diff --git a/clang/include/clang/AST/ExprCXX.h b/clang/include/clang/AST/ExprCXX.h
index 37d310ef967d9c..24278016431837 100644
--- a/clang/include/clang/AST/ExprCXX.h
+++ b/clang/include/clang/AST/ExprCXX.h
@@ -2397,6 +2397,7 @@ class CXXNewExpr final
     case CXXNewInitializationStyle::List:
       return true;
     }
+    llvm_unreachable("Unknown initializer");
   }
 
   /// The kind of initializer this new-expression has.
diff --git a/clang/lib/Analysis/FlowSensitive/SimplifyConstraints.cpp b/clang/lib/Analysis/FlowSensitive/SimplifyConstraints.cpp
index decb928f218a81..00a3104a57b6ba 100644
--- a/clang/lib/Analysis/FlowSensitive/SimplifyConstraints.cpp
+++ b/clang/lib/Analysis/FlowSensitive/SimplifyConstraints.cpp
@@ -42,6 +42,7 @@ substitute(const Formula &F,
     return arena.makeEquals(substitute(*F.operands()[0], Substitutions, arena),
                             substitute(*F.operands()[1], Substitutions, arena));
   }
+  llvm_unreachable("Unknown formula kind");
 }
 
 // Returns the result of replacing atoms in `Atoms` with the leader of their
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index c07462aa244440..67bc847ff2a60e 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -2050,6 +2050,7 @@ ExprResult Sema::BuildCXXNew(SourceRange Range, bool UseGlobal,
                                                   Initializer->getBeginLoc(),
                                                   Initializer->getEndLoc());
     }
+    llvm_unreachable("Unknown initialization kind");
   }();
 
   // C++11 [dcl.spec.auto]p6. Deduce the type which 'auto' stands in for.