[llvm-objcopy] - Remove dead code. NFCI.

[grimar]

Summary

DecompressedSection can only be created if --decompress-debug-sections is specified.
https://github.com/llvm-mirror/llvm/blob/master/tools/llvm-objcopy/ELF/ELFObjcopy.cpp#L492

If it is specified when !zlib::isAvailable(), we error out early when parsing the options:
https://github.com/llvm-mirror/llvm/blob/master/tools/llvm-objcopy/CopyConfig.cpp#L657

What means the code I am removing in this patch is dead.

[jhenderson]

LGTM.

[jhenderson]

tools/llvm-objcopy/ELF/Object.cpp

184

I wonder if it's worth making zlib::isAvailable() an assertion in this function?

[grimar]

tools/llvm-objcopy/ELF/Object.cpp

184

I think it might be better to have an assert in DecompressedSection's constructor then.
This section is not expected to be created in case of !zlib::isAvailable() first of all.

[jhenderson]

tools/llvm-objcopy/ELF/Object.cpp

184

Actually, it's moot, since there is an llvm_unreachable assertion in zlib::uncompress is called when it isn't available, so no need for the assertion at all, I think, although it doesn't hurt to have one in the constructor if you want to add it.

tools/llvm-objcopy/ELF/Object.cpp

const uint64_t DecompressedAlign =
       IsGnuDebug ? 1
                  : reinterpret_cast<const Elf_Chdr_Impl<ELFT> *>(Data.data())
                        ->ch_addralign;
 
   return std::make_tuple(DecompressedSize, DecompressedAlign);
 }
 
 template <class ELFT>
 void ELFSectionWriter<ELFT>::visit(const DecompressedSection &Sec) {
-  uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
-
-  if (!zlib::isAvailable()) {
-    std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), Buf);
-    return;
-  }
-
   const size_t DataOffset = isDataGnuCompressed(Sec.OriginalData)
                                 ? (ZlibGnuMagic.size() + sizeof(Sec.Size))
                                 : sizeof(Elf_Chdr_Impl<ELFT>);
 
   StringRef CompressedContent(
       reinterpret_cast<const char *>(Sec.OriginalData.data()) + DataOffset,
       Sec.OriginalData.size() - DataOffset);
 
   SmallVector<char, 128> DecompressedContent;
   if (Error E = zlib::uncompress(CompressedContent, DecompressedContent,
                                  static_cast<size_t>(Sec.Size)))
     reportError(Sec.Name, std::move(E));
 
+  uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
   std::copy(DecompressedContent.begin(), DecompressedContent.end(), Buf);
 }
 
 void BinarySectionWriter::visit(const DecompressedSection &Sec) {
   error("Cannot write compressed section '" + Sec.Name + "' ");
 }
 
 void DecompressedSection::accept(SectionVisitor &Visitor) const {