diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c7aeb0633e4ba..93d866384b482 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1801,8 +1801,11 @@ void DAGCombiner::Run(CombineLevel AtLevel) {
 
     if (N->getNumValues() == RV->getNumValues())
       DAG.ReplaceAllUsesWith(N, RV.getNode());
-    else
+    else {
+      assert(N->getValueType(0) == RV.getValueType() &&
+             N->getNumValues() == 1 && "Type mismatch");
       DAG.ReplaceAllUsesWith(N, &RV);
+    }
 
     // Push the new node and any users onto the worklist.  Omit this if the
     // new node is the EntryToken (e.g. if a store managed to get optimized
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 7d90296a3eea6..0e514ca1246b0 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -49253,8 +49253,10 @@ static SDValue combineX86SubCmpForFlags(SDNode *N, SDValue Flag,
     return SDValue();
 
   SDValue X = SetCC.getOperand(1);
-  // Replace API is called manually here b/c the number of results may change.
-  DAG.ReplaceAllUsesOfValueWith(Flag, X);
+  // sub has two results while X only have one. DAG combine assumes the value
+  // type matches.
+  if (N->getOpcode() == X86ISD::SUB)
+    X = DAG.getMergeValues({N->getOperand(0), X}, SDLoc(N));
 
   SDValue CCN = SetCC.getOperand(0);
   X86::CondCode CC =