[X86][ms-inline asm] Add support for memory operands that include structs

[myatsina]

Summary

Add ability to reference struct symbols in memory operands.
Test case will be added on the clang side.

[myatsina]

Test case review on clang side:
http://reviews.llvm.org/D15749

[mcrosier]

LGTM.

llvm/trunk/lib/Target/X86/AsmParser/X86AsmParser.cpp

if (unsigned Len = End.getPointer() - (SymLocPtr + SymName.size())) {
     AsmRewrites.emplace_back(AOK_Skip, Loc, Len);
   }
 }
 
 bool X86AsmParser::ParseIntelExpression(IntelExprStateMachine &SM, SMLoc &End) {
   MCAsmParser &Parser = getParser();
   const AsmToken &Tok = Parser.getTok();
 
+  AsmToken::TokenKind PrevTK = AsmToken::Error;
   bool Done = false;
   while (!Done) {
     bool UpdateLocLex = true;
 
     // The period in the dot operator (e.g., [ebx].foo.bar) is parsed as an
     // identifier.  Don't try an parse it as a register.
     if (Tok.getString().startswith("."))
       break;
case AsmToken::Identifier: {
         UpdateLocLex = false;
         break;
       } else {
         if (!isParsingInlineAsm()) {
           if (getParser().parsePrimaryExpr(Val, End))
             return Error(Tok.getLoc(), "Unexpected identifier!");
         } else {
           // This is a dot operator, not an adjacent identifier.
-          if (Identifier.find('.') != StringRef::npos) {
+          if (Identifier.find('.') != StringRef::npos &&
+              PrevTK == AsmToken::RBrac) {
             return false;
           } else {
             InlineAsmIdentifierInfo &Info = SM.getIdentifierInfo();
             if (ParseIntelIdentifier(Val, Identifier, Info,
                                      /*Unevaluated=*/false, End))
               return true;
           }
         }
while (!Done) {
     case AsmToken::LParen:  SM.onLParen(); break;
     case AsmToken::RParen:  SM.onRParen(); break;
     }
     if (SM.hadError())
       return Error(Tok.getLoc(), "unknown token in expression");
 
     if (!Done && UpdateLocLex)
       End = consumeToken();
+
+    PrevTK = TK;
   }
   return false;
 }
 
 std::unique_ptr<X86Operand>
 X86AsmParser::ParseIntelBracExpression(unsigned SegReg, SMLoc Start,
                                        int64_t ImmDisp, unsigned Size) {
   MCAsmParser &Parser = getParser();