[ELF] Add getOffset to ELFSectionRef and enable LLVM casting for it

[evgeny777]

Summary

Required for https://reviews.llvm.org/D26070

[ruiu]

include/llvm/Object/ELFObjectFile.h

99–101

Why do you want this?

[evgeny777]

I have Sectio

include/llvm/Object/ELFObjectFile.h

99–101

I have SectionRef object and I want to get section offset, which is ELF section property.
With this I can write:

cast<ELFSectionRef>(S)->getOffset();

Without it I have to use this one:

cast<ELFObjectFileBase>(S->getObject())->getSectionOffset(S->getRawDataRefImpl());

[• rafael]

The part adding getSectionOffset LGTM, but I agree with Rui that it is odd to have classof in only part of the hierarchy.

include/llvm/Object/ELFObjectFile.h

protected:
 
   virtual uint16_t getEMachine() const = 0;
   virtual uint64_t getSymbolSize(DataRefImpl Symb) const = 0;
   virtual uint8_t getSymbolOther(DataRefImpl Symb) const = 0;
   virtual uint8_t getSymbolELFType(DataRefImpl Symb) const = 0;
 
   virtual uint32_t getSectionType(DataRefImpl Sec) const = 0;
   virtual uint64_t getSectionFlags(DataRefImpl Sec) const = 0;
+  virtual uint64_t getSectionOffset(DataRefImpl Sec) const = 0;
 
   virtual ErrorOr<int64_t> getRelocationAddend(DataRefImpl Rel) const = 0;
 
 public:
   typedef iterator_range<elf_symbol_iterator> elf_symbol_iterator_range;
   virtual elf_symbol_iterator_range getDynamicSymbolIterators() const = 0;
 
   elf_symbol_iterator_range symbols() const;
public:
 
   uint32_t getType() const {
     return getObject()->getSectionType(getRawDataRefImpl());
   }
 
   uint64_t getFlags() const {
     return getObject()->getSectionFlags(getRawDataRefImpl());
   }
+
+  uint64_t getOffset() const {
+    return getObject()->getSectionOffset(getRawDataRefImpl());
+  }
+
+  static inline bool classof(const SectionRef *v) {
+    return v->getObject()->isELF();
+  }
 };
 
 class elf_section_iterator : public section_iterator {
 public:
   elf_section_iterator(const section_iterator &B) : section_iterator(B) {
     assert(isa<ELFObjectFileBase>(B->getObject()));
   }
 
protected:
   uint64_t getRelocationOffset(DataRefImpl Rel) const override;
   symbol_iterator getRelocationSymbol(DataRefImpl Rel) const override;
   uint64_t getRelocationType(DataRefImpl Rel) const override;
   void getRelocationTypeName(DataRefImpl Rel,
                              SmallVectorImpl<char> &Result) const override;
 
   uint32_t getSectionType(DataRefImpl Sec) const override;
   uint64_t getSectionFlags(DataRefImpl Sec) const override;
+  uint64_t getSectionOffset(DataRefImpl Sec) const override;
   StringRef getRelocationTypeName(uint32_t Type) const;
 
   /// \brief Get the relocation section that contains \a Rel.
   const Elf_Shdr *getRelSection(DataRefImpl Rel) const {
     return *EF.getSection(Rel.d.a);
   }
 
   DataRefImpl toDRI(const Elf_Shdr *SymTable, unsigned SymbolNum) const {

 }
 
 template <class ELFT>
 uint32_t ELFObjectFile<ELFT>::getSectionType(DataRefImpl Sec) const {
   return getSection(Sec)->sh_type;
 }
 
 template <class ELFT>
+uint64_t ELFObjectFile<ELFT>::getSectionOffset(DataRefImpl Sec) const {
+  return getSection(Sec)->sh_offset;
+}
+
+template <class ELFT>
 uint64_t ELFObjectFile<ELFT>::getSymbolValueImpl(DataRefImpl Symb) const {
   const Elf_Sym *ESym = getSymbol(Symb);
   uint64_t Ret = ESym->st_value;
   if (ESym->st_shndx == ELF::SHN_ABS)
     return Ret;
 
   const Elf_Ehdr *Header = EF.getHeader();
   // Clear the ARM/Thumb or microMIPS indicator flag.