[PATCH] D104827: [DebugInfo] Enforce implicit constraints on `distinct` MDNodes

[Scott Linder via Phabricator via llvm-commits]

scott.linder added a comment.

In D104827#3119839 <https://reviews.llvm.org/D104827#3119839>, @aeubanks wrote:

> hi, this is causing crashes
>
>   $ build/rel/bin/opt -passes='thinlto-pre-link<O2>' /tmp/a.ll -o /dev/null
>   opt: ../../llvm/include/llvm/IR/Metadata.def:180: void (anonymous namespace)::ModuleBitcodeWriter::writeMetadataRecords(ArrayRef<const llvm::Metadata *>, SmallVectorImpl<uint64_t> &, std::vector<
>   unsigned int> *, std::vector<uint64_t> *): Assertion `!N->isDistinct() && "Expected non-distinct " "DIArgList"' failed.                                                                            
>   PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.                                                                                                              
>   Stack dump:                                                                                                                                                                                        
>   0.      Program arguments: build/rel/bin/opt -passes=thinlto-pre-link<O2> /tmp/a.ll -o /dev/null                                                                                                   
>    #0 0x0000000001f37a13 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Support/Unix/Signals.inc:565:13             
>    #1 0x0000000001f3588e llvm::sys::RunSignalHandlers() /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Support/Signals.cpp:98:18                                        
>    #2 0x0000000001f37d7f SignalHandler(int) /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Support/Unix/Signals.inc:407:1                                               
>    #3 0x00007f2003b8e8e0 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x138e0)                                                                                                                
>    #4 0x00007f2003668e71 raise ./signal/../sysdeps/unix/sysv/linux/raise.c:50:1                                                                                                                      
>    #5 0x00007f2003652536 abort ./stdlib/abort.c:81:7                                                                                                                                                 
>    #6 0x00007f200365241f get_sysdep_segment_value ./intl/loadmsgcat.c:509:8                                                                                                                          
>    #7 0x00007f200365241f _nl_load_domain ./intl/loadmsgcat.c:970:34                                                                                                                                  
>    #8 0x00007f20036617f2 (/lib/x86_64-linux-gnu/libc.so.6+0x357f2)                                                                                                                                   
>    #9 0x000000000168e506 (anonymous namespace)::ModuleBitcodeWriter::writeMetadataRecords(llvm::ArrayRef<llvm::Metadata const*>, llvm::SmallVectorImpl<unsigned long>&, std::vector<unsigned int, std::allocator<unsigned int> >*, std::vector<unsigned long, std::allocator<unsigned long> >*) /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/include/llvm/IR/Metadata.def:0:0
>   #10 0x000000000167df15 writeFunctionMetadata /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Bitcode/Writer/BitcodeWriter.cpp:2303:3
>   #11 0x000000000167df15 writeFunction /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Bitcode/Writer/BitcodeWriter.cpp:3351:3
>   #12 0x000000000167df15 (anonymous namespace)::ModuleBitcodeWriter::write() /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Bitcode/Writer/BitcodeWriter.cpp:4448:7
>   #13 0x0000000001677d32 ~ModuleBitcodeWriterBase /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Bitcode/Writer/BitcodeWriter.cpp:155:7
>   #14 0x0000000001677d32 llvm::BitcodeWriter::writeModule(llvm::Module const&, bool, llvm::ModuleSummaryIndex const*, bool, std::array<unsigned int, 5ul>*) /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Bitcode/Writer/BitcodeWriter.cpp:4626:1
>   #15 0x00000000016813cb llvm::WriteBitcodeToFile(llvm::Module const&, llvm::raw_ostream&, bool, llvm::ModuleSummaryIndex const*, bool, std::array<unsigned int, 5ul>*) /usr/local/google/home/aeubanks/repos/llvm-project/build/rel/../../llvm/lib/Bitcode/Writer/BitcodeWriter.cpp:4653:10
>
> F20190023: a.ll <https://reviews.llvm.org/F20190023>
>
> (I tried reducing as much as possible but there's still a lot of debug info)

Thank you for the reproducer! It seems like one of my fundamental assumptions about how LLVM handles metadata was faulty.

I assumed that uniqued nodes couldn't "become distinct", but they evidently can due to things like RAUW. I'll try to get a better grasp on what the rules actually are and then update the review.


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