[ELF] - Reset output section size when assigning offsets.

In many places we reset Size to 0 before calling assignOffsets()
manually. Sometimes we don't do that. 
It looks we can just always do that inside.

Previous code had:
template <class ELFT> void OutputSection::assignOffsets() {
  uint64_t Off = Size;

And tests feels fine with Off = 0. 
I think Off = Size make no sence.

Differential revision: https://reviews.llvm.org/D30463

llvm-svn: 296609

lld/ELF/OutputSections.cpp

@@ -87,7 +87,6 @@ static bool compareByFilePosition(InputSection *A, InputSection *B) {
 template <class ELFT> void OutputSection::finalize() {
   if ((this->Flags & SHF_LINK_ORDER) && !this->Sections.empty()) {
     std::sort(Sections.begin(), Sections.end(), compareByFilePosition<ELFT>);
-    Size = 0;
     assignOffsets<ELFT>();
 
     // We must preserve the link order dependency of sections with the
@@ -133,7 +132,7 @@ void OutputSection::addSection(InputSectionBase *C) {
 // This function is called after we sort input sections
 // and scan relocations to setup sections' offsets.
 template <class ELFT> void OutputSection::assignOffsets() {
-  uint64_t Off = this->Size;
+  uint64_t Off = 0;
   for (InputSection *S : Sections) {
     Off = alignTo(Off, S->Alignment);
     S->OutSecOff = Off;

lld/ELF/Relocations.cpp

@@ -886,7 +886,6 @@ static void mergeThunks(OutputSection *OS,
   std::merge(OS->Sections.begin(), OS->Sections.end(), Thunks.begin(),
              Thunks.end(), std::back_inserter(Tmp), MergeCmp);
   OS->Sections = std::move(Tmp);
-  OS->Size = 0;
   OS->assignOffsets<ELFT>();
 }
 

lld/ELF/Writer.cpp

@@ -1025,7 +1025,6 @@ static void finalizeSynthetic(const std::vector<SyntheticSection *> &Sections) {
   for (SyntheticSection *SS : Sections)
     if (SS && SS->OutSec && !SS->empty()) {
       SS->finalizeContents();
-      SS->OutSec->Size = 0;
       SS->OutSec->template assignOffsets<ELFT>();
     }
 }