Revert r240302 ("Bring r240130 back.").

This causes errors like:

  ld: error: blah.o: requires dynamic R_X86_64_PC32 reloc against '' which
  may overflow at runtime; recompile with -fPIC
  blah.cc:function f(): error: undefined reference to ''
  blah.o:g(): error: undefined reference to ''

I have not yet come up with an appropriate reproduction.

llvm-svn: 240394

3 files changed, 19 insertions, 25 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 71d3f86d9e6..db9c759f2b5 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -787,15 +787,10 @@ void ELFObjectWriter::computeSymbolTable(
                     Renames.count(&Symbol)))
       continue;
 
-    if (Symbol.isTemporary() && Symbol.isUndefined())
-      Ctx.reportFatalError(SMLoc(), "Undefined temporary");
-
     ELFSymbolData MSD;
     MSD.Symbol = cast<MCSymbolELF>(&Symbol);
 
     bool Local = Symbol.getBinding() == ELF::STB_LOCAL;
-    assert(Local || !Symbol.isTemporary());
-
     if (Symbol.isAbsolute()) {
       MSD.SectionIndex = ELF::SHN_ABS;
     } else if (Symbol.isCommon()) {
@@ -894,11 +889,9 @@ void ELFObjectWriter::computeSymbolTable(
   unsigned Index = FileNames.size() + 1;
 
   for (ELFSymbolData &MSD : LocalSymbolData) {
-    unsigned StringIndex;
-    if (MSD.Symbol->getType() == ELF::STT_SECTION || MSD.Name.empty())
-      StringIndex = 0;
-    else
-      StringIndex = StrTabBuilder.getOffset(MSD.Name);
+    unsigned StringIndex = MSD.Symbol->getType() == ELF::STT_SECTION
+                               ? 0
+                               : StrTabBuilder.getOffset(MSD.Name);
     MSD.Symbol->setIndex(Index++);
     writeSymbol(Writer, StringIndex, MSD, Layout);
   }
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 01074eb5e79..c601c56f395 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -116,7 +116,7 @@ MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
 
   MCSymbol *&Sym = Symbols[NameRef];
   if (!Sym)
-    Sym = createSymbol(NameRef, false);
+    Sym = createSymbol(NameRef, false, false);
 
   return Sym;
 }
@@ -175,16 +175,17 @@ MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
                                     IsTemporary);
 }
 
-MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix) {
+MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
+                                  bool CanBeUnnamed) {
+  if (CanBeUnnamed && !UseNamesOnTempLabels)
+    return createSymbolImpl(nullptr, true);
+
   // Determine whether this is an user writter assembler temporary or normal
   // label, if used.
-  bool IsTemporary = false;
-  if (AllowTemporaryLabels)
+  bool IsTemporary = CanBeUnnamed;
+  if (AllowTemporaryLabels && !IsTemporary)
     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
 
-  if (IsTemporary && !UseNamesOnTempLabels)
-    return createSymbolImpl(nullptr, true);
-
   SmallString<128> NewName = Name;
   bool AddSuffix = AlwaysAddSuffix;
   unsigned &NextUniqueID = NextID[Name];
@@ -205,20 +206,21 @@ MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix) {
   llvm_unreachable("Infinite loop");
 }
 
-MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix) {
+MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
+                                      bool CanBeUnnamed) {
   SmallString<128> NameSV;
   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
-  return createSymbol(NameSV, AlwaysAddSuffix);
+  return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
 }
 
 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
   SmallString<128> NameSV;
   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
-  return createSymbol(NameSV, true);
+  return createSymbol(NameSV, true, false);
 }
 
-MCSymbol *MCContext::createTempSymbol() {
-  return createTempSymbol("tmp", true);
+MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
+  return createTempSymbol("tmp", true, CanBeUnnamed);
 }
 
 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
@@ -239,7 +241,7 @@ MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
                                                        unsigned Instance) {
   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
   if (!Sym)
-    Sym = createTempSymbol();
+    Sym = createTempSymbol(false);
   return Sym;
 }
 
diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index d7934ad80c6..8ce6127e386 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -565,8 +565,7 @@ void MachObjectWriter::computeSymbolTable(
 
     MachSymbolData MSD;
     MSD.Symbol = &Symbol;
-    StringRef Name = Symbol.getName();
-    MSD.StringIndex = Name.empty() ? 0 : StringTable.getOffset(Name);
+    MSD.StringIndex = StringTable.getOffset(Symbol.getName());
 
     if (Symbol.isAbsolute()) {
       MSD.SectionIndex = 0;