[llvm] [VPlan] Build initial VPlan 0 using HCFGBuilder for inner loops. (NFC) (PR #124432)

[Mikael Holmén via llvm-commits]

mikaelholmen wrote:

> I'm getting an assertion failure after this commit when using llvm on Linux and Windows. I can create a reproducer if that's useful.
> 
> ```
> Assertion failed: i < getNumSuccessors() && "Successor # out of range for Branch!", file /workspace/srcdir/llvm-project/llvm/include/llvm/IR/Instructions.h, line 3117
> 
> [5772] signal 22: SIGABRT
> in expression starting at none:0
> crt_sig_handler at D:/a/llvm_julia_tester/llvm_julia_tester/julia/src\signals-win.c:104
> raise at C:\Windows\System32\msvcrt.dll (unknown line)
> abort at C:\Windows\System32\msvcrt.dll (unknown line)
> assert at C:\Windows\System32\msvcrt.dll (unknown line)
> _ZN12_GLOBAL__N_115PlainCFGBuilder13buildPlainCFGERN4llvm8DenseMapIPNS1_11VPBlockBaseEPNS1_10BasicBlockENS1_12DenseMapInfoIS4_vEENS1_6detail12DenseMapPairIS4_S6_EEEE at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZN4llvm16VPlanHCFGBuilder13buildPlainCFGEv at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZN4llvm16VPlanHCFGBuilder20buildHierarchicalCFGEv at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZN4llvm24LoopVectorizationPlanner24buildVPlansWithVPRecipesENS_12ElementCountES1_ at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZN4llvm24LoopVectorizationPlanner4planENS_12ElementCountEj at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZNK4llvm8LoopBaseINS_10BasicBlockENS_4LoopEE14getLoopLatchesERNS_15SmallVectorImplIPS1_EE at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZN4llvm28getOptionalBoolLoopAttributeEPKNS_4LoopENS_9StringRefE at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZN4llvm17LoopVectorizePass7runImplERNS_8FunctionE at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> _ZN4llvm17LoopVectorizePass3runERNS_8FunctionERNS_15AnalysisManagerIS1_JEEE at D:\a\llvm_julia_tester\llvm_julia_tester\julia\usr\bin\libLLVM-21jl.dll (unknown line)
> ```

Hi @fhahn 
We see that crash as well.
Reproduce with
```opt -passes=loop-vectorize bbi-104312.ll -o /dev/null```
[bbi-104312.ll.gz](https://github.com/user-attachments/files/18865403/bbi-104312.ll.gz)


https://github.com/llvm/llvm-project/pull/124432