[lld] [lld-macho] icf objc stubs (PR #79730)

[Kyungwoo Lee via llvm-commits]

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@@ -332,10 +333,17 @@ class ObjCStubsSection final : public SyntheticSection {
   void setUp();
 
   static constexpr llvm::StringLiteral symbolPrefix = "_objc_msgSend$";
+  static bool isObjCStubSymbol(Symbol *sym);
+  static StringRef getMethName(Symbol *sym);
 
 private:
   std::vector<Defined *> symbols;
-  std::vector<uint32_t> offsets;
+  // Existing mapping from methname to selref (0 index is assumed).
+  llvm::StringMap<InputSection *> methnameToselref;
+  // Newly created mapping from methname to the pair of index (selref) and
+  // offset (methname).
+  llvm::MapVector<StringRef, std::pair<uint32_t, uint32_t>>
+      methnameToidxOffsetPair;
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kyulee-com wrote:

I also felt a bit awkward by having two maps, but also concerned the link time penalty as it diverged from the original implementation.
As you suggested, I came up with a single map implementation by proactively creating new selref entry when it's needed.

https://github.com/llvm/llvm-project/pull/79730