Dedup iterator invalidation bug

Nobody has claimed this yet.

## Summary

Dedup pass appears to still have a safety issue re:early-inc/post-order iterators over a mutated instance graph.

Ran into this using a recent (post-1.4.0) firtool, reported by ASAN.

## Details

ASAN report

```
=================================================================
==830554==ERROR: AddressSanitizer: heap-use-after-free on address 0x61600014c2a0 at pc 0x000001255169 bp 0x7ffd1e196e90 sp 0x7ffd1e196e88
READ of size 8 at 0x61600014c2a0 thread T0
#0 0x1255168 in (anonymous namespace)::DedupPass::runOnOperation() /home/will/src/sifive/circt/lib/Dialect/FIRRTL/Transforms/Dedup.cpp:1190:21
#1 0x228db02 in mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:470:11
#2 0x228f2b3 in mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:534:16
#3 0x22a22af in mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool)::$_12::operator()(mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool)::OpPMInfo&) const /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:754:36
#4 0x22924e2 in failableParallelForEach<__gnu_cxx::__normal_iterator > >, (lambda at /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:744:20) &> /home/will/src/sifive/circt/llvm/mlir/include/mlir/IR/Threading.h:46:18
#5 0x22924e2 in failableParallelForEach > &, (lambda at /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:744:20) &> /home/will/src/sifive/circt/llvm/mlir/include/mlir/IR/Threading.h:92:10
#6 0x22924e2 in mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:764:14
#7 0x228de03 in runOnOperation /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:655:5
#8 0x228de03 in mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:468:14
#9 0x228f2b3 in mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:534:16
#10 0x2295522 in runPasses /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:837:10
#11 0x2295522 in mlir::PassManager::run(mlir::Operation*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:817:60
#12 0xdb6bf6 in processBuffer(mlir::MLIRContext&, mlir::TimingScope&, llvm::SourceMgr&, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:624:17
#13 0xdb3cba in processInputSplit(mlir::MLIRContext&, mlir::TimingScope&, std::unique_ptr >, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:714:12
#14 0xdb388e in processInput(mlir::MLIRContext&, mlir::TimingScope&, std::unique_ptr >, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:730:12
#15 0xdb34f4 in executeFirtool(mlir::MLIRContext&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:811:14
#16 0xdb2bed in main /home/will/src/sifive/circt/tools/firtool/firtool.cpp:846:17
#17 0x7f0a01f6b236 in __libc_start_call_main (/nix/store/lyl6nysc3i3aqhj6shizjgj0ibnf1pvg-glibc-2.34-210/lib/libc.so.6+0x29236) (BuildId: c512f38583c48b03cc0011d4583d15cea2e94d03)
#18 0x7f0a01f6b2f4 in __libc_start_main@GLIBC_2.2.5 (/nix/store/lyl6nysc3i3aqhj6shizjgj0ibnf1pvg-glibc-2.34-210/lib/libc.so.6+0x292f4) (BuildId: c512f38583c48b03cc0011d4583d15cea2e94d03)
#19 0xcbbf70 in _start /build/glibc-2.34/csu/../sysdeps/x86_64/start.S:116

0x61600014c2a0 is located 288 bytes inside of 544-byte region [0x61600014c180,0x61600014c3a0)
freed by thread T0 here:
LLVMSymbolizer: error reading file: No such file or directory
#0 0xd6b597 in __interceptor_free.part.0 static-reloc.c
#1 0x125ac5a in llvm::po_iterator, false, llvm::GraphTraits >::~po_iterator() /home/will/src/sifive/circt/llvm/llvm/include/llvm/ADT/PostOrderIterator.h:96:7
#2 0x125ac5a in llvm::early_inc_iterator_impl, false, llvm::GraphTraits > >::operator*() /home/will/src/sifive/circt/llvm/llvm/include/llvm/ADT/STLExtras.h:573:5
#3 0x125490e in (anonymous namespace)::DedupPass::runOnOperation() /home/will/src/sifive/circt/lib/Dialect/FIRRTL/Transforms/Dedup.cpp:1190:21
#4 0x228db02 in mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:470:11
#5 0x228f2b3 in mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:534:16
#6 0x22a22af in mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool)::$_12::operator()(mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool)::OpPMInfo&) const /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:754:36
#7 0x22924e2 in failableParallelForEach<__gnu_cxx::__normal_iterator > >, (lambda at /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:744:20) &> /home/will/src/sifive/circt/llvm/mlir/include/mlir/IR/Threading.h:46:18
#8 0x22924e2 in failableParallelForEach > &, (lambda at /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:744:20) &> /home/will/src/sifive/circt/llvm/mlir/include/mlir/IR/Threading.h:92:10
#9 0x22924e2 in mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:764:14
#10 0x228de03 in runOnOperation /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:655:5
#11 0x228de03 in mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:468:14
#12 0x228f2b3 in mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:534:16
#13 0x2295522 in runPasses /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:837:10
#14 0x2295522 in mlir::PassManager::run(mlir::Operation*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:817:60
#15 0xdb6bf6 in processBuffer(mlir::MLIRContext&, mlir::TimingScope&, llvm::SourceMgr&, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:624:17
#16 0xdb3cba in processInputSplit(mlir::MLIRContext&, mlir::TimingScope&, std::unique_ptr >, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:714:12
#17 0xdb388e in processInput(mlir::MLIRContext&, mlir::TimingScope&, std::unique_ptr >, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:730:12
#18 0xdb34f4 in executeFirtool(mlir::MLIRContext&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:811:14
#19 0xdb2bed in main /home/will/src/sifive/circt/tools/firtool/firtool.cpp:846:17
#20 0x7f0a01f6b236 in __libc_start_call_main (/nix/store/lyl6nysc3i3aqhj6shizjgj0ibnf1pvg-glibc-2.34-210/lib/libc.so.6+0x29236) (BuildId: c512f38583c48b03cc0011d4583d15cea2e94d03)
#21 0x7ffd1e19b8e5 ([stack]+0x428e5)

previously allocated by thread T0 here:
#0 0xd6c49f in malloc (/home/will/src/sifive/circt/build-asan/bin/firtool+0xd6c49f)
#1 0xe3a545 in safe_malloc /home/will/src/sifive/circt/llvm/llvm/include/llvm/Support/MemAlloc.h:26:18
#2 0xe3a545 in llvm::SmallVectorBase::grow_pod(void*, unsigned long, unsigned long) /home/will/src/sifive/circt/llvm/llvm/lib/Support/SmallVector.cpp:126:15
#3 0x1209a03 in llvm::SmallVectorTemplateCommon, false, false> >, circt::hw::InstanceGraphNode* (*)(circt::hw::InstanceRecord const*), circt::hw::InstanceGraphNode*> >, void>::grow_pod(unsigned long, unsigned long) /home/will/src/sifive/circt/llvm/llvm/include/llvm/ADT/SmallVector.h:120:11
#4 0x1209a03 in llvm::SmallVectorTemplateBase, false, false> >, circt::hw::InstanceGraphNode* (*)(circt::hw::InstanceRecord const*), circt::hw::InstanceGraphNode*> >, true>::grow(unsigned long) /home/will/src/sifive/circt/llvm/llvm/include/llvm/ADT/SmallVector.h:506:41
#5 0x1209a03 in llvm::SmallVectorImpl, false, false> >, circt::hw::InstanceGraphNode* (*)(circt::hw::InstanceRecord const*), circt::hw::InstanceGraphNode*> > >::operator=(llvm::SmallVectorImpl, false, false> >, circt::hw::InstanceGraphNode* (*)(circt::hw::InstanceRecord const*), circt::hw::InstanceGraphNode*> > > const&) /home/will/src/sifive/circt/llvm/llvm/include/llvm/ADT/SmallVector.h:1026:11
#6 0x125ac3e in llvm::po_iterator, false, llvm::GraphTraits >::operator++(int) /home/will/src/sifive/circt/llvm/llvm/include/llvm/ADT/PostOrderIterator.h:176:23
#7 0x125ac3e in llvm::early_inc_iterator_impl, false, llvm::GraphTraits > >::operator*() /home/will/src/sifive/circt/llvm/llvm/include/llvm/ADT/STLExtras.h:573:13
#8 0x125490e in (anonymous namespace)::DedupPass::runOnOperation() /home/will/src/sifive/circt/lib/Dialect/FIRRTL/Transforms/Dedup.cpp:1190:21
#9 0x228db02 in mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:470:11
#10 0x228f2b3 in mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:534:16
#11 0x22a22af in mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool)::$_12::operator()(mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool)::OpPMInfo&) const /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:754:36
#12 0x22924e2 in failableParallelForEach<__gnu_cxx::__normal_iterator > >, (lambda at /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:744:20) &> /home/will/src/sifive/circt/llvm/mlir/include/mlir/IR/Threading.h:46:18
#13 0x22924e2 in failableParallelForEach > &, (lambda at /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:744:20) &> /home/will/src/sifive/circt/llvm/mlir/include/mlir/IR/Threading.h:92:10
#14 0x22924e2 in mlir::detail::OpToOpPassAdaptor::runOnOperationAsyncImpl(bool) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:764:14
#15 0x228de03 in runOnOperation /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:655:5
#16 0x228de03 in mlir::detail::OpToOpPassAdaptor::run(mlir::Pass*, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:468:14
#17 0x228f2b3 in mlir::detail::OpToOpPassAdaptor::runPipeline(mlir::OpPassManager&, mlir::Operation*, mlir::AnalysisManager, bool, unsigned int, mlir::PassInstrumentor*, mlir::PassInstrumentation::PipelineParentInfo const*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:534:16
#18 0x2295522 in runPasses /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:837:10
#19 0x2295522 in mlir::PassManager::run(mlir::Operation*) /home/will/src/sifive/circt/llvm/mlir/lib/Pass/Pass.cpp:817:60
#20 0xdb6bf6 in processBuffer(mlir::MLIRContext&, mlir::TimingScope&, llvm::SourceMgr&, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:624:17
#21 0xdb3cba in processInputSplit(mlir::MLIRContext&, mlir::TimingScope&, std::unique_ptr >, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:714:12
#22 0xdb388e in processInput(mlir::MLIRContext&, mlir::TimingScope&, std::unique_ptr >, llvm::Optional > >&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:730:12
#23 0xdb34f4 in executeFirtool(mlir::MLIRContext&) /home/will/src/sifive/circt/tools/firtool/firtool.cpp:811:14
#24 0xdb2bed in main /home/will/src/sifive/circt/tools/firtool/firtool.cpp:846:17
#25 0x7f0a01f6b236 in __libc_start_call_main (/nix/store/lyl6nysc3i3aqhj6shizjgj0ibnf1pvg-glibc-2.34-210/lib/libc.so.6+0x29236) (BuildId: c512f38583c48b03cc0011d4583d15cea2e94d03)
#26 0x7ffd1e19b8e5 ([stack]+0x428e5)
```

The `SmallVector` of `pair`s looks to be the visit stack stored in post-order iterators.

So it looks like the post-order iterator's state -- despite (because of?) `make_early_inc_range` wrapping it-- does not work well when mutating the underlying graph. (Would external storage would help?)

Start in lib/Dialect/FIRRTL/Transforms/Dedup.cpp at line 1190, using the supplied ASAN trace to inspect the DedupPass traversal and its early-increment/post-order iterator behavior. Reproduce the report with firtool and confirm the dedup pass no longer produces the reported heap-use-after-free under ASAN.

Written by the indexing model from the issue text.