Revert commit r219835 and r219829.

Revert "Correctly handle references to section symbols."
Revert "Allow forward references to section symbols."

Rui found a regression I am debugging.

llvm-svn: 220010

3 files changed, 50 insertions, 61 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index d77f03f5281..4577f0130ed 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -81,13 +81,23 @@ public:
 
 struct ELFRelocationEntry {
   uint64_t Offset; // Where is the relocation.
-  const MCSymbol *Symbol;       // The symbol to relocate with.
+  bool UseSymbol;  // Relocate with a symbol, not the section.
+  union {
+    const MCSymbol *Symbol;       // The symbol to relocate with.
+    const MCSectionData *Section; // The section to relocate with.
+  };
   unsigned Type;   // The type of the relocation.
   uint64_t Addend; // The addend to use.
 
   ELFRelocationEntry(uint64_t Offset, const MCSymbol *Symbol, unsigned Type,
                      uint64_t Addend)
-      : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend) {}
+      : Offset(Offset), UseSymbol(true), Symbol(Symbol), Type(Type),
+        Addend(Addend) {}
+
+  ELFRelocationEntry(uint64_t Offset, const MCSectionData *Section,
+                     unsigned Type, uint64_t Addend)
+      : Offset(Offset), UseSymbol(false), Section(Section), Type(Type),
+        Addend(Addend) {}
 };
 
 class ELFObjectWriter : public MCObjectWriter {
@@ -127,14 +137,6 @@ class ELFObjectWriter : public MCObjectWriter {
 
       // Support lexicographic sorting.
       bool operator<(const ELFSymbolData &RHS) const {
-        unsigned LHSType = MCELF::GetType(*SymbolData);
-        unsigned RHSType = MCELF::GetType(*RHS.SymbolData);
-        if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
-          return false;
-        if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
-          return true;
-        if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
-          return SectionIndex < RHS.SectionIndex;
         return Name < RHS.Name;
       }
     };
@@ -649,6 +651,22 @@ void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
     WriteSymbol(Writer, MSD, Layout);
   }
 
+  // Write out a symbol table entry for each regular section.
+  for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
+       ++i) {
+    const MCSectionELF &Section =
+      static_cast<const MCSectionELF&>(i->getSection());
+    if (Section.getType() == ELF::SHT_RELA ||
+        Section.getType() == ELF::SHT_REL ||
+        Section.getType() == ELF::SHT_STRTAB ||
+        Section.getType() == ELF::SHT_SYMTAB ||
+        Section.getType() == ELF::SHT_SYMTAB_SHNDX)
+      continue;
+    Writer.writeSymbol(0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT,
+                       SectionIndexMap.lookup(&Section), false);
+    LastLocalSymbolIndex++;
+  }
+
   for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
     ELFSymbolData &MSD = ExternalSymbolData[i];
     MCSymbolData &Data = *MSD.SymbolData;
@@ -864,11 +882,8 @@ void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
   if (!RelocateWithSymbol) {
     const MCSection *SecA =
         (SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr;
-    auto *ELFSec = cast_or_null<MCSectionELF>(SecA);
-    MCSymbol *SectionSymbol =
-        ELFSec ? Asm.getContext().GetOrCreateSymbol(ELFSec->getSectionName())
-               : nullptr;
-    ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend);
+    const MCSectionData *SecAD = SecA ? &Asm.getSectionData(*SecA) : nullptr;
+    ELFRelocationEntry Rec(FixupOffset, SecAD, Type, Addend);
     Relocations[FixupSection].push_back(Rec);
     return;
   }
@@ -1046,10 +1061,7 @@ ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
       Buf += Name.substr(Pos + Skip);
       Name = Buf;
     }
-
-    // Sections have their own string table
-    if (MCELF::GetType(SD) != ELF::STT_SECTION)
-      MSD.Name = StrTabBuilder.add(Name);
+    MSD.Name = StrTabBuilder.add(Name);
 
     if (MSD.SectionIndex == ELF::SHN_UNDEF)
       UndefinedSymbolData.push_back(MSD);
@@ -1067,11 +1079,9 @@ ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
   for (auto i = Asm.file_names_begin(), e = Asm.file_names_end(); i != e; ++i)
     FileSymbolData.push_back(StrTabBuilder.getOffset(*i));
 
-  for (ELFSymbolData &MSD : LocalSymbolData)
-    MSD.StringIndex = MCELF::GetType(*MSD.SymbolData) == ELF::STT_SECTION
-                          ? 0
-                          : StrTabBuilder.getOffset(MSD.Name);
-  for (ELFSymbolData &MSD : ExternalSymbolData)
+  for (ELFSymbolData& MSD : LocalSymbolData)
+    MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name);
+  for (ELFSymbolData& MSD : ExternalSymbolData)
     MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name);
   for (ELFSymbolData& MSD : UndefinedSymbolData)
     MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name);
@@ -1087,6 +1097,8 @@ ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
   for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
     LocalSymbolData[i].SymbolData->setIndex(Index++);
 
+  Index += NumRegularSections;
+
   for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
     ExternalSymbolData[i].SymbolData->setIndex(Index++);
   for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
@@ -1342,8 +1354,18 @@ void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
 
   for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
     const ELFRelocationEntry &Entry = Relocs[e - i - 1];
-    unsigned Index =
-        Entry.Symbol ? getSymbolIndexInSymbolTable(Asm, Entry.Symbol) : 0;
+
+    unsigned Index;
+    if (Entry.UseSymbol) {
+      Index = getSymbolIndexInSymbolTable(Asm, Entry.Symbol);
+    } else {
+      const MCSectionData *Sec = Entry.Section;
+      if (Sec)
+        Index = Sec->getOrdinal() + FileSymbolData.size() +
+                LocalSymbolData.size() + 1;
+      else
+        Index = 0;
+    }
 
     if (is64Bit()) {
       write(*F, Entry.Offset);
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index ea6db142fd7..9d8a57e55f6 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -113,30 +113,6 @@ MCSymbol *MCContext::GetOrCreateSymbol(StringRef Name) {
   return Sym;
 }
 
-MCSymbol *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
-  MCSymbol *&Sym = SectionSymbols[&Section];
-  if (Sym)
-    return Sym;
-
-  StringRef Name = Section.getSectionName();
-
-  StringMapEntry<MCSymbol*> &Entry = Symbols.GetOrCreateValue(Name);
-  MCSymbol *OldSym = Entry.getValue();
-  if (OldSym && OldSym->isUndefined()) {
-    Sym = OldSym;
-    return OldSym;
-  }
-
-  StringMapEntry<bool> *NameEntry = &UsedNames.GetOrCreateValue(Name);
-  NameEntry->setValue(true);
-  Sym = new (*this) MCSymbol(NameEntry->getKey(), /*isTemporary*/ false);
-
-  if (!Entry.getValue())
-    Entry.setValue(Sym);
-
-  return Sym;
-}
-
 MCSymbol *MCContext::CreateSymbol(StringRef Name) {
   // Determine whether this is an assembler temporary or normal label, if used.
   bool isTemporary = false;
diff --git a/llvm/lib/MC/MCELFStreamer.cpp b/llvm/lib/MC/MCELFStreamer.cpp
index bdc4a8410fb..4ef22d00224 100644
--- a/llvm/lib/MC/MCELFStreamer.cpp
+++ b/llvm/lib/MC/MCELFStreamer.cpp
@@ -92,19 +92,10 @@ void MCELFStreamer::ChangeSection(const MCSection *Section,
   MCSectionData *CurSection = getCurrentSectionData();
   if (CurSection && CurSection->isBundleLocked())
     report_fatal_error("Unterminated .bundle_lock when changing a section");
-
-  MCAssembler &Asm = getAssembler();
-  auto *SectionELF = static_cast<const MCSectionELF *>(Section);
-  const MCSymbol *Grp = SectionELF->getGroup();
+  const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
   if (Grp)
-    Asm.getOrCreateSymbolData(*Grp);
-
+    getAssembler().getOrCreateSymbolData(*Grp);
   this->MCObjectStreamer::ChangeSection(Section, Subsection);
-  MCSymbol *SectionSymbol = getContext().getOrCreateSectionSymbol(*SectionELF);
-  if (SectionSymbol->isUndefined()) {
-    EmitLabel(SectionSymbol);
-    MCELF::SetType(Asm.getSymbolData(*SectionSymbol), ELF::STT_SECTION);
-  }
 }
 
 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {