`--remove-dead-values` pass crashes on any complex enough CIR code

[keryell]

For example with the ClangIR of the day bae7bd9 on https://github.com/llvm/clangir/blob/main/clang/test/CIR/Lowering/ThroughMLIR/scope.cir
This is an old story that CIR is not yet a clean dialect to survive to some usual code analyses and code transformations.

PATH=$LLVM_DIR/build/bin:$PATH $LLVM_DIR/build/bin/cir-opt --remove-dead-values clang/test/CIR/Lowering/ThroughMLIR/scope.cir
cir-opt: /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/../mlir/include/mlir/IR/Operation.h:983: detail::OperandStorage &mlir::Operation::getOperandStorage(): Assertion `hasOperandStorage && "expected operation to have operand storage"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/build/bin/cir-opt --remove-dead-values /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/clang/test/CIR/Lowering/ThroughMLIR/scope.cir
 #0 0x00005f0c58b5708d llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/lib/Support/Unix/Signals.inc:723:11
 #1 0x00005f0c58b5754b PrintStackTraceSignalHandler(void*) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/lib/Support/Unix/Signals.inc:798:1
 #2 0x00005f0c58b556ef llvm::sys::RunSignalHandlers() /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/lib/Support/Signals.cpp:105:5
 #3 0x00005f0c58b57c0e SignalHandler(int) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/lib/Support/Unix/Signals.inc:413:1
 #4 0x0000726998445250 (/lib/x86_64-linux-gnu/libc.so.6+0x45250)
 #5 0x00007269984a3f1c __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #6 0x00007269984a3f1c __pthread_kill_internal ./nptl/pthread_kill.c:78:10
 #7 0x00007269984a3f1c pthread_kill ./nptl/pthread_kill.c:89:10
 #8 0x000072699844519e raise ./signal/../sysdeps/posix/raise.c:27:6
 #9 0x0000726998428902 abort ./stdlib/abort.c:81:7
#10 0x000072699842881e _nl_load_domain ./intl/loadmsgcat.c:1177:9
#11 0x000072699843b7c7 (/lib/x86_64-linux-gnu/libc.so.6+0x3b7c7)
#12 0x00005f0c56d75d5b mlir::Operation::getOperandStorage() /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/../mlir/include/mlir/IR/Operation.h:0:5
#13 0x00005f0c588fa779 mlir::Operation::eraseOperands(llvm::BitVector const&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/include/mlir/IR/Operation.h:362:5
#14 0x00005f0c588f586b (anonymous namespace)::cleanRegionBranchOp(mlir::RegionBranchOpInterface, mlir::dataflow::RunLivenessAnalysis&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Transforms/RemoveDeadValues.cpp:544:25
#15 0x00005f0c588f4d6d (anonymous namespace)::RemoveDeadValues::runOnOperation()::$_1::operator()(mlir::Operation*) const /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Transforms/RemoveDeadValues.cpp:599:5
#16 0x00005f0c588f4cad void llvm::function_ref<void (mlir::Operation*)>::callback_fn<(anonymous namespace)::RemoveDeadValues::runOnOperation()::$_1>(long, mlir::Operation*) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/include/llvm/ADT/STLFunctionalExtras.h:45:5
#17 0x00005f0c5798baa1 llvm::function_ref<void (mlir::Operation*)>::operator()(mlir::Operation*) const /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/include/llvm/ADT/STLFunctionalExtras.h:68:5
#18 0x00005f0c5798ba6d void mlir::detail::walk<mlir::ForwardIterator>(mlir::Operation*, llvm::function_ref<void (mlir::Operation*)>, mlir::WalkOrder) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/include/mlir/IR/Visitors.h:187:1
#19 0x00005f0c5798ba29 void mlir::detail::walk<mlir::ForwardIterator>(mlir::Operation*, llvm::function_ref<void (mlir::Operation*)>, mlir::WalkOrder) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/include/mlir/IR/Visitors.h:179:27
#20 0x00005f0c5798ba29 void mlir::detail::walk<mlir::ForwardIterator>(mlir::Operation*, llvm::function_ref<void (mlir::Operation*)>, mlir::WalkOrder) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/include/mlir/IR/Visitors.h:179:27
#21 0x00005f0c588f4c52 std::enable_if<llvm::is_one_of<mlir::Operation*, mlir::Operation*, mlir::Region*, mlir::Block*>::value, void>::type mlir::detail::walk<(mlir::WalkOrder)1, mlir::ForwardIterator, (anonymous namespace)::RemoveDeadValues::runOnOperation()::$_1, mlir::Operation*, void>(mlir::Operation*, (anonymous namespace)::RemoveDeadValues::runOnOperation()::$_1&&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/include/mlir/IR/Visitors.h:312:3
#22 0x00005f0c588f4a5d std::enable_if<llvm::function_traits<std::decay<(anonymous namespace)::RemoveDeadValues::runOnOperation()::$_1>::type>::num_args == 1, void>::type mlir::Operation::walk<(mlir::WalkOrder)1, mlir::ForwardIterator, (anonymous namespace)::RemoveDeadValues::runOnOperation()::$_1, void>((anonymous namespace)::RemoveDeadValues::runOnOperation()::$_1&&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/include/mlir/IR/Operation.h:794:5
#23 0x00005f0c588f48f9 (anonymous namespace)::RemoveDeadValues::runOnOperation() /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Transforms/RemoveDeadValues.cpp:609:1
#24 0x00005f0c58856994 mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int)::$_1::operator()() const /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Pass/Pass.cpp:0:17
#25 0x00005f0c58856935 void llvm::function_ref<void ()>::callback_fn<mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int)::$_1>(long) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/include/llvm/ADT/STLFunctionalExtras.h:45:5
#26 0x00005f0c585ad539 llvm::function_ref<void ()>::operator()() const /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/include/llvm/ADT/STLFunctionalExtras.h:68:5
#27 0x00005f0c5885957b void mlir::MLIRContext::executeAction<mlir::PassExecutionAction, mlir::Pass&>(llvm::function_ref<void ()>, llvm::ArrayRef<mlir::IRUnit>, mlir::Pass&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/include/mlir/IR/MLIRContext.h:281:3
#28 0x00005f0c58852457 mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Pass/Pass.cpp:532:17
#29 0x00005f0c58852977 mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Pass/Pass.cpp:592:16
#30 0x00005f0c588543b8 mlir::PassManager::runPasses(mlir::Operation*, mlir::AnalysisManager) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Pass/Pass.cpp:905:10
#31 0x00005f0c588542f3 mlir::PassManager::run(mlir::Operation*) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Pass/Pass.cpp:885:60
#32 0x00005f0c587c6abd performActions(llvm::raw_ostream&, std::shared_ptr<llvm::SourceMgr> const&, mlir::MLIRContext*, mlir::MlirOptMainConfig const&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:412:17
#33 0x00005f0c587c6722 processBuffer(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, mlir::MlirOptMainConfig const&, mlir::DialectRegistry&, llvm::ThreadPoolInterface*) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:477:12
#34 0x00005f0c587c651c mlir::MlirOptMain(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, mlir::DialectRegistry&, mlir::MlirOptMainConfig const&)::$_0::operator()(std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&) const /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:560:12
#35 0x00005f0c587c64b6 llvm::LogicalResult llvm::function_ref<llvm::LogicalResult (std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&)>::callback_fn<mlir::MlirOptMain(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, mlir::DialectRegistry&, mlir::MlirOptMainConfig const&)::$_0>(long, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/include/llvm/ADT/STLFunctionalExtras.h:45:12
#36 0x00005f0c59cb3cc2 llvm::function_ref<llvm::LogicalResult (std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&)>::operator()(std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&) const /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/llvm/include/llvm/ADT/STLFunctionalExtras.h:68:12
#37 0x00005f0c59cb32d5 mlir::splitAndProcessBuffer(std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::function_ref<llvm::LogicalResult (std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, llvm::raw_ostream&)>, llvm::raw_ostream&, llvm::StringRef, llvm::StringRef) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Support/ToolUtilities.cpp:27:12
#38 0x00005f0c587c2d43 mlir::MlirOptMain(llvm::raw_ostream&, std::unique_ptr<llvm::MemoryBuffer, std::default_delete<llvm::MemoryBuffer>>, mlir::DialectRegistry&, mlir::MlirOptMainConfig const&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:563:10
#39 0x00005f0c587c30e5 mlir::MlirOptMain(int, char**, llvm::StringRef, llvm::StringRef, mlir::DialectRegistry&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:604:14
#40 0x00005f0c587c32b8 mlir::MlirOptMain(int, char**, llvm::StringRef, mlir::DialectRegistry&) /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/mlir/lib/Tools/mlir-opt/MlirOptMain.cpp:620:10
#41 0x00005f0c56d7363c main /home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/clang/tools/cir-opt/cir-opt.cpp:82:17
#42 0x000072699842a3b8 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#43 0x000072699842a47b call_init ./csu/../csu/libc-start.c:128:20
#44 0x000072699842a47b __libc_start_main ./csu/../csu/libc-start.c:347:5
#45 0x00005f0c56d73355 _start (/home/rkeryell/Xilinx/Projects/LLVM/worktrees/clangir/build/bin/cir-opt+0x1f20355)
[1]    56000 IOT instruction (core dumped)  PATH=$LLVM_DIR/build/bin:$PATH $LLVM_DIR/build/bin/cir-opt  

[bcardosolopes]

Great to see you playing with the MLIR passes and how CIR behave with them. So far we have only tried a few, improvements and enablement of more of these would be great

[orbiri]

I also looked at these things a few months ago, and I believe that CIR will require a non trivial Dialect design work in order to play nicely with the powerful features MLIR has up its sleeve.

I understand that the goal right now is to establish some end-to-end flow, but I also ponder at the complexity each new commit might introduce in such future Dialect designer.

@bcardosolopes - I’d be happy to hear your thoughts :)

[smeenai]

In general it's a known problem that we violate some MLIR invariants until we reach flat CIR, right? Fixing some of those seems difficult until something like https://discourse.llvm.org/t/rfc-region-based-control-flow-with-early-exits-in-mlir/76998 lands. #978 had some good related discussion as well.

We should of course try to make things better here wherever possible, I just wanted to make sure my own understanding was correct.

[keryell]

Handling complicated region semantics changes is difficult but if it can work already for me on code without goto and exception is already enough to start.
This is why I am handling with the low hanging fruits like #1203 or #1164.

[bcardosolopes]

Great news!