diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -7196,7 +7196,7 @@
     // to obey basic rules for definitions dominating uses which this
     // analysis depends on.
     if (!DT.isReachableFromEntry(I->getParent()))
-      return getUnknown(UndefValue::get(V->getType()));
+      return getUnknown(PoisonValue::get(V->getType()));
   } else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
     return getConstant(CI);
   else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
diff --git a/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll b/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
--- a/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
+++ b/llvm/test/Analysis/ScalarEvolution/shift-recurrences.ll
@@ -389,9 +389,9 @@
 ; CHECK-LABEL: 'unreachable_phi'
 ; CHECK-NEXT:  Classifying expressions for: @unreachable_phi
 ; CHECK-NEXT:    %p_58.addr.1 = phi i32 [ undef, %unreachable1 ], [ %sub2629, %unreachable2 ]
-; CHECK-NEXT:    --> undef U: full-set S: full-set
+; CHECK-NEXT:    --> poison U: full-set S: full-set
 ; CHECK-NEXT:    %sub2629 = sub i32 %p_58.addr.1, 1
-; CHECK-NEXT:    --> undef U: full-set S: full-set
+; CHECK-NEXT:    --> poison U: full-set S: full-set
 ; CHECK-NEXT:  Determining loop execution counts for: @unreachable_phi
 ;
 entry:
@@ -415,7 +415,7 @@
 ; CHECK-NEXT:    %p_58.addr.1 = phi i32 [ undef, %header ], [ %sub2629, %unreachable ]
 ; CHECK-NEXT:    --> %p_58.addr.1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %header: Variant }
 ; CHECK-NEXT:    %sub2629 = sub i32 %p_58.addr.1, 1
-; CHECK-NEXT:    --> undef U: full-set S: full-set
+; CHECK-NEXT:    --> poison U: full-set S: full-set
 ; CHECK-NEXT:  Determining loop execution counts for: @unreachable_binop
 ; CHECK-NEXT:  Loop %header: Unpredictable backedge-taken count.
 ; CHECK-NEXT:  Loop %header: Unpredictable max backedge-taken count.
diff --git a/llvm/test/Analysis/ScalarEvolution/unreachable-code.ll b/llvm/test/Analysis/ScalarEvolution/unreachable-code.ll
--- a/llvm/test/Analysis/ScalarEvolution/unreachable-code.ll
+++ b/llvm/test/Analysis/ScalarEvolution/unreachable-code.ll
@@ -1,7 +1,7 @@
 ; RUN: opt < %s -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s
 
 ; CHECK: %t = add i64 %t, 1
-; CHECK: -->  undef
+; CHECK: -->  poison
 
 define void @foo() {
 entry: