From 160ba647becf04fbebb33df47a826f6dd55abb6e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Pedro=20Bol=C3=ADvar=20Puente?= <raskolnikov@gnu.org>
Date: Thu, 2 Jun 2022 11:45:52 +0200
Subject: [PATCH] Improve sequential initialization of HAMTs

With this implementation, it uses transients also when using a tracing
garbage collector -- before it would be optimized only when using
reference counting.
---
 immer/detail/hamts/champ.hpp | 22 ++++++++++++++++++++++
 immer/map.hpp                | 12 ++++--------
 immer/set.hpp                | 12 ++++--------
 immer/table.hpp              | 18 +++++++-----------
 4 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/immer/detail/hamts/champ.hpp b/immer/detail/hamts/champ.hpp
index 292527f4..5f635097 100644
--- a/immer/detail/hamts/champ.hpp
+++ b/immer/detail/hamts/champ.hpp
@@ -89,6 +89,28 @@ struct champ
             node_t::delete_deep(root, 0);
     }
 
+    template <typename U>
+    static auto from_initializer_list(std::initializer_list<U> values)
+    {
+        auto e      = owner_t{};
+        auto result = champ{empty()};
+        for (auto&& v : values)
+            result.add_mut(e, v);
+        return result;
+    }
+
+    template <typename Iter,
+              typename Sent,
+              std::enable_if_t<compatible_sentinel_v<Iter, Sent>, bool> = true>
+    static auto from_range(Iter first, Sent last)
+    {
+        auto e      = owner_t{};
+        auto result = champ{empty()};
+        for (; first != last; ++first)
+            result.add_mut(e, *first);
+        return result;
+    }
+
     template <typename Fn>
     void for_each_chunk(Fn&& fn) const
     {
diff --git a/immer/map.hpp b/immer/map.hpp
index 33315ad9..acbbc0b1 100644
--- a/immer/map.hpp
+++ b/immer/map.hpp
@@ -170,10 +170,8 @@ class map
      * Constructs a map containing the elements in `values`.
      */
     map(std::initializer_list<value_type> values)
-    {
-        for (auto&& v : values)
-            *this = std::move(*this).insert(v);
-    }
+        : impl_{impl_t::from_initializer_list(values)}
+    {}
 
     /*!
      * Constructs a map containing the elements in the range
@@ -184,10 +182,8 @@ class map
               std::enable_if_t<detail::compatible_sentinel_v<Iter, Sent>,
                                bool> = true>
     map(Iter first, Sent last)
-    {
-        for (; first != last; ++first)
-            *this = std::move(*this).insert(*first);
-    }
+        : impl_{impl_t::from_range(first, last)}
+    {}
 
     /*!
      * Default constructor.  It creates a map of `size() == 0`.  It
diff --git a/immer/set.hpp b/immer/set.hpp
index 247ef83f..a8199b22 100644
--- a/immer/set.hpp
+++ b/immer/set.hpp
@@ -95,10 +95,8 @@ class set
      * Constructs a set containing the elements in `values`.
      */
     set(std::initializer_list<value_type> values)
-    {
-        for (auto&& v : values)
-            *this = std::move(*this).insert(v);
-    }
+        : impl_{impl_t::from_initializer_list(values)}
+    {}
 
     /*!
      * Constructs a set containing the elements in the range
@@ -109,10 +107,8 @@ class set
               std::enable_if_t<detail::compatible_sentinel_v<Iter, Sent>,
                                bool> = true>
     set(Iter first, Sent last)
-    {
-        for (; first != last; ++first)
-            *this = std::move(*this).insert(*first);
-    }
+        : impl_{impl_t::from_range(first, last)}
+    {}
 
     /*!
      * Returns an iterator pointing at the first element of the
diff --git a/immer/table.hpp b/immer/table.hpp
index dd45012c..c4118054 100644
--- a/immer/table.hpp
+++ b/immer/table.hpp
@@ -186,10 +186,8 @@ class table
      * Constructs a table containing the elements in `values`.
      */
     table(std::initializer_list<value_type> values)
-    {
-        for (auto&& v : values)
-            *this = std::move(*this).insert(v);
-    }
+        : impl_{impl_t::from_initializer_list(values)}
+    {}
 
     /*!
      * Constructs a table containing the elements in the range
@@ -200,10 +198,8 @@ class table
               std::enable_if_t<detail::compatible_sentinel_v<Iter, Sent>,
                                bool> = true>
     table(Iter first, Sent last)
-    {
-        for (; first != last; ++first)
-            *this = std::move(*this).insert(*first);
-    }
+        : impl_{impl_t::from_range(first, last)}
+    {}
 
     /*!
      * Default constructor.  It creates a table of `size() == 0`. It
@@ -467,7 +463,7 @@ class table
     table&& update_move(std::true_type, key_type k, Fn&& fn)
     {
         impl_.template update_mut<project_value, default_value, combine_value>(
-            std::move(k), std::forward<Fn>(fn));
+            {}, std::move(k), std::forward<Fn>(fn));
         return std::move(*this);
     }
 
@@ -475,8 +471,8 @@ class table
     table update_move(std::false_type, key_type k, Fn&& fn)
     {
         return impl_
-            .template update_mut<project_value, default_value, combine_value>(
-                {}, std::move(k), std::forward<Fn>(fn));
+            .template update<project_value, default_value, combine_value>(
+                std::move(k), std::forward<Fn>(fn));
     }
 
     table&& erase_move(std::true_type, const key_type& value)