From 338a94e577a5ed4f84b1532e605f1c6525252cb8 Mon Sep 17 00:00:00 2001
From: Daniel James <daniel@calamity.org.uk>
Date: Mon, 1 May 2017 21:03:11 +0100
Subject: [PATCH] Better rvalue emulation support in extractors

Means that inserting rvalues into unordered_set/unordered_map won't
create a node if no insert is required.
---
 .../boost/unordered/detail/implementation.hpp | 21 +++++++
 test/unordered/unnecessary_copy_tests.cpp     | 61 +++++++++++++++----
 2 files changed, 71 insertions(+), 11 deletions(-)

diff --git a/include/boost/unordered/detail/implementation.hpp b/include/boost/unordered/detail/implementation.hpp
index c6aa43cf..879e0a15 100644
--- a/include/boost/unordered/detail/implementation.hpp
+++ b/include/boost/unordered/detail/implementation.hpp
@@ -4267,6 +4267,11 @@ template <class ValueType> struct set_extractor
 
     static key_type const& extract(value_type const& v) { return v; }
 
+    static key_type const& extract(BOOST_UNORDERED_RV_REF(value_type) v)
+    {
+        return v;
+    }
+
     static no_key extract() { return no_key(); }
 
     template <class Arg> static no_key extract(Arg const&) { return no_key(); }
@@ -4306,6 +4311,22 @@ template <class ValueType> struct map_extractor
         return v.first;
     }
 
+#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+    template <class Second>
+    static key_type const& extract(
+        boost::rv<std::pair<key_type, Second> > const& v)
+    {
+        return v.first;
+    }
+
+    template <class Second>
+    static key_type const& extract(
+        boost::rv<std::pair<key_type const, Second> > const& v)
+    {
+        return v.first;
+    }
+#endif
+
     template <class Arg1>
     static key_type const& extract(key_type const& k, Arg1 const&)
     {
diff --git a/test/unordered/unnecessary_copy_tests.cpp b/test/unordered/unnecessary_copy_tests.cpp
index 9618778b..3a5424bb 100644
--- a/test/unordered/unnecessary_copy_tests.cpp
+++ b/test/unordered/unnecessary_copy_tests.cpp
@@ -180,6 +180,53 @@ template <class T> void unnecessary_copy_insert_test(T*)
     reset();
     x.insert(a);
     COPY_COUNT(1);
+    MOVE_COUNT(0);
+}
+
+template <class T> void unnecessary_copy_insert_rvalue_set_test(T*)
+{
+    T x;
+    BOOST_DEDUCED_TYPENAME T::value_type a;
+    reset();
+    x.insert(boost::move(a));
+    COPY_COUNT(0);
+    MOVE_COUNT(1);
+
+    BOOST_DEDUCED_TYPENAME T::value_type a2;
+    reset();
+    x.insert(boost::move(a));
+    COPY_COUNT(0);
+    MOVE_COUNT((x.size() == 2 ? 1 : 0));
+}
+
+template <class T> void unnecessary_copy_insert_rvalue_map_test(T*)
+{
+    // Doesn't currently try to emulate std::pair move construction,
+    // so std::pair's require a copy. Could try emulating it in
+    // construct_from_args.
+
+    T x;
+    BOOST_DEDUCED_TYPENAME T::value_type a;
+    reset();
+    x.insert(boost::move(a));
+#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+    COPY_COUNT(1);
+    MOVE_COUNT(0);
+#else
+    COPY_COUNT(0);
+    MOVE_COUNT(1);
+#endif
+
+    BOOST_DEDUCED_TYPENAME T::value_type a2;
+    reset();
+    x.insert(boost::move(a));
+#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+    COPY_COUNT((x.size() == 2 ? 1 : 0));
+    MOVE_COUNT(0);
+#else
+    COPY_COUNT(0);
+    MOVE_COUNT((x.size() == 2 ? 1 : 0));
+#endif
 }
 
 boost::unordered_set<count_copies>* set;
@@ -188,6 +235,8 @@ boost::unordered_map<int, count_copies>* map;
 boost::unordered_multimap<int, count_copies>* multimap;
 
 UNORDERED_TEST(unnecessary_copy_insert_test, ((set)(multiset)(map)(multimap)))
+UNORDERED_TEST(unnecessary_copy_insert_rvalue_set_test, ((set)(multiset)))
+UNORDERED_TEST(unnecessary_copy_insert_rvalue_map_test, ((map)(multimap)))
 
 template <class T> void unnecessary_copy_emplace_test(T*)
 {
@@ -315,15 +364,10 @@ UNORDERED_AUTO_TEST(unnecessary_copy_emplace_set_test)
     // the existing element.
     reset();
     x.emplace();
-#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) ||                             \
-    !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+
     // source_cost doesn't make much sense here, but it seems to fit.
     COPY_COUNT(1);
     MOVE_COUNT(source_cost);
-#else
-    COPY_COUNT(1);
-    MOVE_COUNT(1 + source_cost);
-#endif
 #endif
 
     //
@@ -347,13 +391,8 @@ UNORDERED_AUTO_TEST(unnecessary_copy_emplace_set_test)
     // No move should take place.
     reset();
     x.emplace(boost::move(a));
-#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
     COPY_COUNT(0);
     MOVE_COUNT(0);
-#else
-    COPY_COUNT(0);
-    MOVE_COUNT(1);
-#endif
 
     // Use a new value for cases where a did get moved...
     count_copies b;