[llvm] [SLP]Make PHICompare comparator follow weak strict ordering requirement (PR #110529)

[Mikael Holmén via llvm-commits]

mikaelholmen wrote:

Hi,

I bisected a crash back to this commit.
Reproduce with:
```opt -passes="slp-vectorizer" -mtriple=aarch64 bbi-104215.ll -o /dev/null```
Result:
```
opt: ../lib/Transforms/Vectorize/SLPVectorizer.cpp:5730: auto llvm::slpvectorizer::BoUpSLP::getReorderingData(const TreeEntry &, bool)::(anonymous class)::operator()(BasicBlock *, BasicBlock *) const: Assertion `NodeB && "Should only process reachable instructions"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: build-all/bin/opt -passes=slp-vectorizer -mtriple=aarch64 bbi-104215.ll -o /dev/null
1.	Running pass "function(slp-vectorizer)" on module "bbi-104215.ll"
2.	Running pass "slp-vectorizer" on function "f_180_2259"
 #0 0x00005602853a5026 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (build-all/bin/opt+0x4646026)
 #1 0x00005602853a2a6e llvm::sys::RunSignalHandlers() (build-all/bin/opt+0x4643a6e)
 #2 0x00005602853a58a9 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #3 0x00007f5db37acd10 __restore_rt (/lib64/libpthread.so.0+0x12d10)
 #4 0x00007f5db114c52f raise (/lib64/libc.so.6+0x4e52f)
 #5 0x00007f5db111fe65 abort (/lib64/libc.so.6+0x21e65)
 #6 0x00007f5db111fd39 _nl_load_domain.cold.0 (/lib64/libc.so.6+0x21d39)
 #7 0x00007f5db1144e86 (/lib64/libc.so.6+0x46e86)
 #8 0x0000560286e891cd llvm::slpvectorizer::BoUpSLP::getReorderingData(llvm::slpvectorizer::BoUpSLP::TreeEntry const&, bool)::$_6::operator()(llvm::BasicBlock*, llvm::BasicBlock*) const SLPVectorizer.cpp:0:0
 #9 0x0000560286e8887d void std::__merge_adaptive<unsigned int*, long, unsigned int*, __gnu_cxx::__ops::_Iter_comp_iter<llvm::slpvectorizer::BoUpSLP::getReorderingData(llvm::slpvectorizer::BoUpSLP::TreeEntry const&, bool)::$_7>>(unsigned int*, unsigned int*, unsigned int*, long, long, unsigned int*, __gnu_cxx::__ops::_Iter_comp_iter<llvm::slpvectorizer::BoUpSLP::getReorderingData(llvm::slpvectorizer::BoUpSLP::TreeEntry const&, bool)::$_7>) SLPVectorizer.cpp:0:0
#10 0x0000560286dd42b3 llvm::slpvectorizer::BoUpSLP::getReorderingData(llvm::slpvectorizer::BoUpSLP::TreeEntry const&, bool) (build-all/bin/opt+0x60752b3)
#11 0x0000560286dd8354 llvm::slpvectorizer::BoUpSLP::reorderTopToBottom() (build-all/bin/opt+0x6079354)
#12 0x0000560286e3ff0c llvm::SLPVectorizerPass::tryToVectorizeList(llvm::ArrayRef<llvm::Value*>, llvm::slpvectorizer::BoUpSLP&, bool) (build-all/bin/opt+0x60e0f0c)
#13 0x0000560286e45a04 bool tryToVectorizeSequence<llvm::Value>(llvm::SmallVectorImpl<llvm::Value*>&, llvm::function_ref<bool (llvm::Value*, llvm::Value*)>, llvm::function_ref<bool (llvm::Value*, llvm::Value*)>, llvm::function_ref<bool (llvm::ArrayRef<llvm::Value*>, bool)>, bool, llvm::slpvectorizer::BoUpSLP&) SLPVectorizer.cpp:0:0
#14 0x0000560286e3819e llvm::SLPVectorizerPass::vectorizeChainsInBlock(llvm::BasicBlock*, llvm::slpvectorizer::BoUpSLP&) (build-all/bin/opt+0x60d919e)
#15 0x0000560286e35c64 llvm::SLPVectorizerPass::runImpl(llvm::Function&, llvm::ScalarEvolution*, llvm::TargetTransformInfo*, llvm::TargetLibraryInfo*, llvm::AAResults*, llvm::LoopInfo*, llvm::DominatorTree*, llvm::AssumptionCache*, llvm::DemandedBits*, llvm::OptimizationRemarkEmitter*) (build-all/bin/opt+0x60d6c64)
#16 0x0000560286e351e7 llvm::SLPVectorizerPass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (build-all/bin/opt+0x60d61e7)
#17 0x000056028682b6cd llvm::detail::PassModel<llvm::Function, llvm::SLPVectorizerPass, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) PassBuilderPipelines.cpp:0:0
#18 0x00005602855c75c7 llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (build-all/bin/opt+0x48685c7)
#19 0x00005602868220fd llvm::detail::PassModel<llvm::Function, llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) PassBuilderPipelines.cpp:0:0
#20 0x00005602855cc19e llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (build-all/bin/opt+0x486d19e)
#21 0x00005602868187ed llvm::detail::PassModel<llvm::Module, llvm::ModuleToFunctionPassAdaptor, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) PassBuilderPipelines.cpp:0:0
#22 0x00005602855c62b7 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (build-all/bin/opt+0x48672b7)
#23 0x00005602867a3b5c llvm::runPassPipeline(llvm::StringRef, llvm::Module&, llvm::TargetMachine*, llvm::TargetLibraryInfoImpl*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::StringRef, llvm::ArrayRef<llvm::PassPlugin>, llvm::ArrayRef<std::function<void (llvm::PassBuilder&)>>, llvm::opt_tool::OutputKind, llvm::opt_tool::VerifierKind, bool, bool, bool, bool, bool, bool, bool) (build-all/bin/opt+0x5a44b5c)
#24 0x0000560285367c12 optMain (build-all/bin/opt+0x4608c12)
#25 0x00007f5db11387e5 __libc_start_main (/lib64/libc.so.6+0x3a7e5)
#26 0x000056028536582e _start (build-all/bin/opt+0x460682e)
Abort (core dumped)
```
[bbi-104215.ll.gz](https://github.com/user-attachments/files/18839931/bbi-104215.ll.gz)


https://github.com/llvm/llvm-project/pull/110529