diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.h b/llvm/utils/TableGen/CodeGenDAGPatterns.h
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.h
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.h
@@ -298,8 +298,11 @@
   /// unchanged.
   bool EnforceAny(TypeSetByHwMode &Out);
   /// Make sure that for each type in \p Small, there exists a larger type
-  /// in \p Big.
-  bool EnforceSmallerThan(TypeSetByHwMode &Small, TypeSetByHwMode &Big);
+  /// in \p Big. \p SmallIsVT indicates that this is being called for
+  /// SDTCisVTSmallerThanOp. In that case the TypeSetByHwMode is re-created for
+  /// each call and needs special consideration in how we detect changes.
+  bool EnforceSmallerThan(TypeSetByHwMode &Small, TypeSetByHwMode &Big,
+                          bool SmallIsVT = false);
   /// 1. Ensure that for each type T in \p Vec, T is a vector type, and that
   ///    for each type U in \p Elem, U is a scalar type.
   /// 2. Ensure that for each (scalar) type U in \p Elem, there exists a
diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -451,13 +451,16 @@
 }
 
 /// Make sure that for each type in Small, there exists a larger type in Big.
-bool TypeInfer::EnforceSmallerThan(TypeSetByHwMode &Small,
-                                   TypeSetByHwMode &Big) {
+bool TypeInfer::EnforceSmallerThan(TypeSetByHwMode &Small, TypeSetByHwMode &Big,
+                                   bool SmallIsVT) {
   ValidateOnExit _1(Small, *this), _2(Big, *this);
   if (TP.hasError())
     return false;
   bool Changed = false;
 
+  assert((!SmallIsVT || !Small.empty()) &&
+         "Small should not be empty for SDTCisVTSmallerThanOp");
+
   if (Small.empty())
     Changed |= EnforceAny(Small);
   if (Big.empty())
@@ -476,7 +479,9 @@
     TypeSetByHwMode::SetType &S = Small.get(M);
     TypeSetByHwMode::SetType &B = Big.get(M);
 
-    if (any_of(S, isIntegerOrPtr) && any_of(S, isIntegerOrPtr)) {
+    assert((!SmallIsVT || !S.empty()) && "Expected non-empty type");
+
+    if (any_of(S, isIntegerOrPtr) && any_of(B, isIntegerOrPtr)) {
       auto NotInt = [](MVT VT) { return !isIntegerOrPtr(VT); };
       Changed |= berase_if(S, NotInt);
       Changed |= berase_if(B, NotInt);
@@ -484,6 +489,11 @@
       auto NotFP = [](MVT VT) { return !isFloatingPoint(VT); };
       Changed |= berase_if(S, NotFP);
       Changed |= berase_if(B, NotFP);
+    } else if (SmallIsVT && B.empty()) {
+      // B is empty and since S is a specific VT, it will never be empty. Don't
+      // report this as a change, just clear S and continue. This prevents an
+      // infinite loop.
+      S.clear();
     } else if (S.empty() || B.empty()) {
       Changed = !S.empty() || !B.empty();
       S.clear();
@@ -1637,7 +1647,8 @@
       getOperandNum(x.SDTCisVTSmallerThanOp_Info.OtherOperandNum, N, NodeInfo,
                     OResNo);
 
-    return TI.EnforceSmallerThan(TypeListTmp, OtherNode->getExtType(OResNo));
+    return TI.EnforceSmallerThan(TypeListTmp, OtherNode->getExtType(OResNo),
+                                 /*SmallIsVT*/ true);
   }
   case SDTCisOpSmallerThanOp: {
     unsigned BResNo = 0;