[clang] [lld] [llvm] [LTO][LLD] Prevent invalid LTO libfunc transforms (PR #164916)

[Matt Arsenault via cfe-commits]

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@@ -443,6 +450,14 @@ class LTO {
   LLVM_ABI static SmallVector<const char *>
   getRuntimeLibcallSymbols(const Triple &TT);
 
+  /// Static method that returns a list of library function symbols that can be
+  /// generated by LTO but might not be visible from bitcode symbol table.
+  /// Unlike the runtime libcalls, the linker can report to the code generator
+  /// which of these are actually available in the link, and the code generator
+  /// can then only reference that set of symbols.
+  LLVM_ABI static SmallVector<StringRef>
+  getLibFuncSymbols(const Triple &TT, llvm::StringSaver &Saver);
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arsenm wrote:

With this, the linker needs to take the set of symbols from both here and getRuntimeLibcallSymbols? I guess that makes sense, but is even more reason that these should be fused 

https://github.com/llvm/llvm-project/pull/164916