[PATCH] D83887: Add hashing support for std::tuple

[Michael Forster via Phabricator via llvm-commits]

MForster updated this revision to Diff 278380.
MForster added a comment.

Fix diff.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83887/new/

https://reviews.llvm.org/D83887

Files:
  llvm/include/llvm/ADT/Hashing.h
  llvm/unittests/ADT/HashingTest.cpp


Index: llvm/unittests/ADT/HashingTest.cpp
===================================================================
--- llvm/unittests/ADT/HashingTest.cpp
+++ llvm/unittests/ADT/HashingTest.cpp
@@ -101,6 +101,17 @@
             hash_value(std::make_pair(obj1, std::make_pair(obj2, obj3))));
 }
 
+TEST(HashingTest, HashValueStdTuple) {
+  EXPECT_EQ(hash_combine(), hash_value(std::make_tuple()));
+  EXPECT_EQ(hash_combine(42), hash_value(std::make_tuple(42)));
+  EXPECT_EQ(hash_combine(42, 'c'), hash_value(std::make_tuple(42, 'c')));
+
+  EXPECT_NE(hash_combine(43, 42), hash_value(std::make_tuple(42, 43)));
+  EXPECT_NE(hash_combine(42, 43), hash_value(std::make_tuple(42ull, 43ull)));
+  EXPECT_NE(hash_combine(42, 43), hash_value(std::make_tuple(42, 43ull)));
+  EXPECT_NE(hash_combine(42, 43), hash_value(std::make_tuple(42ull, 43)));
+}
+
 TEST(HashingTest, HashValueStdString) {
   std::string s = "Hello World!";
   EXPECT_EQ(hash_combine_range(s.c_str(), s.c_str() + s.size()), hash_value(s));
Index: llvm/include/llvm/ADT/Hashing.h
===================================================================
--- llvm/include/llvm/ADT/Hashing.h
+++ llvm/include/llvm/ADT/Hashing.h
@@ -52,6 +52,7 @@
 #include <cassert>
 #include <cstring>
 #include <string>
+#include <tuple>
 #include <utility>
 
 namespace llvm {
@@ -112,11 +113,14 @@
 template <typename T, typename U>
 hash_code hash_value(const std::pair<T, U> &arg);
 
+/// Compute a hash_code for a tuple.
+template <typename... Ts>
+hash_code hash_value(const std::tuple<Ts...> &arg);
+
 /// Compute a hash_code for a standard string.
 template <typename T>
 hash_code hash_value(const std::basic_string<T> &arg);
 
-
 /// Override the execution seed with a fixed value.
 ///
 /// This hashing library uses a per-execution seed designed to change on each
@@ -645,6 +649,25 @@
   return hash_combine(arg.first, arg.second);
 }
 
+// Implementation details for the hash_value overload for std::tuple<...>(...).
+namespace hashing {
+namespace detail {
+
+template <typename... Ts, std::size_t... Indices>
+hash_code hash_value_tuple_helper(const std::tuple<Ts...> &arg,
+                                  std::index_sequence<Indices...> indices) {
+  return hash_combine(std::get<Indices>(arg)...);
+}
+
+} // namespace detail
+} // namespace hashing
+
+template <typename... Ts> hash_code hash_value(const std::tuple<Ts...> &arg) {
+  // TODO: Use std::apply when LLVM starts using C++17.
+  return ::llvm::hashing::detail::hash_value_tuple_helper(
+      arg, typename std::index_sequence_for<Ts...>());
+}
+
 // Declared and documented above, but defined here so that any of the hashing
 // infrastructure is available.
 template <typename T>


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