Subzero: Track protos + globals w/out initializers as undef too (not just helper funcs)

src/IceELFObjectWriter.cpp

 //===- subzero/src/IceELFObjectWriter.cpp - ELF object file writer --------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines the writer for ELF relocatable object files.
@@ skipping 290 matching lines @@
   size_t I = 0;
   for (auto &SectionList : VarsBySection) {
     writeDataOfType(static_cast<SectionType>(I++), SectionList, RelocationKind,
                     IsELF64);
   }
 }
 
 void ELFObjectWriter::writeDataOfType(SectionType ST,
                                       const VariableDeclarationList &Vars,
                                       FixupKind RelocationKind, bool IsELF64) {
+  if (Vars.empty())
+    return;
   ELFDataSection *Section;
   ELFRelocationSection *RelSection;
   // TODO(jvoung): Handle fdata-sections.
   IceString SectionName;
-  Elf64_Xword ShAddralign = 0;
+  Elf64_Xword ShAddralign = 1;
   for (VariableDeclaration *Var : Vars) {
     Elf64_Xword Align = Var->getAlignment();
     ShAddralign = std::max(ShAddralign, Align);
   }
   const Elf64_Xword ShEntsize = 0; // non-uniform data element size.
   // Lift this out, so it can be re-used if we do fdata-sections?
   switch (ST) {
   case ROData: {
     SectionName = ".rodata";
     // Only expecting to write the data sections all in one shot for now.
@@ skipping 29 matching lines @@
     BSSSections.push_back(Section);
     break;
   }
   case NumSectionTypes:
     llvm::report_fatal_error("Unknown SectionType");
     break;
   }
 
   const uint8_t SymbolType = STT_OBJECT;
   for (VariableDeclaration *Var : Vars) {
+    // If the variable declaration does not have an initializer, its symtab
+    // entry will be created separately.
+    if (!Var->hasInitializer())
+      continue;
     Elf64_Xword Align = Var->getAlignment();
     Section->padToAlignment(Str, Align);
     SizeT SymbolSize = Var->getNumBytes();
     bool IsExternal = Var->isExternal() || Ctx.getFlags().DisableInternal;
     const uint8_t SymbolBinding = IsExternal ? STB_GLOBAL : STB_LOCAL;
     IceString MangledName = Var->mangleName(&Ctx);
     SymTab->createDefinedSym(MangledName, SymbolType, SymbolBinding, Section,
                              Section->getCurrentSize(), SymbolSize);
     StrTab->add(MangledName);
     if (!Var->hasNonzeroInitializer()) {
@@ skipping 227 matching lines @@
   if (IsELF64) {
     writeELFHeaderInternal<true>(ShOffset, ShStrTab->getNumber(),
                                  AllSections.size());
   } else {
     writeELFHeaderInternal<false>(ShOffset, ShStrTab->getNumber(),
                                   AllSections.size());
   }
 }
 
 } // end of namespace Ice