diff --git a/llvm/include/llvm/Transforms/InstCombine/InstCombineWorklist.h b/llvm/include/llvm/Transforms/InstCombine/InstCombineWorklist.h
--- a/llvm/include/llvm/Transforms/InstCombine/InstCombineWorklist.h
+++ b/llvm/include/llvm/Transforms/InstCombine/InstCombineWorklist.h
@@ -24,8 +24,8 @@
 /// InstCombineWorklist - This is the worklist management logic for
 /// InstCombine.
 class InstCombineWorklist {
-  SmallVector<Instruction*, 256> Worklist;
-  DenseMap<Instruction*, unsigned> WorklistMap;
+  SmallVector<Instruction *, 256> Worklist;
+  DenseMap<Instruction *, unsigned> WorklistMap;
 
 public:
   InstCombineWorklist() = default;
@@ -38,6 +38,9 @@
   /// Add - Add the specified instruction to the worklist if it isn't already
   /// in it.
   void Add(Instruction *I) {
+    assert(I);
+    assert(I->getParent() && "Instruction not inserted yet?");
+
     if (WorklistMap.insert(std::make_pair(I, Worklist.size())).second) {
       LLVM_DEBUG(dbgs() << "IC: ADD: " << *I << '\n');
       Worklist.push_back(I);
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1189,7 +1189,9 @@
       // zext (or icmp, icmp) -> or (zext icmp), (zext icmp)
       Value *LCast = Builder.CreateZExt(LHS, CI.getType(), LHS->getName());
       Value *RCast = Builder.CreateZExt(RHS, CI.getType(), RHS->getName());
-      BinaryOperator *Or = BinaryOperator::Create(Instruction::Or, LCast, RCast);
+      Value *Or = Builder.CreateOr(LCast, RCast, CI.getName());
+      if (auto *OrInst = dyn_cast<Instruction>(Or))
+        Builder.SetInsertPoint(OrInst);
 
       // Perform the elimination.
       if (auto *LZExt = dyn_cast<ZExtInst>(LCast))
@@ -1197,7 +1199,7 @@
       if (auto *RZExt = dyn_cast<ZExtInst>(RCast))
         transformZExtICmp(RHS, *RZExt);
 
-      return Or;
+      return replaceInstUsesWith(CI, Or);
     }
   }
 
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3361,10 +3361,6 @@
         // Move the name to the new instruction first.
         Result->takeName(I);
 
-        // Push the new instruction and any users onto the worklist.
-        Worklist.AddUsersToWorkList(*Result);
-        Worklist.Add(Result);
-
         // Insert the new instruction into the basic block...
         BasicBlock *InstParent = I->getParent();
         BasicBlock::iterator InsertPos = I->getIterator();
@@ -3376,6 +3372,10 @@
 
         InstParent->getInstList().insert(InsertPos, Result);
 
+        // Push the new instruction and any users onto the worklist.
+        Worklist.AddUsersToWorkList(*Result);
+        Worklist.Add(Result);
+
         eraseInstFromFunction(*I);
       } else {
         LLVM_DEBUG(dbgs() << "IC: Mod = " << OrigI << '\n'
diff --git a/llvm/test/Transforms/InstCombine/zext-or-icmp.ll b/llvm/test/Transforms/InstCombine/zext-or-icmp.ll
--- a/llvm/test/Transforms/InstCombine/zext-or-icmp.ll
+++ b/llvm/test/Transforms/InstCombine/zext-or-icmp.ll
@@ -15,7 +15,7 @@
 ; CHECK-NEXT:    %toBool2 = icmp eq i8 %b, 0
 ; CHECK-NEXT:    %toBool22 = zext i1 %toBool2 to i8
 ; CHECK-NEXT:    %1 = xor i8 %mask, 1
-; CHECK-NEXT:    %zext = or i8 %1, %toBool22
+; CHECK-NEXT:    %zext3 = or i8 %1, %toBool22
 ; CHECK-NEXT:    ret i8 %zext
 }