[llvm] [CodeGen][Transforms] Remove unused DenseMapInfo::getEmptyKey (PR #201994)

[Fangrui Song via llvm-commits]

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@@ -1819,13 +1819,10 @@ std::vector<Chain> Vectorizer::gatherChains(ArrayRef<Instruction *> Instrs) {
   struct InstrListElemDenseMapInfo {
     using PtrInfo = DenseMapInfo<InstrListElem *>;
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MaskRay wrote:

removed

https://github.com/llvm/llvm-project/pull/201994