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

[Peter Rong via llvm-commits]

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@@ -60,6 +61,33 @@ getRelocHash(const Reloc &reloc,
   return getRelocHash(kind, sectionIdx.value_or(0), 0, reloc.addend);
 }
 
+// Get a hash of the unwind info (after relocation).
+// This hash is not 100% accurate, but it's good enough for compression.
+//
+// Unwind info will be eliminated if it is the same with its neighboors.
+// We want to order functions such that the ones with similar unwind info
+// can stay together.
+// See more here:
+// https://faultlore.com/blah/compact-unwinding/#page-tables
+static uint64_t getUnwindInfoEncodingHash(const InputSection *isec) {
+  for (Symbol *sym : isec->symbols) {
+    if (auto *d = dyn_cast_or_null<Defined>(sym)) {
+      if (!d->unwindEntry())
+        continue;
+      CompactUnwindEntry cu;
+      cu.relocateOneCompactUnwindEntry(d);
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DataCorrupted wrote:

I don't think so. Relocation seems to happen during `finalize`, way after our orderer

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