libObject: add a function to get pointers to relocation table entries

[ruiu]

Summary

I need this function for LLD.

[majnemer]

LGTM

[Eugene.Zelenko]

Committed in r240610.

include/llvm/Object/COFF.h

public:
   size_t getSymbolTableEntrySize() const {
     if (COFFHeader)
       return sizeof(coff_symbol16);
     if (COFFBigObjHeader)
       return sizeof(coff_symbol32);
     llvm_unreachable("null symbol table pointer!");
   }
 
+  iterator_range<const coff_relocation *>
+  getRelocations(const coff_section *Sec) const;
+
   std::error_code getSectionName(const coff_section *Sec, StringRef &Res) const;
   uint64_t getSectionSize(const coff_section *Sec) const;
   std::error_code getSectionContents(const coff_section *Sec,
                                      ArrayRef<uint8_t> &Res) const;
 
   std::error_code getVaPtr(uint64_t VA, uintptr_t &Res) const;
   std::error_code getRvaPtr(uint32_t Rva, uintptr_t &Res) const;
   std::error_code getHintName(uint32_t Rva, uint16_t &Hint,

lib/Object/COFFObjectFile.cpp

 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Object/COFF.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/COFF.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cctype>
 #include <limits>
 
 using namespace llvm;
 using namespace object;
COFFSymbolRef COFFObjectFile::getCOFFSymbol(const SymbolRef &Symbol) const {
   return getCOFFSymbol(Symbol.getRawDataRefImpl());
 }
 
 const coff_relocation *
 COFFObjectFile::getCOFFRelocation(const RelocationRef &Reloc) const {
   return toRel(Reloc.getRawDataRefImpl());
 }
 
+iterator_range<const coff_relocation *>
+COFFObjectFile::getRelocations(const coff_section *Sec) const {
+  const coff_relocation *I = getFirstReloc(Sec, Data, base());
+  const coff_relocation *E = I;
+  if (I)
+    E += getNumberOfRelocations(Sec, Data, base());
+  return make_range(I, E);
+}
+
 #define LLVM_COFF_SWITCH_RELOC_TYPE_NAME(reloc_type)                           \
   case COFF::reloc_type:                                                       \
     Res = #reloc_type;                                                         \
     break;
 
 std::error_code
 COFFObjectFile::getRelocationTypeName(DataRefImpl Rel,
                                       SmallVectorImpl<char> &Result) const {