From ac84ea17a6248062e556065f56a2ae564ff5a303 Mon Sep 17 00:00:00 2001
From: JosJuice <josjuice@gmail.com>
Date: Sat, 21 Jun 2025 20:00:39 +0200
Subject: [PATCH] Memmap: Optimize UpdateLogicalMemory by merging mappings

Instead of creating many 128 KiB mappings, we can create a few large
mappings. On my Windows PC, this speeds up GameCube (FakeVMEM) game boot
times by about 200 ms and Wii game boot times by about 60 ms. Loading
savestates is also faster, by about 45 ms for GameCube (FakeVMEM) games
and 5 ms for Wii games. The impact is presumably smaller on other OSes
because Windows is particularly slow at creating mappings.
---
 Source/Core/Core/HW/Memmap.cpp | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/Source/Core/Core/HW/Memmap.cpp b/Source/Core/Core/HW/Memmap.cpp
index be58fbfc69..675e942009 100644
--- a/Source/Core/Core/HW/Memmap.cpp
+++ b/Source/Core/Core/HW/Memmap.cpp
@@ -248,9 +248,24 @@ void MemoryManager::UpdateLogicalMemory(const PowerPC::BatTable& dbat_table)
     if (dbat_table[i] & PowerPC::BAT_PHYSICAL_BIT)
     {
       u32 logical_address = i << PowerPC::BAT_INDEX_SHIFT;
-      // TODO: Merge adjacent mappings to make this faster.
       u32 logical_size = PowerPC::BAT_PAGE_SIZE;
       u32 translated_address = dbat_table[i] & PowerPC::BAT_RESULT_MASK;
+
+      while (i + 1 < dbat_table.size())
+      {
+        if (!(dbat_table[i + 1] & PowerPC::BAT_PHYSICAL_BIT))
+        {
+          ++i;
+          break;
+        }
+
+        if ((dbat_table[i + 1] & PowerPC::BAT_RESULT_MASK) != translated_address + logical_size)
+          break;
+
+        ++i;
+        logical_size += PowerPC::BAT_PAGE_SIZE;
+      }
+
       for (const auto& physical_region : m_physical_regions)
       {
         if (!physical_region.active)