[lld] [ELF] [MIPS] Remove duplicate logic

[rafaelauler]

Summary

With r218633, the logic that monitors which shared library symbols were used was copied from the MIPS lld backend to ELF classes, making it available to all ELF backends. However, this made the isDynSymEntryRequired() functions in MipsDynamicLibraryWriter.h/MipsELFWriters.h/MipsExecutableWriter.h to be duplicated logic, since this is already implemented in OutputELFWriter<>/DefaultLayout. This patch removes this duplicated code from MIPS.

[rafaelauler]

Committed r218846.

lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h

protected:
   void finalizeDefaultAtomValues() override;
 
   std::error_code setELFHeader() override {
     DynamicLibraryWriter<ELFT>::setELFHeader();
     _writeHelper.setELFHeader(*this->_elfHeader);
     return std::error_code();
   }
 
-  bool isDynSymEntryRequired(const SharedLibraryAtom *sla) const override {
-    return _writeHelper.isDynSymEntryRequired(sla);
-  }
-
   bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
     return _writeHelper.isNeededTagRequired(sla);
   }
 
   LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
 
   LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();
 

lib/ReaderWriter/ELF/Mips/MipsELFWriters.h

if (_ctx.isDynamic()) {
       file->addAbsoluteAtom("_GLOBAL_OFFSET_TABLE_");
       file->addAbsoluteAtom("_gp");
       file->addAbsoluteAtom("_gp_disp");
       file->addAbsoluteAtom("__gnu_local_gp");
     }
     return file;
   }
 
-  bool isDynSymEntryRequired(const SharedLibraryAtom *sla) const {
-    return _targetLayout.isReferencedByDefinedAtom(sla);
-  }
-
   bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
     return _targetLayout.isReferencedByDefinedAtom(sla) ||
            _targetLayout.isCopied(sla);
   }
 
 private:
   MipsLinkingContext &_ctx;
   MipsTargetLayout<ELFT> &_targetLayout;

lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h

protected:
   void finalizeDefaultAtomValues() override;
 
   std::error_code setELFHeader() override {
     ExecutableWriter<ELFT>::setELFHeader();
     _writeHelper.setELFHeader(*this->_elfHeader);
     return std::error_code();
   }
 
-  bool isDynSymEntryRequired(const SharedLibraryAtom *sla) const override {
-    return _writeHelper.isDynSymEntryRequired(sla);
-  }
-
   bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
     return _writeHelper.isNeededTagRequired(sla);
   }
 
   LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
 
   LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();