm::ArrayRef<char const*>, bool, llvm::raw_ostream&, llvm::raw_ostream&) (/emsdk/upstream/bin/wasm-ld+0x74b4ba)
#25 0x00000000003d545e lldMain(int, char const**, llvm::raw_ostream&, llvm::raw_ostream&, bool) lld.cpp:0:0
#26 0x00000000003d4ff3 main (/emsdk/upstream/bin/wasm-ld+0x3d4ff3)
#27 0x00007f6d780170b3 __libc_start_main (/usr/lib/x86_64-linux-gnu/libc.so.6+0x270b3)
#28 0x00000000003d4cda _start (/emsdk/upstream/bin/wasm-ld+0x3d4cda)
Aborted (core dumped)
`

The wasm-ld call that produced the crash
/emsdk/upstream/bin/wasm-ld -o catch2_test.wasm catch2_main.bc /png/wasm_32/install/lib/libpng.bc -L/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -mllvm -enable-emscripten-cxx-exceptions -mllvm -enable-emscripten-sjlj --import-undefined --export-if-defined=png_destroy_read_struct --export-table -z stack-size=5242880 --initial-memory=16777216 --no-entry --max-memory=16777216 --global-base=1024

I'm trying to create a source only repro case.

[gl84]

Additional info: The crash does not occur in release 2.0.26

[aheejin]

Hmm, I don't have a clue looking the stack trace. If you have a repro I'd appreciate that, even if it doesn't crash with the latest release, because it might be a real bug and other changes in 2.0.26 can mask it.

[gl84]

Sure, I'll try to create something reproducible but sadly not before next week. I don't have access to my computer atm.

Are bitcode files ok?

Your help is highly appreciated!

[aheejin]

Yes, anything that I can reproduce the bug with should be fine. Thanks!

[gl84]

With 2.0.29 the wasm-ld crash has vanished.

The first emscripten release that works again has the hash f0ad0cc. It seems your fix for PHI & longjmps fixed my crash.

Many thanks!