[DebugInfo] Simplify DWARFUnit::determineStringOffsetsTableContribution(). NFC.

[ikudrin]

Summary

The method is called from only one place and the call is already guarded by a condition which checks that IsDWO is false.

[jhenderson]

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

966

Perhaps it's worth asserting that IsDWO is false?

[ikudrin]

• Added assert(!IsDWO) to determineStringOffsetsTableContribution().
• Added another assert(IsDWO) to determineStringOffsetsTableContributionDWO() for the completeness.

[jhenderson]

LGTM.

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

case dwarf::DwarfFormat::DWARF32: {
     break;
   }
   }
   return Desc.validateContributionSize(DA);
 }
 
 Expected<Optional<StrOffsetsContributionDescriptor>>
 DWARFUnit::determineStringOffsetsTableContribution(DWARFDataExtractor &DA) {
-  uint64_t Offset;
-  if (IsDWO) {
-    Offset = 0;
-    if (DA.getData().data() == nullptr)
-      return None;
-  } else {
-    auto OptOffset = toSectionOffset(getUnitDIE().find(DW_AT_str_offsets_base));
-    if (!OptOffset)
-      return None;
-    Offset = *OptOffset;
-  }
-  auto DescOrError = parseDWARFStringOffsetsTableHeader(DA, Header.getFormat(), Offset);
+  assert(!IsDWO);
+  auto DescOrError =
+      parseDWARFStringOffsetsTableHeader(DA, Header.getFormat(), *OptOffset);
   if (!DescOrError)
     return DescOrError.takeError();
   return *DescOrError;
 }
 
 Expected<Optional<StrOffsetsContributionDescriptor>>
 DWARFUnit::determineStringOffsetsTableContributionDWO(DWARFDataExtractor & DA) {
+  assert(IsDWO);
   uint64_t Offset = 0;
   auto IndexEntry = Header.getIndexEntry();
   const auto *C =
       IndexEntry ? IndexEntry->getContribution(DW_SECT_STR_OFFSETS) : nullptr;
   if (C)
     Offset = C->Offset;
   if (getVersion() >= 5) {
     if (DA.getData().data() == nullptr)