2 files changed, 15 insertions, 16 deletions

diff --git a/llvm/lib/TableGen/Record.cpp b/llvm/lib/TableGen/Record.cpp
index c94bd59c8ad..80c0973644b 100644
--- a/llvm/lib/TableGen/Record.cpp
+++ b/llvm/lib/TableGen/Record.cpp
@@ -141,6 +141,10 @@ bool RecordRecTy::typeIsConvertibleTo(const RecTy *RHS) const {
   if (RTy->getRecord() == Rec || Rec->isSubClassOf(RTy->getRecord()))
     return true;
 
+  for (const auto &SCPair : RTy->getRecord()->getSuperClasses())
+    if (Rec->isSubClassOf(SCPair.first))
+      return true;
+
   return false;
 }
 
@@ -169,16 +173,6 @@ RecTy *llvm::resolveTypes(RecTy *T1, RecTy *T2) {
         return NewType2;
     }
   }
-
-  if (ListRecTy *ListTy1 = dyn_cast<ListRecTy>(T1)) {
-    if (ListRecTy *ListTy2 = dyn_cast<ListRecTy>(T2)) {
-      RecTy* NewType = resolveTypes(ListTy1->getElementType(),
-                                    ListTy2->getElementType());
-      if (NewType)
-        return NewType->getListTy();
-    }
-  }
-
   return nullptr;
 }
 
diff --git a/llvm/lib/TableGen/TGParser.cpp b/llvm/lib/TableGen/TGParser.cpp
index 4dd05fd3297..10345b99706 100644
--- a/llvm/lib/TableGen/TGParser.cpp
+++ b/llvm/lib/TableGen/TGParser.cpp
@@ -198,8 +198,6 @@ bool TGParser::AddSubClass(Record *CurRec, SubClassReference &SubClass) {
 
   // Since everything went well, we can now set the "superclass" list for the
   // current record.
-  CurRec->addSuperClass(SC, SubClass.RefRange);
-
   ArrayRef<std::pair<Record *, SMRange>> SCs = SC->getSuperClasses();
   for (const auto &SCPair : SCs) {
     if (CurRec->isSubClassOf(SCPair.first))
@@ -207,6 +205,11 @@ bool TGParser::AddSubClass(Record *CurRec, SubClassReference &SubClass) {
                    "Already subclass of '" + SCPair.first->getName() + "'!\n");
     CurRec->addSuperClass(SCPair.first, SCPair.second);
   }
+
+  if (CurRec->isSubClassOf(SC))
+    return Error(SubClass.RefRange.Start,
+                 "Already subclass of '" + SC->getName() + "'!\n");
+  CurRec->addSuperClass(SC, SubClass.RefRange);
   return false;
 }
 
@@ -1064,10 +1067,12 @@ Init *TGParser::ParseOperation(Record *CurRec, RecTy *ItemType) {
         return nullptr;
       }
 
-      Type = resolveTypes(MHSTy, RHSTy);
-      if (!Type) {
-        TokError(Twine("inconsistent types '") + MHSTy->getAsString() +
-                 "' and '" + RHSTy->getAsString() + "' for !if");
+      if (MHSTy->typeIsConvertibleTo(RHSTy)) {
+        Type = RHSTy;
+      } else if (RHSTy->typeIsConvertibleTo(MHSTy)) {
+        Type = MHSTy;
+      } else {
+        TokError("inconsistent types for !if");
         return nullptr;
       }
       break;