Hello,
So the question is, as the title states… what is the typical good way of debugging errors obtained from analyzing a large IR file?
I’m asking this question because I have finished developing the analysis which converts stack-to-heap, and during my process of testing this on many micro/macro-test applications, I can get it more or less working on small (simple epoll example) to a medium-sized application such as ProFTPD (using wllvm).
However, regarding a larger application such as Apache HTTPD, I get an error like this after analysis completes.
Finished analysis
opt: /home/llvm-project-13/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp:524: unsigned int llvm::ValueEnumerator::getValueID(const llvm::Value*) const: Assertion `I != ValueMap.end() && "Value not in slotcalculator!"' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: /home/llvm-project-13/llvm-build/bin/opt -load /home/build/lib/libstacktoheap.so -load-pass-plugin /home/build/lib/libstacktoheap.so -passes=stacktoheap /home/inputs/httpd.bc -o /home/results/httpd/httpd.bc
#0 0x00005591abaa381f PrintStackTraceSignalHandler(void*) Signals.cpp:0:0
#1 0x00005591abaa0fbe SignalHandler(int) Signals.cpp:0:0
#2 0x00007f3009104730 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12730)
#3 0x00007f3008beb8eb raise /build/glibc-6iIyft/glibc-2.28/signal/../sysdeps/unix/sysv/linux/raise.c:51:1
#4 0x00007f3008bd6535 abort /build/glibc-6iIyft/glibc-2.28/stdlib/abort.c:81:7
#5 0x00007f3008bd640f _nl_load_domain /build/glibc-6iIyft/glibc-2.28/intl/loadmsgcat.c:1177:9
#6 0x00007f3008be41a2 (/lib/x86_64-linux-gnu/libc.so.6+0x301a2)
#7 0x00005591aab9e131 llvm::ValueEnumerator::getValueID(llvm::Value const*) const (/home/llvm-project-13/llvm-build/bin/opt+0x121f131)
#8 0x00005591aab87038 (anonymous namespace)::ModuleBitcodeWriter::writeInstruction(llvm::Instruction const&, unsigned int, llvm::SmallVectorImpl<unsigned int>&) BitcodeWriter.cpp:0:0
#9 0x00005591aab93819 (anonymous namespace)::ModuleBitcodeWriter::write() BitcodeWriter.cpp:0:0
#10 0x00005591aab959fa llvm::BitcodeWriter::writeModule(llvm::Module const&, bool, llvm::ModuleSummaryIndex const*, bool, std::array<unsigned int, 5ul>*) (/home/llvm-project-13/llvm-build/bin/opt+0x12169fa)
#11 0x00005591aab95bbd llvm::WriteBitcodeToFile(llvm::Module const&, llvm::raw_ostream&, bool, llvm::ModuleSummaryIndex const*, bool, std::array<unsigned int, 5ul>*) (/home/llvm-project-13/llvm-build/bin/opt+0x1216bbd)
#12 0x00005591aab799f8 llvm::BitcodeWriterPass::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/llvm-project-13/llvm-build/bin/opt+0x11fa9f8)
#13 0x00005591aa00d0ed llvm::detail::PassModel<llvm::Module, llvm::BitcodeWriterPass, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::Module> >::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/llvm-project-13/llvm-build/bin/opt+0x68e0ed)
#14 0x00005591ab21c947 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module> >::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/llvm-project-13/llvm-build/bin/opt+0x189d947)
#15 0x00005591aa0176cc llvm::runPassPipeline(llvm::StringRef, llvm::Module&, llvm::TargetMachine*, llvm::TargetLibraryInfoImpl*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::StringRef, llvm::ArrayRef<llvm::StringRef>, llvm::opt_tool::OutputKind, llvm::opt_tool::VerifierKind, bool, bool, bool, bool, bool) (/home/llvm-project-13/llvm-build/bin/opt+0x6986cc)
#16 0x00005591a9f9cc1f main (/home/llvm-project-13/llvm-build/bin/opt+0x61dc1f)
#17 0x00007f3008bd809b __libc_start_main /build/glibc-6iIyft/glibc-2.28/csu/../csu/libc-start.c:342:3
#18 0x00005591aa00b0fa _start (/home/llvm-project-13/llvm-build/bin/opt+0x68c0fa)
tag.sh: line 28: 51567 Aborted $LLVM_DIR/bin/opt -load $LIB_DIR/libstacktoheap.so -load-pass-plugin $LIB_DIR/libstacktoheap.so -passes=stacktoheap $INPUT_FILE_LOC -o $RESULTS_FILE_LOC
clang-13: error: no such file or directory: '/home/results/httpd/httpd.bc'
clang-13: error: no input files
clang-13: error: no such file or directory: '/home/results/httpd/httpd.bc'
/home/llvm-project-13/llvm-build/bin/llvm-dis: error: No such file or directory
For what it is worth, I feel this might have something to do with me trying to rewrite a bitcode using an input of a single file (I don’t think this is related to wllvm at all, but just that I’m trying to perform rewriting analysis on a bitcode file with everything combined which can/could break dependencies that were linked during wllvm process).
There are a few hints here and there in this error log, such as this error is happening near ModuleBitcodeWriter::writeInstruction, which means the analysis is completed in terms of instrumenting instructions and whatnot but cannot generate the new IR.
My last thought is that I am certain that although the analysis successfully completes, it must have done something wrong during inserting/removing instructions. Still, because this error log is happening after the analysis, I’m a bit lost on how to start debugging through this.
I would appreciate any tips on how to get started on deep-dive debugging of LLVM analysis for the cases like this.