[llvm-branch-commits] [lldb] Handle backwards branches in UnwindAssemblyInstEmulation (PR #169633)

[Felipe de Azevedo Piovezan via llvm-branch-commits]

https://github.com/felipepiovezan created https://github.com/llvm/llvm-project/pull/169633

This allows the unwinder to handle code with mid-function epilogues
where the subsequent code is reachable through a backwards branch.

Two changes are required to accomplish this:

1. Do not enqueue the subsequent instruction if the current instruction
   is a barrier(*).
2. When processing an instruction, stop ignoring branches with negative
   offsets.

(*) As per the definition in LLVM's MC layer, a barrier is any
instruction that "stops control flow from executing the instruction
immediately following it". See `MCInstrDesc::isBarrier` in MCInstrDesc.h

commit-id:fd266c13