[ELF] - Refactor of Writer<ELFT>::forEachRelSec.

[grimar]

Summary

There is no need to scan over all input sections for relocatable output.
As we do not process or scan relocations anyways.
Patch moves check for Config->Relocatable out to avoid that and also removes
excessive check for isa<EhInputSection> from first for loop.
It is excessive because we handle all of them in a second for loop below.
That all allowed to simplify code.

[ruiu]

LGTM

lld/trunk/ELF/Writer.cpp

template <class ELFT> static void sortBySymbolsOrder() {
   DenseMap<SectionBase *, int> SectionOrder = buildSectionOrder<ELFT>();
   for (BaseCommand *Base : Script->Opt.Commands)
     if (auto *Sec = dyn_cast<OutputSection>(Base))
       Sec->sort([&](InputSectionBase *S) { return SectionOrder.lookup(S); });
 }
 
 template <class ELFT>
 void Writer<ELFT>::forEachRelSec(std::function<void(InputSectionBase &)> Fn) {
-  for (InputSectionBase *IS : InputSections) {
-    if (!IS->Live)
-      continue;
-    // Scan all relocations. Each relocation goes through a series
-    // of tests to determine if it needs special treatment, such as
-    // creating GOT, PLT, copy relocations, etc.
-    // Note that relocations for non-alloc sections are directly
-    // processed by InputSection::relocateNonAlloc.
-    if (!(IS->Flags & SHF_ALLOC))
-      continue;
-    if (isa<InputSection>(IS) || isa<EhInputSection>(IS))
+  for (InputSectionBase *IS : InputSections)
+    if (IS->Live && isa<InputSection>(IS) && (IS->Flags & SHF_ALLOC))
       Fn(*IS);
-  }
-
-  if (!Config->Relocatable) {
-    for (EhInputSection *ES : In<ELFT>::EhFrame->Sections)
-      Fn(*ES);
-  }
-}
 
 template <class ELFT> void Writer<ELFT>::createSections() {
   std::vector<BaseCommand *> Old = Script->Opt.Commands;
   Script->Opt.Commands.clear();
   for (InputSectionBase *IS : InputSections)
     if (IS)
       Factory.addInputSec(IS, getOutputSectionName(IS->Name));
   Script->Opt.Commands.insert(Script->Opt.Commands.end(), Old.begin(),
template <class ELFT> void Writer<ELFT>::finalizeSections() {
   applySynthetic({In<ELFT>::EhFrame},
                  [](SyntheticSection *SS) { SS->finalizeContents(); });
 
   for (Symbol *S : Symtab->getSymbols())
     S->body()->IsPreemptible |= computeIsPreemptible(*S->body());
 
   // Scan relocations. This must be done after every symbol is declared so that
   // we can correctly decide if a dynamic relocation is needed.
+  if (!Config->Relocatable)
     forEachRelSec(scanRelocations<ELFT>);
 
   if (InX::Plt && !InX::Plt->empty())
     InX::Plt->addSymbols();
   if (InX::Iplt && !InX::Iplt->empty())
     InX::Iplt->addSymbols();
 
   // Now that we have defined all possible global symbols including linker-
   // synthesized ones. Visit all symbols to give the finishing touches.