diff --git a/utils/TableGen/CodeGenDAGPatterns.cpp b/utils/TableGen/CodeGenDAGPatterns.cpp
index 003f108fa4c..e5d70cd084e 100644
--- a/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -872,6 +872,10 @@ bool TreePatternNode::ApplyTypeConstraints(TreePattern &TP, bool NotRegisters) {
         std::vector<unsigned char> VT;
         VT.push_back(MVT::iPTR);
         MadeChange = UpdateNodeType(VT, TP);
+      } else if (ResultNode->getName() == "unknown") {
+        std::vector<unsigned char> VT;
+        VT.push_back(MVT::isUnknown);
+        MadeChange = UpdateNodeType(VT, TP);
       } else {
         assert(ResultNode->isSubClassOf("RegisterClass") &&
                "Operands should be register classes!");
@@ -910,13 +914,15 @@ bool TreePatternNode::ApplyTypeConstraints(TreePattern &TP, bool NotRegisters) {
         MadeChange |= Child->UpdateNodeType(VT, TP);
       } else if (OperandNode->getName() == "ptr_rc") {
         MadeChange |= Child->UpdateNodeType(MVT::iPTR, TP);
+      } else if (OperandNode->getName() == "unknown") {
+        MadeChange |= Child->UpdateNodeType(MVT::isUnknown, TP);
       } else {
         assert(0 && "Unknown operand type!");
         abort();
       }
       MadeChange |= Child->ApplyTypeConstraints(TP, NotRegisters);
     }
-    
+
     if (ChildNo != getNumChildren())
       TP.error("Instruction '" + getOperator()->getName() +
                "' was provided too many operands!");
diff --git a/utils/TableGen/CodeGenInstruction.cpp b/utils/TableGen/CodeGenInstruction.cpp
index 0ee6b41d908..8b706479077 100644
--- a/utils/TableGen/CodeGenInstruction.cpp
+++ b/utils/TableGen/CodeGenInstruction.cpp
@@ -163,7 +163,7 @@ CodeGenInstruction::CodeGenInstruction(Record *R, const std::string &AsmStr)
       isVariadic = true;
       continue;
     } else if (!Rec->isSubClassOf("RegisterClass") && 
-               Rec->getName() != "ptr_rc")
+               Rec->getName() != "ptr_rc" && Rec->getName() != "unknown")
       throw "Unknown operand class '" + Rec->getName() +
             "' in instruction '" + R->getName() + "' instruction!";