Revert r192758 (and r192759), "MC: Better handling of tricky symbol and section names"

GNU AS didn't like quotes in symbol names.

    Error: junk at end of line, first unrecognized character is `"'

        .def "@feat.00";
        "@feat.00" = 1

Reproduced on Cygwin's 2.23.52.20130309 and mingw32's 2.20.1.20100303.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192775 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index 50fe415..9a36256 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -792,25 +792,19 @@
     EndLoc = SMLoc::getFromPointer(Identifier.end());
 
     // This is a symbol reference.
-    StringRef SymbolName = Identifier;
-    MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
     std::pair<StringRef, StringRef> Split = Identifier.split('@');
-    
-    if (Split.first.size() != Identifier.size() &&
-        FirstTokenKind != AsmToken::String) {
-      SymbolName = Split.first;
-      StringRef VariantName = Split.second;
+    MCSymbol *Sym = getContext().GetOrCreateSymbol(Split.first);
 
-      // Lookup the symbol variant.
-      Variant = MCSymbolRefExpr::getVariantKindForName(VariantName);
+    // Lookup the symbol variant if used.
+    MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
+    if (Split.first.size() != Identifier.size()) {
+      Variant = MCSymbolRefExpr::getVariantKindForName(Split.second);
       if (Variant == MCSymbolRefExpr::VK_Invalid) {
         Variant = MCSymbolRefExpr::VK_None;
-        return TokError("invalid variant '" + VariantName + "'");
+        return TokError("invalid variant '" + Split.second + "'");
       }
     }
 
-    MCSymbol *Sym = getContext().GetOrCreateSymbol(SymbolName);
-
     // If this is an absolute variable reference, substitute it now to preserve
     // semantics in the face of reassignment.
     if (Sym->isVariable() && isa<MCConstantExpr>(Sym->getVariableValue())) {