Index: llvm/lib/Transforms/IPO/AttributorAttributes.cpp
===================================================================
--- llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -7786,8 +7786,18 @@
 
 struct AANoUndefReturned final
     : AAReturnedFromReturnedValues<AANoUndef, AANoUndefImpl> {
-  AANoUndefReturned(const IRPosition &IRP, Attributor &A)
-      : AAReturnedFromReturnedValues<AANoUndef, AANoUndefImpl>(IRP, A) {}
+  using Base = AAReturnedFromReturnedValues<AANoUndef, AANoUndefImpl>;
+  AANoUndefReturned(const IRPosition &IRP, Attributor &A) : Base(IRP, A) {}
+
+  /// See AbstractAttribute::updateImpl(...).
+  ChangeStatus updateImpl(Attributor &A) override {
+    auto &LivenessAA = A.getAAFor<AAIsDead>(*this, getIRPosition());
+    // When the returned position is dead, returned values will be replaced with
+    // undef values by AAIsDead. So we don't deduce noundef for this position.
+    if (LivenessAA.isKnown())
+      return indicatePessimisticFixpoint();
+    return Base::updateImpl(A);
+  }
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override { STATS_DECLTRACK_FNRET_ATTR(noundef) }
Index: llvm/test/Transforms/Attributor/noundef.ll
===================================================================
--- llvm/test/Transforms/Attributor/noundef.ll
+++ llvm/test/Transforms/Attributor/noundef.ll
@@ -20,3 +20,21 @@
   call void @bar(i32* %x)
   ret void
 }
+
+define internal i8* @returned_dead() {
+; CHECK-LABEL: define internal noalias align 536870912 i8* @returned_dead(
+; CHECK-NEXT:    call void @unknown()
+; CHECK-NEXT:    ret i8* undef
+;
+  call void @unknown()
+  ret i8* null
+}
+
+define void @caller() {
+; CHECK-LABEL: @caller(
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8* @returned_dead()
+; CHECK-NEXT:    ret void
+;
+  call i8* @returned_dead()
+  ret void
+}