From f018bd9ae7cf418188285c03d8fe2aacecbd4730 Mon Sep 17 00:00:00 2001
From: Doug Gregor <dgregor@apple.com>
Date: Tue, 27 Sep 2016 12:33:08 -0700
Subject: [PATCH] Add hash_value support for tuples.

---
 include/llvm/ADT/Hashing.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/include/llvm/ADT/Hashing.h b/include/llvm/ADT/Hashing.h
index c3b574102f6..8b1a305852b 100644
--- a/include/llvm/ADT/Hashing.h
+++ b/include/llvm/ADT/Hashing.h
@@ -53,6 +53,7 @@
 #include <cassert>
 #include <cstring>
 #include <string>
+#include <tuple>
 #include <utility>
 
 namespace llvm {
@@ -656,6 +657,33 @@ hash_code hash_value(const std::basic_string<T> &arg) {
   return hash_combine_range(arg.begin(), arg.end());
 }
 
+template<unsigned ...Indices>
+struct UnsignedConstantIndexSet { };
+
+template<unsigned I, unsigned N, unsigned ...Indices>
+struct MakeUnsignedConstantIndexSet {
+  typedef typename MakeUnsignedConstantIndexSet<I+1, N, Indices..., I>::Type
+    Type;
+};
+
+template<unsigned N, unsigned ...Indices>
+struct MakeUnsignedConstantIndexSet<N, N, Indices...> {
+  typedef UnsignedConstantIndexSet<Indices...> Type;
+};
+
+template <typename ...Ts, unsigned ...Indices>
+hash_code hash_value_tuple_helper(const std::tuple<Ts...> &arg,
+                                  UnsignedConstantIndexSet<Indices...> indices) {
+  return hash_combine(hash_value(std::get<Indices>(arg))...);
+}
+
+template <typename ...Ts>
+hash_code hash_value(const std::tuple<Ts...> &arg) {
+  return hash_value_tuple_helper(
+           arg, 
+           typename MakeUnsignedConstantIndexSet<0, sizeof...(Ts)>::Type());
+}
+
 } // namespace llvm
 
 #endif