From a2dcc642c1737721bafe54605c7826fa08d18f47 Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Thu, 21 May 2020 01:06:40 -0300
Subject: [PATCH] map_interval: Add interval allocator and drop hack

Drop the std::list hack to allocate memory indefinitely.

Instead use a custom allocator that keeps references valid until
destruction. This allocates fixed chunks of memory and puts pointers in
a free list. When an allocation is no longer used put it back to the
free list, this doesn't heap allocate because std::vector doesn't change
the capacity. If the free list is empty, allocate a new chunk.
---
 src/video_core/CMakeLists.txt                |  1 +
 src/video_core/buffer_cache/buffer_cache.h   |  7 ++--
 src/video_core/buffer_cache/map_interval.cpp | 33 ++++++++++++++++
 src/video_core/buffer_cache/map_interval.h   | 41 ++++++++++++++++++++
 4 files changed, 79 insertions(+), 3 deletions(-)
 create mode 100644 src/video_core/buffer_cache/map_interval.cpp

diff --git a/src/video_core/CMakeLists.txt b/src/video_core/CMakeLists.txt
index d23c538437..f00c71daee 100644
--- a/src/video_core/CMakeLists.txt
+++ b/src/video_core/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_library(video_core STATIC
     buffer_cache/buffer_block.h
     buffer_cache/buffer_cache.h
+    buffer_cache/map_interval.cpp
     buffer_cache/map_interval.h
     dirty_flags.cpp
     dirty_flags.h
diff --git a/src/video_core/buffer_cache/buffer_cache.h b/src/video_core/buffer_cache/buffer_cache.h
index 0c8500c044..2262259c7f 100644
--- a/src/video_core/buffer_cache/buffer_cache.h
+++ b/src/video_core/buffer_cache/buffer_cache.h
@@ -284,8 +284,8 @@ protected:
             MarkRegionAsWritten(new_map.start, new_map.end - 1);
             new_map.is_written = true;
         }
-        // Temporary hack, leaks memory and it's not cache local
-        MapInterval* const storage = &mapped_addresses_storage.emplace_back(new_map);
+        MapInterval* const storage = mapped_addresses_allocator.Allocate();
+        *storage = new_map;
         mapped_addresses.insert(*storage);
         return storage;
     }
@@ -313,6 +313,7 @@ protected:
         const auto it = mapped_addresses.find(*map);
         ASSERT(it != mapped_addresses.end());
         mapped_addresses.erase(it);
+        mapped_addresses_allocator.Release(map);
     }
 
 private:
@@ -577,7 +578,7 @@ private:
     u64 buffer_offset = 0;
     u64 buffer_offset_base = 0;
 
-    std::list<MapInterval> mapped_addresses_storage; // Temporary hack
+    MapIntervalAllocator mapped_addresses_allocator;
     boost::intrusive::set<MapInterval, boost::intrusive::compare<MapIntervalCompare>>
         mapped_addresses;
 
diff --git a/src/video_core/buffer_cache/map_interval.cpp b/src/video_core/buffer_cache/map_interval.cpp
new file mode 100644
index 0000000000..62587e18a1
--- /dev/null
+++ b/src/video_core/buffer_cache/map_interval.cpp
@@ -0,0 +1,33 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <algorithm>
+#include <array>
+#include <cstddef>
+#include <memory>
+
+#include "video_core/buffer_cache/map_interval.h"
+
+namespace VideoCommon {
+
+MapIntervalAllocator::MapIntervalAllocator() {
+    FillFreeList(first_chunk);
+}
+
+MapIntervalAllocator::~MapIntervalAllocator() = default;
+
+void MapIntervalAllocator::AllocateNewChunk() {
+    *new_chunk = std::make_unique<Chunk>();
+    FillFreeList(**new_chunk);
+    new_chunk = &(*new_chunk)->next;
+}
+
+void MapIntervalAllocator::FillFreeList(Chunk& chunk) {
+    const std::size_t old_size = free_list.size();
+    free_list.resize(old_size + chunk.data.size());
+    std::transform(chunk.data.rbegin(), chunk.data.rend(), free_list.begin() + old_size,
+                   [](MapInterval& interval) { return &interval; });
+}
+
+} // namespace VideoCommon
diff --git a/src/video_core/buffer_cache/map_interval.h b/src/video_core/buffer_cache/map_interval.h
index 45705cccf9..fe0bcd1d8f 100644
--- a/src/video_core/buffer_cache/map_interval.h
+++ b/src/video_core/buffer_cache/map_interval.h
@@ -4,6 +4,11 @@
 
 #pragma once
 
+#include <array>
+#include <cstddef>
+#include <memory>
+#include <vector>
+
 #include <boost/intrusive/set_hook.hpp>
 
 #include "common/common_types.h"
@@ -12,6 +17,8 @@
 namespace VideoCommon {
 
 struct MapInterval : public boost::intrusive::set_base_hook<boost::intrusive::optimize_size<true>> {
+    MapInterval() = default;
+
     /*implicit*/ MapInterval(VAddr start_) noexcept : start{start_} {}
 
     explicit MapInterval(VAddr start_, VAddr end_, GPUVAddr gpu_addr_) noexcept
@@ -48,4 +55,38 @@ struct MapIntervalCompare {
     }
 };
 
+class MapIntervalAllocator {
+public:
+    MapIntervalAllocator();
+    ~MapIntervalAllocator();
+
+    MapInterval* Allocate() {
+        if (free_list.empty()) {
+            AllocateNewChunk();
+        }
+        MapInterval* const interval = free_list.back();
+        free_list.pop_back();
+        return interval;
+    }
+
+    void Release(MapInterval* interval) {
+        free_list.push_back(interval);
+    }
+
+private:
+    struct Chunk {
+        std::unique_ptr<Chunk> next;
+        std::array<MapInterval, 0x8000> data;
+    };
+
+    void AllocateNewChunk();
+
+    void FillFreeList(Chunk& chunk);
+
+    std::vector<MapInterval*> free_list;
+    std::unique_ptr<Chunk>* new_chunk = &first_chunk.next;
+
+    Chunk first_chunk;
+};
+
 } // namespace VideoCommon