[ELF] - Simplify removeUnusedSyntheticSections a bit.

[grimar]

Summary

Previously`InX::Got` and InX::MipsGot synthetic sections
were not removed if ElfSym::GlobalOffsetTable was defined.
ElfSym::GlobalOffsetTable is a symbol for _GLOBAL_OFFSET_TABLE_.

Patch moves ElfSym::GlobalOffsetTable check out from removeUnusedSyntheticSections.
Also note that there was no point to check ElfSym::GlobalOffsetTable for MIPS case
because InX::MipsGot::empty() always returns false for non-relocatable case, and in case
of relocatable output we do not create special symbols anyways.

[grimar]

Ping.

[ruiu]

ELF/SyntheticSections.cpp

666–668 ↗

(On Diff #114348)

Instead of adding more and more comments, you want to rewrite in most cases: We need to emit a GOT even if it's empty if there's a relocation that is relative to GOT (such as GOTOFFREL) or there's a symbol that points to a GOT (i.e. _GLOBAL_OFFSET_TABLE_).

[grimar]

• Applied suggested comment.

[ruiu]

LGTM

lld/trunk/ELF/SyntheticSections.cpp

 
 uint64_t GotSection::getGlobalDynOffset(const SymbolBody &B) const {
   return B.GlobalDynIndex * Config->Wordsize;
 }
 
 void GotSection::finalizeContents() { Size = NumEntries * Config->Wordsize; }
 
 bool GotSection::empty() const {
-  // If we have a relocation that is relative to GOT (such as GOTOFFREL),
-  // we need to emit a GOT even if it's empty.
-  return NumEntries == 0 && !HasGotOffRel;
+  // We need to emit a GOT even if it's empty if there's a relocation that is
+  // relative to GOT(such as GOTOFFREL) or there's a symbol that points to a GOT
+  // (i.e. _GLOBAL_OFFSET_TABLE_).
+  return NumEntries == 0 && !HasGotOffRel && !ElfSym::GlobalOffsetTable;
 }
 
 void GotSection::writeTo(uint8_t *Buf) {
   // Buf points to the start of this section's buffer,
   // whereas InputSectionBase::relocateAlloc() expects its argument
   // to point to the start of the output section.
   relocateAlloc(Buf - OutSecOff, Buf - OutSecOff + Size);
 }

lld/trunk/ELF/Writer.cpp

static void removeUnusedSyntheticSections() {
   // non-synthetic.
   for (InputSectionBase *S : llvm::reverse(InputSections)) {
     SyntheticSection *SS = dyn_cast<SyntheticSection>(S);
     if (!SS)
       return;
     OutputSection *OS = SS->getParent();
     if (!SS->empty() || !OS)
       continue;
-    if ((SS == InX::Got || SS == InX::MipsGot) && ElfSym::GlobalOffsetTable)
-      continue;
 
     std::vector<BaseCommand *>::iterator Empty = OS->Commands.end();
     for (auto I = OS->Commands.begin(), E = OS->Commands.end(); I != E; ++I) {
       BaseCommand *B = *I;
       if (auto *ISD = dyn_cast<InputSectionDescription>(B)) {
         llvm::erase_if(ISD->Sections,
                        [=](InputSection *IS) { return IS == SS; });
         if (ISD->Sections.empty())