diff --git a/llvm/include/llvm/ADT/BitVector.h b/llvm/include/llvm/ADT/BitVector.h
--- a/llvm/include/llvm/ADT/BitVector.h
+++ b/llvm/include/llvm/ADT/BitVector.h
@@ -542,7 +542,7 @@
   }
 
   template <class F, class... ArgTys>
-  static BitVector &apply(F &&f, BitVector &Out, BitVector const &Arg,
+  static BitVector &apply(const F &f, BitVector &Out, BitVector const &Arg,
                           ArgTys const &...Args) {
     assert(llvm::all_of(
                std::initializer_list<unsigned>{Args.size()...},
diff --git a/llvm/include/llvm/Support/Error.h b/llvm/include/llvm/Support/Error.h
--- a/llvm/include/llvm/Support/Error.h
+++ b/llvm/include/llvm/Support/Error.h
@@ -835,7 +835,7 @@
   template <typename HandlerT>
   static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) {
     assert(appliesTo(*E) && "Applying incorrect handler");
-    return H(static_cast<ErrT &>(*E));
+    return std::forward<HandlerT>(H)(static_cast<ErrT &>(*E));
   }
 };
 
@@ -849,7 +849,7 @@
   template <typename HandlerT>
   static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) {
     assert(appliesTo(*E) && "Applying incorrect handler");
-    H(static_cast<ErrT &>(*E));
+    std::forward<HandlerT>(H)(static_cast<ErrT &>(*E));
     return Error::success();
   }
 };
@@ -866,7 +866,7 @@
   static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) {
     assert(appliesTo(*E) && "Applying incorrect handler");
     std::unique_ptr<ErrT> SubE(static_cast<ErrT *>(E.release()));
-    return H(std::move(SubE));
+    return std::forward<HandlerT>(H)(std::move(SubE));
   }
 };
 
@@ -882,7 +882,7 @@
   static Error apply(HandlerT &&H, std::unique_ptr<ErrorInfoBase> E) {
     assert(appliesTo(*E) && "Applying incorrect handler");
     std::unique_ptr<ErrT> SubE(static_cast<ErrT *>(E.release()));
-    H(std::move(SubE));
+    std::forward<HandlerT>(H)(std::move(SubE));
     return Error::success();
   }
 };
diff --git a/llvm/include/llvm/Support/HashBuilder.h b/llvm/include/llvm/Support/HashBuilder.h
--- a/llvm/include/llvm/Support/HashBuilder.h
+++ b/llvm/include/llvm/Support/HashBuilder.h
@@ -100,7 +100,7 @@
       : HashBuilderBase<HasherT>(Hasher) {}
   template <typename... ArgTypes>
   explicit HashBuilderImpl(ArgTypes &&...Args)
-      : HashBuilderBase<HasherT>(Args...) {}
+      : HashBuilderBase<HasherT>(std::forward<ArgTypes>(Args)...) {}
 
   /// Implement hashing for hashable data types, e.g. integral or enum values.
   template <typename T>