[lld] [LLD, MachO] Add `getUnwindInfoEncodingHash` to `BPSectionOrderer.cpp`. (PR #105587)

[Ellis Hoag via llvm-commits]

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@@ -34,6 +34,17 @@ class UnwindInfoSection : public SyntheticSection {
 
 UnwindInfoSection *makeUnwindInfoSection();
 
+// LLD's internal representation of a compact unwind entry.
+struct CompactUnwindEntry {
+  uint64_t functionAddress;
+  uint32_t functionLength;
+  compact_unwind_encoding_t encoding;
+  Symbol *personality;
+  InputSection *lsda;
+
+  void relocateOneCompactUnwindEntry(const Defined *d);
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ellishg wrote:

I wish this function could return `std::optional<CompactUnwindEntry>`, but it looks like we need to set `functionAddress` even if there is no unwind entry (I wonder if this really is required). 

At the very least, can you add a comment explaining what this function does?

https://github.com/llvm/llvm-project/pull/105587