[MC] Remove MCStreamer::SymbolOrdering

21101b3 (2013) added SymbolOrdering,
which essentially became useless when
e3a20f5 (2015) removed `AssignSection`
from `EmitLabel`. `assignFragment` is still used in very few places like
emitTBSSSymbol, which do not make a difference if we remove
SymbolOrdering.

Author: MaskRay

llvm/include/llvm/MC/MCStreamer.h

@@ -228,10 +228,6 @@ class MCStreamer {
   WinEH::FrameInfo *CurrentWinFrameInfo;
   size_t CurrentProcWinFrameInfoStartIndex;
 
-  /// Tracks an index to represent the order a symbol was emitted in.
-  /// Zero means we did not emit that symbol.
-  DenseMap<const MCSymbol *, unsigned> SymbolOrdering;
-
   /// This is stack of current and previous section values saved by
   /// pushSection.
   SmallVector<std::pair<MCSectionSubPair, MCSectionSubPair>, 4> SectionStack;
@@ -416,12 +412,6 @@ class MCStreamer {
     return CurFrag;
   }
 
-  /// Returns an index to represent the order a symbol was emitted in.
-  /// (zero if we did not emit that symbol)
-  unsigned getSymbolOrder(const MCSymbol *Sym) const {
-    return SymbolOrdering.lookup(Sym);
-  }
-
   /// Save the current and previous section on the section stack.
   void pushSection() {
     SectionStack.push_back(

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -3028,20 +3028,6 @@ void DwarfDebug::emitDebugARanges() {
       continue;
     }
 
-    // Sort the symbols by offset within the section.
-    llvm::stable_sort(List, [&](const SymbolCU &A, const SymbolCU &B) {
-      unsigned IA = A.Sym ? Asm->OutStreamer->getSymbolOrder(A.Sym) : 0;
-      unsigned IB = B.Sym ? Asm->OutStreamer->getSymbolOrder(B.Sym) : 0;
-
-      // Symbols with no order assigned should be placed at the end.
-      // (e.g. section end labels)
-      if (IA == 0)
-        return false;
-      if (IB == 0)
-        return true;
-      return IA < IB;
-    });
-
     // Insert a final terminator.
     List.push_back(SymbolCU(nullptr, Asm->OutStreamer->endSection(Section)));
 

llvm/lib/MC/MCStreamer.cpp

@@ -102,7 +102,6 @@ void MCStreamer::reset() {
   DwarfFrameInfos.clear();
   CurrentWinFrameInfo = nullptr;
   WinFrameInfos.clear();
-  SymbolOrdering.clear();
   SectionStack.clear();
   SectionStack.push_back(std::pair<MCSectionSubPair, MCSectionSubPair>());
   CurFrag = nullptr;
@@ -415,10 +414,6 @@ void MCStreamer::initSections(bool NoExecStack, const MCSubtargetInfo &STI) {
 void MCStreamer::assignFragment(MCSymbol *Symbol, MCFragment *Fragment) {
   assert(Fragment);
   Symbol->setFragment(Fragment);
-
-  // As we emit symbols into a section, track the order so that they can
-  // be sorted upon later. Zero is reserved to mean 'unemitted'.
-  SymbolOrdering[Symbol] = 1 + SymbolOrdering.size();
 }
 
 void MCStreamer::emitLabel(MCSymbol *Symbol, SMLoc Loc) {