[yaml2obj] - Move "repeated section/fill name" check earlier.

[grimar]

Summary

This allows to simplify the code. Doing checks early is generally useful.

Needed for D80002.

Depends on D79984

[MaskRay]

LGTM.

[jhenderson]

LGTM too.

llvm/lib/ObjectYAML/ELFEmitter.cpp

ELFState<ELFT>::ELFState(ELFYAML::Object &D, yaml::ErrorHandler EH)
   // report better error messages.
   StringSet<> DocSections;
   StringRef SuffixPrefix = " [unnamed, index #";
   for (size_t I = 0; I < Doc.Chunks.size(); ++I) {
     const std::unique_ptr<ELFYAML::Chunk> &C = Doc.Chunks[I];
     if (C->Name.empty())
       C->Name = StringRef(Twine(SuffixPrefix + Twine(I) + "]").str())
                     .copy(StringAlloc);
-    DocSections.insert(C->Name);
+
+    if (!DocSections.insert(C->Name).second)
+      reportError("repeated section/fill name: '" + C->Name +
+                  "' at YAML section/fill number " + Twine(I));
   }
 
   std::vector<StringRef> ImplicitSections;
   if (Doc.DynamicSymbols)
     ImplicitSections.insert(ImplicitSections.end(), {".dynsym", ".dynstr"});
   if (Doc.Symbols)
     ImplicitSections.push_back(".symtab");
   ImplicitSections.insert(ImplicitSections.end(), {".strtab", ".shstrtab"});
void ELFState<ELFT>::writeFill(ELFYAML::Fill &Fill,
   uint64_t Written = 0;
   for (; Written + PatternSize <= Fill.Size; Written += PatternSize)
     Fill.Pattern->writeAsBinary(OS);
   Fill.Pattern->writeAsBinary(OS, Fill.Size - Written);
 }
 
 template <class ELFT> void ELFState<ELFT>::buildSectionIndex() {
   size_t SecNdx = -1;
-  StringSet<> Seen;
-  for (size_t I = 0; I < Doc.Chunks.size(); ++I) {
-    const std::unique_ptr<ELFYAML::Chunk> &C = Doc.Chunks[I];
-    bool IsSection = isa<ELFYAML::Section>(C.get());
-    if (IsSection)
-      ++SecNdx;
-
-    if (!Seen.insert(C->Name).second)
-      reportError("repeated section/fill name: '" + C->Name +
-                  "' at YAML section/fill number " + Twine(I));
-    if (!IsSection || HasError)
+  for (const std::unique_ptr<ELFYAML::Chunk> &C : Doc.Chunks) {
+    if (!isa<ELFYAML::Section>(C.get()))
       continue;
+    ++SecNdx;
 
     if (!SN2I.addName(C->Name, SecNdx))
       llvm_unreachable("buildSectionIndex() failed");
     DotShStrtab.add(ELFYAML::dropUniqueSuffix(C->Name));
   }
 
   DotShStrtab.finalize();
 }
template <class ELFT> void ELFState<ELFT>::finalizeStrings() {
 
   DotDynstr.finalize();
 }
 
 template <class ELFT>
 bool ELFState<ELFT>::writeELF(raw_ostream &OS, ELFYAML::Object &Doc,
                               yaml::ErrorHandler EH) {
   ELFState<ELFT> State(Doc, EH);
+  if (State.HasError)
+    return false;
 
   // Finalize .strtab and .dynstr sections. We do that early because want to
   // finalize the string table builders before writing the content of the
   // sections that might want to use them.
   State.finalizeStrings();
 
   State.buildSectionIndex();
-  if (State.HasError)
-    return false;
-
   State.buildSymbolIndexes();
 
   std::vector<Elf_Phdr> PHeaders;
   State.initProgramHeaders(PHeaders);
 
   // XXX: This offset is tightly coupled with the order that we write
   // things to `OS`.
   const size_t SectionContentBeginOffset =