[llvm] [BranchFolding] Merge debug locs on common hoisted code (PR #140063)

[Mikael Holmén via llvm-commits]

mikaelholmen wrote:

Hi @OCHyams 

I started seeing crashes with this patch for my downstream target. I managed to reduce and then reproduce it for ARM with
```llc -mtriple=armv7-apple-ios bbi-107255_arm.mir -o - -run-pass=branch-folder```

It crashes with
```
llc: ../lib/CodeGen/BranchFolding.cpp:2097: bool llvm::BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *): Assertion `TI->isIdenticalTo(*FI, MachineInstr::CheckDefs) && "Expected non-debug lockstep"' 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/llc -mtriple=armv7-apple-ios bbi-107255_arm.mir -o - -run-pass=branch-folder
1.	Running pass 'Function Pass Manager' on module 'bbi-107255_arm.mir'.
2.	Running pass 'Control Flow Optimizer' on function '@f_1418_2054'
 #0 0x00005629c40322a6 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (build-all/bin/llc+0x76d22a6)
 #1 0x00005629c402fd8e llvm::sys::RunSignalHandlers() (build-all/bin/llc+0x76cfd8e)
 #2 0x00005629c40329d9 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #3 0x00007fa8fc4c7d10 __restore_rt (/lib64/libpthread.so.0+0x12d10)
 #4 0x00007fa8f9e6752f raise (/lib64/libc.so.6+0x4e52f)
 #5 0x00007fa8f9e3ae65 abort (/lib64/libc.so.6+0x21e65)
 #6 0x00007fa8f9e3ad39 _nl_load_domain.cold.0 (/lib64/libc.so.6+0x21d39)
 #7 0x00007fa8f9e5fe86 (/lib64/libc.so.6+0x46e86)
 #8 0x00005629c2e5c974 llvm::BranchFolder::HoistCommonCodeInSuccs(llvm::MachineBasicBlock*) BranchFolding.cpp:0:0
 #9 0x00005629c2e53c25 llvm::BranchFolder::OptimizeFunction(llvm::MachineFunction&, llvm::TargetInstrInfo const*, llvm::TargetRegisterInfo const*, llvm::MachineLoopInfo*, bool) BranchFolding.cpp:0:0
#10 0x00005629c2e5d10b (anonymous namespace)::BranchFolderLegacy::runOnMachineFunction(llvm::MachineFunction&) BranchFolding.cpp:0:0
#11 0x00005629c3062c67 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (build-all/bin/llc+0x6702c67)
#12 0x00005629c35bb3d9 llvm::FPPassManager::runOnFunction(llvm::Function&) (build-all/bin/llc+0x6c5b3d9)
#13 0x00005629c35c39d2 llvm::FPPassManager::runOnModule(llvm::Module&) (build-all/bin/llc+0x6c639d2)
#14 0x00005629c35bbeb8 llvm::legacy::PassManagerImpl::run(llvm::Module&) (build-all/bin/llc+0x6c5beb8)
#15 0x00005629c0fcf6dd compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#16 0x00005629c0fccdc0 main (build-all/bin/llc+0x466cdc0)
#17 0x00007fa8f9e537e5 __libc_start_main (/lib64/libc.so.6+0x3a7e5)
#18 0x00005629c0fcc22e _start (build-all/bin/llc+0x466c22e)
Abort (core dumped)
```
[bbi-107255_arm.mir.gz](https://github.com/user-attachments/files/20382281/bbi-107255_arm.mir.gz)


https://github.com/llvm/llvm-project/pull/140063