diff --git a/llvm/include/llvm/Support/Casting.h b/llvm/include/llvm/Support/Casting.h
index b6bbff8..1b68640 100644
--- a/llvm/include/llvm/Support/Casting.h
+++ b/llvm/include/llvm/Support/Casting.h
@@ -605,6 +605,9 @@ LLVM_NODISCARD inline decltype(auto) dyn_cast(From &Val) {
 
 template <typename To, typename From>
 LLVM_NODISCARD inline decltype(auto) dyn_cast(From *Val) {
+#if defined(__clang__) && defined(NDEBUG)
+  __builtin_assume(Val);
+#endif
   return CastInfo<To, From *>::doCastIfPossible(Val);
 }