[lld-macho][nfc] Hoist out creation of Section in parseSections()

[int3]

Summary

Simplifies the code slightly.

[thakis]

lgtm

lld/MachO/InputFiles.cpp

void ObjFile::parseSections(ArrayRef<SectionHeader> sectionHeaders) {
   for (const SectionHeader &sec : sectionHeaders) {
     StringRef name =
         StringRef(sec.sectname, strnlen(sec.sectname, sizeof(sec.sectname)));
     StringRef segname =
         StringRef(sec.segname, strnlen(sec.segname, sizeof(sec.segname)));
     ArrayRef<uint8_t> data = {isZeroFill(sec.flags) ? nullptr
                                                     : buf + sec.offset,
                               static_cast<size_t>(sec.size)};
+    sections.push_back(sec.addr);
     if (sec.align >= 32) {
       error("alignment " + std::to_string(sec.align) + " of section " + name +
             " is too large");
-      sections.push_back(sec.addr);
       continue;
     }
     uint32_t align = 1 << sec.align;
     uint32_t flags = sec.flags;
 
     auto splitRecords = [&](int recordSize) -> void {
-      sections.push_back(sec.addr);
       if (data.empty())
         return;
       Subsections &subsections = sections.back().subsections;
       subsections.reserve(data.size() / recordSize);
       auto *isec = make<ConcatInputSection>(
           segname, name, this, data.slice(0, recordSize), align, flags);
       subsections.push_back({0, isec});
       for (uint64_t off = recordSize; off < data.size(); off += recordSize) {
if (sectionType(sec.flags) == S_CSTRING_LITERALS ||
         isec =
             make<CStringInputSection>(segname, name, this, data, align, flags);
         // FIXME: parallelize this?
         cast<CStringInputSection>(isec)->splitIntoPieces();
       } else {
         isec = make<WordLiteralInputSection>(segname, name, this, data, align,
                                              flags);
       }
-      sections.push_back(sec.addr);
       sections.back().subsections.push_back({0, isec});
     } else if (auto recordSize = getRecordSize(segname, name)) {
       splitRecords(*recordSize);
       if (name == section_names::compactUnwind)
         compactUnwindSection = &sections.back();
     } else if (segname == segment_names::llvm) {
       if (name == "__cg_profile" && config->callGraphProfileSort) {
         TimeTraceScope timeScope("Parsing call graph section");
if (sectionType(sec.flags) == S_CSTRING_LITERALS ||
           entry.fromIndex = fromIndex;
           entry.toIndex = toIndex;
           entry.count = count;
         }
       }
       // ld64 does not appear to emit contents from sections within the __LLVM
       // segment. Symbols within those sections point to bitcode metadata
       // instead of actual symbols. Global symbols within those sections could
-      // have the same name without causing duplicate symbol errors. Push an
-      // empty entry to ensure indices line up for the remaining sections.
+      // have the same name without causing duplicate symbol errors. To avoid
+      // spurious duplicate symbol errors, we do not parse these sections.
       // TODO: Evaluate whether the bitcode metadata is needed.
-      sections.push_back(sec.addr);
     } else {
       auto *isec =
           make<ConcatInputSection>(segname, name, this, data, align, flags);
       if (isDebugSection(isec->getFlags()) &&
           isec->getSegName() == segment_names::dwarf) {
         // Instead of emitting DWARF sections, we emit STABS symbols to the
         // object files that contain them. We filter them out early to avoid
-        // parsing their relocations unnecessarily. But we must still push an
-        // empty entry to ensure the indices line up for the remaining sections.
-        sections.push_back(sec.addr);
+        // parsing their relocations unnecessarily.
         debugSections.push_back(isec);
       } else {
-        sections.push_back(sec.addr);
         sections.back().subsections.push_back({0, isec});
       }
     }
   }
 }
 
 // Find the subsection corresponding to the greatest section offset that is <=
 // that of the given offset.