[ms-inline asm] Make comment more verbose and add an assert.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163125 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/AsmMatcherEmitter.cpp b/utils/TableGen/AsmMatcherEmitter.cpp
index a4744ba..3c107a2 100644
--- a/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/utils/TableGen/AsmMatcherEmitter.cpp
@@ -1721,7 +1721,8 @@
        << "      ++MCOperandNum;\n"
        << "      break;\n"
        << "    case CVT_Tied:\n"
-       << "      //Inst.getOperand(*(p + 1)));\n"
+       << "      // FIXME: Tied operand calculation not supported.\n"
+       << "      assert (0 && \"GetMCInstOperandNumImpl() doesn't support tied operands, yet!\");\n"
        << "      break;\n";
 
   // Pre-populate the operand conversion kinds with the standard always