[all-commits] [llvm/llvm-project] 87e5d3: [lld][MachO] Handle compact unwind entries with no...

[alx32 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 87e5d3898c2dbc73f9e75aa16be27757e3969f52
      https://github.com/llvm/llvm-project/commit/87e5d3898c2dbc73f9e75aa16be27757e3969f52
  Author: alx32 <103613512+alx32 at users.noreply.github.com>
  Date:   2026-06-09 (Tue, 09 Jun 2026)

  Changed paths:
    M lld/MachO/InputFiles.cpp
    A lld/test/MachO/compact-unwind-local-label.s

  Log Message:
  -----------
  [lld][MachO] Handle compact unwind entries with no matching symbol (#180009)

Context: This change is to support [MachO basic block hot-cold
splitting](https://discourse.llvm.org/t/rfc-support-fsplit-machine-functions-on-macho-arm64/89739)
- though it's presented below outside of this context.

Compact unwind entries can reference function addresses that have no
corresponding symbol in the object's symbol table (e.g. functions with
temporary local labels). Previously, this would trigger an assertion
failure in assert-enabled builds, or silently drop the unwind entry in
release builds, resulting in missing unwind info at runtime.

Fix this by synthesizing a local `Defined` symbol when no symbol exists
at the target address of a compact unwind entry, so that unwind info is
correctly emitted.

[Assisted-by](https://t.ly/Dkjjk): Cursor IDE + claude-opus-4.6-high +
gpt-5.2-xhigh



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