[ELF] - Detemplate BuildIdSection section.

[grimar]

Summary

Does not introduce anything new,
just performs detemplate, using methods we
already have.

[ruiu]

We are using ELFT::TargetEndianness everywhere, and this patch will change that. Doesn't this just add a different way of doing a thing that we are currently able to do? If you are going to use this in more places, please do that in this patch to demonstrate that.

[grimar]

• Changed patch to show that Config->getEndian() helps to detemplate BuildIdSection. In the same way it can be used for detemplating other places.

[grimar]

Also using getEndian for detemplating GdbIndexSection (D30976).

[ruiu]

I'm not still convinced that this is heading to the right direction. You removed a few templates in https://reviews.llvm.org/D30976, but some of them don't actually depend on this change, so they don't demonstrate how useful this change is. Can you refactor D30976 so that the patch doesn't contain unrelated de-template changes?

[grimar]

• Rebase.

[ruiu]

LGTM

ELF/SyntheticSections.h

 
 private:
   size_t NumEntries = 0;
   uint32_t TlsIndexOff = -1;
   uintX_t Size = 0;
 };
 
 // .note.gnu.build-id section.
-template <class ELFT> class BuildIdSection : public SyntheticSection {
+class BuildIdSection : public SyntheticSection {
   // First 16 bytes are a header.
   static const unsigned HeaderSize = 16;
 
 public:
   BuildIdSection();
   void writeTo(uint8_t *Buf) override;
   size_t getSize() const override { return HeaderSize + HashSize; }
   void writeBuildId(llvm::ArrayRef<uint8_t> Buf);

 SymbolBody *addSyntheticLocal(StringRef Name, uint8_t Type, uint64_t Value,
                               uint64_t Size, InputSectionBase *Section);
 
 // Linker generated sections which can be used as inputs.
 struct InX {
   static InputSection *ARMAttributes;
   static BssSection *Bss;
   static BssSection *BssRelRo;
+  static BuildIdSection *BuildId;
   static InputSection *Common;
   static StringTableSection *DynStrTab;
   static InputSection *Interp;
   static GotPltSection *GotPlt;
   static IgotPltSection *IgotPlt;
   static MipsRldMapSection *MipsRldMap;
   static PltSection *Plt;
   static PltSection *Iplt;
   static StringTableSection *ShStrTab;
   static StringTableSection *StrTab;
 };
 
 template <class ELFT> struct In : public InX {
-  static BuildIdSection<ELFT> *BuildId;
   static DynamicSection<ELFT> *Dynamic;
   static SymbolTableSection<ELFT> *DynSymTab;
   static EhFrameHeader<ELFT> *EhFrameHdr;
   static GnuHashTableSection<ELFT> *GnuHashTab;
   static GdbIndexSection<ELFT> *GdbIndex;
   static GotSection<ELFT> *Got;
   static EhFrameSection<ELFT> *EhFrame;
   static MipsGotSection<ELFT> *MipsGot;
   static HashTableSection<ELFT> *HashTab;
   static RelocationSection<ELFT> *RelaDyn;
   static RelocationSection<ELFT> *RelaPlt;
   static RelocationSection<ELFT> *RelaIplt;
   static SymbolTableSection<ELFT> *SymTab;
   static VersionDefinitionSection<ELFT> *VerDef;
   static VersionTableSection<ELFT> *VerSym;
   static VersionNeedSection<ELFT> *VerNeed;
 };
 
-template <class ELFT> BuildIdSection<ELFT> *In<ELFT>::BuildId;
 template <class ELFT> DynamicSection<ELFT> *In<ELFT>::Dynamic;
 template <class ELFT> SymbolTableSection<ELFT> *In<ELFT>::DynSymTab;
 template <class ELFT> EhFrameHeader<ELFT> *In<ELFT>::EhFrameHdr;
 template <class ELFT> GdbIndexSection<ELFT> *In<ELFT>::GdbIndex;
 template <class ELFT> GnuHashTableSection<ELFT> *In<ELFT>::GnuHashTab;
 template <class ELFT> GotSection<ELFT> *In<ELFT>::Got;
 template <class ELFT> EhFrameSection<ELFT> *In<ELFT>::EhFrame;
 template <class ELFT> MipsGotSection<ELFT> *In<ELFT>::MipsGot;

ELF/SyntheticSections.cpp

case BuildIdKind::Sha1:
     return 20;
   case BuildIdKind::Hexstring:
     return Config->BuildIdVector.size();
   default:
     llvm_unreachable("unknown BuildIdKind");
   }
 }
 
-template <class ELFT>
-BuildIdSection<ELFT>::BuildIdSection()
+BuildIdSection::BuildIdSection()
     : SyntheticSection(SHF_ALLOC, SHT_NOTE, 1, ".note.gnu.build-id"),
       HashSize(getHashSize()) {}
 
-template <class ELFT> void BuildIdSection<ELFT>::writeTo(uint8_t *Buf) {
-  const endianness E = ELFT::TargetEndianness;
-  write32<E>(Buf, 4);                   // Name size
-  write32<E>(Buf + 4, HashSize);        // Content size
-  write32<E>(Buf + 8, NT_GNU_BUILD_ID); // Type
+void BuildIdSection::writeTo(uint8_t *Buf) {
+  const endianness E = Config->IsLE ? endianness::little : endianness::big;
+  write32(Buf, 4, E);                   // Name size
+  write32(Buf + 4, HashSize, E);        // Content size
+  write32(Buf + 8, NT_GNU_BUILD_ID, E); // Type
   memcpy(Buf + 12, "GNU", 4);           // Name string
   HashBuf = Buf + 16;
 }
 
 // Split one uint8 array into small pieces of uint8 arrays.
 static std::vector<ArrayRef<uint8_t>> split(ArrayRef<uint8_t> Arr,
                                             size_t ChunkSize) {
   std::vector<ArrayRef<uint8_t>> Ret;
   while (Arr.size() > ChunkSize) {
     Ret.push_back(Arr.take_front(ChunkSize));
     Arr = Arr.drop_front(ChunkSize);
   }
   if (!Arr.empty())
     Ret.push_back(Arr);
   return Ret;
 }
 
 // Computes a hash value of Data using a given hash function.
 // In order to utilize multiple cores, we first split data into 1MB
 // chunks, compute a hash for each chunk, and then compute a hash value
 // of the hash values.
-template <class ELFT>
-void BuildIdSection<ELFT>::computeHash(
+void BuildIdSection::computeHash(
     llvm::ArrayRef<uint8_t> Data,
     std::function<void(uint8_t *Dest, ArrayRef<uint8_t> Arr)> HashFn) {
   std::vector<ArrayRef<uint8_t>> Chunks = split(Data, 1024 * 1024);
   std::vector<uint8_t> Hashes(Chunks.size() * HashSize);
 
   // Compute hash values.
   forLoop(0, Chunks.size(),
           [&](size_t I) { HashFn(Hashes.data() + I * HashSize, Chunks[I]); });
 
   // Write to the final output buffer.
   HashFn(HashBuf, Hashes);
 }
 
 BssSection::BssSection(StringRef Name)
     : SyntheticSection(SHF_ALLOC | SHF_WRITE, SHT_NOBITS, 0, Name) {}
 
 size_t BssSection::reserveSpace(uint32_t Alignment, size_t Size) {
   if (OutSec)
     OutSec->updateAlignment(Alignment);
   this->Size = alignTo(this->Size, Alignment) + Size;
   this->Alignment = std::max<uint32_t>(this->Alignment, Alignment);
   return this->Size - Size;
 }
 
-template <class ELFT>
-void BuildIdSection<ELFT>::writeBuildId(ArrayRef<uint8_t> Buf) {
+void BuildIdSection::writeBuildId(ArrayRef<uint8_t> Buf) {
   switch (Config->BuildId) {
   case BuildIdKind::Fast:
     computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {
       write64le(Dest, xxHash64(toStringRef(Arr)));
     });
     break;
   case BuildIdKind::Md5:
     computeHash(Buf, [](uint8_t *Dest, ArrayRef<uint8_t> Arr) {

 InputSection *ThunkSection::getTargetInputSection() const {
   const Thunk *T = Thunks.front();
   return T->getTargetInputSection();
 }
 
 InputSection *InX::ARMAttributes;
 BssSection *InX::Bss;
 BssSection *InX::BssRelRo;
+BuildIdSection *InX::BuildId;
 InputSection *InX::Common;
 StringTableSection *InX::DynStrTab;
 InputSection *InX::Interp;
 GotPltSection *InX::GotPlt;
 IgotPltSection *InX::IgotPlt;
 MipsRldMapSection *InX::MipsRldMap;
 PltSection *InX::Plt;
 PltSection *InX::Iplt;

 template class elf::MipsOptionsSection<ELF64LE>;
 template class elf::MipsOptionsSection<ELF64BE>;
 
 template class elf::MipsReginfoSection<ELF32LE>;
 template class elf::MipsReginfoSection<ELF32BE>;
 template class elf::MipsReginfoSection<ELF64LE>;
 template class elf::MipsReginfoSection<ELF64BE>;
 
-template class elf::BuildIdSection<ELF32LE>;
-template class elf::BuildIdSection<ELF32BE>;
-template class elf::BuildIdSection<ELF64LE>;
-template class elf::BuildIdSection<ELF64BE>;
-
 template class elf::GotSection<ELF32LE>;
 template class elf::GotSection<ELF32BE>;
 template class elf::GotSection<ELF64LE>;
 template class elf::GotSection<ELF64BE>;
 
 template class elf::MipsGotSection<ELF32LE>;
 template class elf::MipsGotSection<ELF32BE>;
 template class elf::MipsGotSection<ELF64LE>;

ELF/Writer.cpp

if (!Config->Relocatable)
     Add(createCommentSection<ELFT>());
 
   if (Config->Strip != StripPolicy::All) {
     In<ELFT>::StrTab = make<StringTableSection>(".strtab", false);
     In<ELFT>::SymTab = make<SymbolTableSection<ELFT>>(*In<ELFT>::StrTab);
   }
 
   if (Config->BuildId != BuildIdKind::None) {
-    In<ELFT>::BuildId = make<BuildIdSection<ELFT>>();
+    In<ELFT>::BuildId = make<BuildIdSection>();
     Add(In<ELFT>::BuildId);
   }
 
   In<ELFT>::Common = createCommonSection<ELFT>();
   if (In<ELFT>::Common)
     Add(InX::Common);
 
   In<ELFT>::Bss = make<BssSection>(".bss");