Revert "Re-commit r192758 - MC: quote tricky symbol names in asm output"

This caused the clang-native-mingw32-win7 buildbot to break.

The assembler was complaining about the following lines that were showing up
in the asm for CrashRecoveryContext.cpp:

  movl  $"__ZL16ExceptionHandlerP19_EXCEPTION_POINTERS@4", 4(%eax)
  calll "_AddVectoredExceptionHandler@8"
  .def   "__ZL16ExceptionHandlerP19_EXCEPTION_POINTERS@4";
  "__ZL16ExceptionHandlerP19_EXCEPTION_POINTERS@4":
  calll "_RemoveVectoredExceptionHandler@4"

Reverting for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192940 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index 75f5c78..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('@');
+    MCSymbol *Sym = getContext().GetOrCreateSymbol(Split.first);
 
-    if (Split.first.size() != Identifier.size() &&
-        FirstTokenKind != AsmToken::String) {
-      SymbolName = Split.first;
-      StringRef VariantName = Split.second;
-
-      // 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())) {