[all-commits] [llvm/llvm-project] 4e4763: [lldb] Handle backwards branches in UnwindAssembly...

[Felipe de Azevedo Piovezan via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4e4763a8a4659dc252429a003c613f762d5a1083
      https://github.com/llvm/llvm-project/commit/4e4763a8a4659dc252429a003c613f762d5a1083
  Author: Felipe de Azevedo Piovezan <fpiovezan at apple.com>
  Date:   2025-12-03 (Wed, 03 Dec 2025)

  Changed paths:
    M lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
    M lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.h
    M lldb/unittests/UnwindAssembly/ARM64/TestArm64InstEmulation.cpp

  Log Message:
  -----------
  [lldb] Handle backwards branches in UnwindAssemblyInstEmulation (#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

Part of a sequence of PRs:
[lldb][NFCI] Rewrite UnwindAssemblyInstEmulation in terms of a CFG visit
#169630
[lldb][NFC] Rename forward_branch_offset to branch_offset in
UnwindAssemblyInstEmulation #169631
[lldb] Add DisassemblerLLVMC::IsBarrier API #169632
[lldb] Handle backwards branches in UnwindAssemblyInstEmulation #169633

commit-id:fd266c13



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