Patches for Resident Evil 2/3 audio issues

These games are erroneously zeroing buffers before they can be fully copied to ARAM by DMA. The responsible memset() calls are followed by a call to DVDRead() which issues dcbi instructions that effectively cancel the memset() on real hardware. Because Dolphin lacks dcache emulation, the effects of the memset() calls are observed, which causes missing audio.

In a comment on the original bug, phire noted that the issue can be corrected by simply nop'ing out the offending memset() calls. Because the games dynamically load different .rel executables based on the character and/or language, the addresses of these calls can vary.

To deal generally with the problem of code being dynamically loaded to fixed, known addresses, the patch engine is extended to support conditional patches which require a match against a known value. This sort of thing is already achievable with Action Replay/Gecko codes, but their use depends on enabling cheats globally in Dolphin, which is not a prerequisite shared by patches.

Patches are included for every region, character, and language combination. They are enabled by default.

The end result is an approximation of the games' behavior on real hardware without the associated complexity of proper dcache emulation.

https://bugs.dolphin-emu.org/issues/9840

4 files changed, 88 insertions, 44 deletions

diff --git a/Source/Core/Core/PatchEngine.cpp b/Source/Core/Core/PatchEngine.cpp
index 4f4daafcd7..a3b13c14d3 100644
--- a/Source/Core/Core/PatchEngine.cpp
+++ b/Source/Core/Core/PatchEngine.cpp
@@ -90,6 +90,11 @@ void LoadPatchSection(const std::string& section, std::vector<Patch>& patches, I
           bool success = true;
           success &= TryParse(items[0], &pE.address);
           success &= TryParse(items[2], &pE.value);
+          if (items.size() >= 4)
+          {
+            success &= TryParse(items[3], &pE.comparand);
+            pE.conditional = true;
+          }
 
           const auto iter =
               std::find(s_patch_type_strings.begin(), s_patch_type_strings.end(), items[1]);
@@ -184,16 +189,20 @@ static void ApplyPatches(const std::vector<Patch>& patches)
       {
         u32 addr = entry.address;
         u32 value = entry.value;
+        u32 comparand = entry.comparand;
         switch (entry.type)
         {
         case PatchType::Patch8Bit:
-          PowerPC::HostWrite_U8(static_cast<u8>(value), addr);
+          if (!entry.conditional || PowerPC::HostRead_U8(addr) == static_cast<u8>(comparand))
+            PowerPC::HostWrite_U8(static_cast<u8>(value), addr);
           break;
         case PatchType::Patch16Bit:
-          PowerPC::HostWrite_U16(static_cast<u16>(value), addr);
+          if (!entry.conditional || PowerPC::HostRead_U16(addr) == static_cast<u16>(comparand))
+            PowerPC::HostWrite_U16(static_cast<u16>(value), addr);
           break;
         case PatchType::Patch32Bit:
-          PowerPC::HostWrite_U32(value, addr);
+          if (!entry.conditional || PowerPC::HostRead_U32(addr) == comparand)
+            PowerPC::HostWrite_U32(value, addr);
           break;
         default:
           // unknown patchtype
diff --git a/Source/Core/Core/PatchEngine.h b/Source/Core/Core/PatchEngine.h
index a496f04936..490fb2e646 100644
--- a/Source/Core/Core/PatchEngine.h
+++ b/Source/Core/Core/PatchEngine.h
@@ -27,6 +27,8 @@ struct PatchEntry
   PatchType type = PatchType::Patch8Bit;
   u32 address = 0;
   u32 value = 0;
+  u32 comparand = 0;
+  bool conditional = false;
 };
 
 struct Patch
diff --git a/Source/Core/DolphinQt/Config/NewPatchDialog.cpp b/Source/Core/DolphinQt/Config/NewPatchDialog.cpp
index b0f45afc49..95d0eb7621 100644
--- a/Source/Core/DolphinQt/Config/NewPatchDialog.cpp
+++ b/Source/Core/DolphinQt/Config/NewPatchDialog.cpp
@@ -4,6 +4,7 @@
 
 #include "DolphinQt/Config/NewPatchDialog.h"
 
+#include <QCheckBox>
 #include <QDialogButtonBox>
 #include <QGridLayout>
 #include <QGroupBox>
@@ -84,6 +85,25 @@ void NewPatchDialog::AddEntry()
   m_entry_layout->addWidget(CreateEntry(m_patch.entries[m_patch.entries.size() - 1]));
 }
 
+static u32 OnTextEdited(QLineEdit* edit, const QString& text)
+{
+  bool okay = false;
+  u32 value = text.toUInt(&okay, 16);
+
+  QFont font;
+  QPalette palette;
+
+  font.setBold(!okay);
+
+  if (!okay)
+    palette.setColor(QPalette::Text, Qt::red);
+
+  edit->setFont(font);
+  edit->setPalette(palette);
+
+  return value;
+}
+
 static bool PatchEq(const PatchEngine::PatchEntry& a, const PatchEngine::PatchEntry& b)
 {
   if (a.address != b.address)
@@ -95,6 +115,12 @@ static bool PatchEq(const PatchEngine::PatchEntry& a, const PatchEngine::PatchEn
   if (a.value != b.value)
     return false;
 
+  if (a.comparand != b.comparand)
+    return false;
+
+  if (a.conditional != b.conditional)
+    return false;
+
   return true;
 }
 
@@ -115,56 +141,41 @@ QGroupBox* NewPatchDialog::CreateEntry(PatchEngine::PatchEntry& entry)
   type_layout->addWidget(dword);
   type->setLayout(type_layout);
 
-  auto* offset = new QLineEdit;
+  auto* address = new QLineEdit;
   auto* value = new QLineEdit;
+  auto* comparand = new QLineEdit;
 
-  m_edits.push_back(offset);
+  m_edits.push_back(address);
   m_edits.push_back(value);
+  m_edits.push_back(comparand);
+
+  auto* conditional = new QCheckBox(tr("Conditional"));
+  auto* comparand_label = new QLabel(tr("Comparand:"));
 
   auto* layout = new QGridLayout;
   layout->addWidget(type, 0, 0, 1, -1);
-  layout->addWidget(new QLabel(tr("Offset:")), 1, 0);
-  layout->addWidget(offset, 1, 1);
+  layout->addWidget(new QLabel(tr("Address:")), 1, 0);
+  layout->addWidget(address, 1, 1);
   layout->addWidget(new QLabel(tr("Value:")), 2, 0);
   layout->addWidget(value, 2, 1);
-  layout->addWidget(remove, 3, 0, 1, -1);
+  layout->addWidget(conditional, 3, 0, 1, -1);
+  layout->addWidget(comparand_label, 4, 0);
+  layout->addWidget(comparand, 4, 1);
+  layout->addWidget(remove, 5, 0, 1, -1);
   box->setLayout(layout);
 
-  connect(offset, qOverload<const QString&>(&QLineEdit::textEdited),
-          [&entry, offset](const QString& text) {
-            bool okay = true;
-            entry.address = text.toUInt(&okay, 16);
-
-            QFont font;
-            QPalette palette;
-
-            font.setBold(!okay);
-
-            if (!okay)
-              palette.setColor(QPalette::Text, Qt::red);
-
-            offset->setFont(font);
-            offset->setPalette(palette);
-          });
+  connect(address, qOverload<const QString&>(&QLineEdit::textEdited),
+          [&entry, address](const QString& text) { entry.address = OnTextEdited(address, text); });
 
   connect(value, qOverload<const QString&>(&QLineEdit::textEdited),
-          [&entry, value](const QString& text) {
-            bool okay;
-            entry.value = text.toUInt(&okay, 16);
+          [&entry, value](const QString& text) { entry.value = OnTextEdited(value, text); });
 
-            QFont font;
-            QPalette palette;
-
-            font.setBold(!okay);
-
-            if (!okay)
-              palette.setColor(QPalette::Text, Qt::red);
-
-            value->setFont(font);
-            value->setPalette(palette);
+  connect(comparand, qOverload<const QString&>(&QLineEdit::textEdited),
+          [&entry, comparand](const QString& text) {
+            entry.comparand = OnTextEdited(comparand, text);
           });
 
-  connect(remove, &QPushButton::clicked, [this, box, offset, value, entry] {
+  connect(remove, &QPushButton::clicked, [this, box, address, value, comparand, entry] {
     if (m_patch.entries.size() > 1)
     {
       box->setVisible(false);
@@ -175,9 +186,9 @@ QGroupBox* NewPatchDialog::CreateEntry(PatchEngine::PatchEntry& entry)
           std::find_if(m_patch.entries.begin(), m_patch.entries.end(),
                        [entry](const PatchEngine::PatchEntry& e) { return PatchEq(e, entry); }));
 
-      const auto it =
-          std::remove_if(m_edits.begin(), m_edits.end(), [offset, value](QLineEdit* line_edit) {
-            return line_edit == offset || line_edit == value;
+      const auto it = std::remove_if(
+          m_edits.begin(), m_edits.end(), [address, value, comparand](QLineEdit* line_edit) {
+            return line_edit == address || line_edit == value || line_edit == comparand;
           });
       m_edits.erase(it, m_edits.end());
     }
@@ -202,8 +213,19 @@ QGroupBox* NewPatchDialog::CreateEntry(PatchEngine::PatchEntry& entry)
   word->setChecked(entry.type == PatchEngine::PatchType::Patch16Bit);
   dword->setChecked(entry.type == PatchEngine::PatchType::Patch32Bit);
 
-  offset->setText(QStringLiteral("%1").arg(entry.address, 8, 16, QLatin1Char('0')));
+  connect(conditional, &QCheckBox::toggled, [&entry, comparand_label, comparand](bool checked) {
+    entry.conditional = checked;
+    comparand_label->setVisible(checked);
+    comparand->setVisible(checked);
+  });
+
+  conditional->setChecked(entry.conditional);
+  comparand_label->setVisible(entry.conditional);
+  comparand->setVisible(entry.conditional);
+
+  address->setText(QStringLiteral("%1").arg(entry.address, 8, 16, QLatin1Char('0')));
   value->setText(QStringLiteral("%1").arg(entry.value, 8, 16, QLatin1Char('0')));
+  comparand->setText(QStringLiteral("%1").arg(entry.comparand, 8, 16, QLatin1Char('0')));
 
   return box;
 }
diff --git a/Source/Core/DolphinQt/Config/PatchesWidget.cpp b/Source/Core/DolphinQt/Config/PatchesWidget.cpp
index 43dd4a415e..8628f1997a 100644
--- a/Source/Core/DolphinQt/Config/PatchesWidget.cpp
+++ b/Source/Core/DolphinQt/Config/PatchesWidget.cpp
@@ -8,6 +8,8 @@
 #include <QListWidget>
 #include <QPushButton>
 
+#include <fmt/format.h>
+
 #include "Common/FileUtil.h"
 #include "Common/IniFile.h"
 #include "Common/StringUtil.h"
@@ -143,8 +145,17 @@ void PatchesWidget::SavePatches()
 
     for (const auto& entry : patch.entries)
     {
-      lines.emplace_back(StringFromFormat("0x%08X:%s:0x%08X", entry.address,
-                                          PatchEngine::PatchTypeAsString(entry.type), entry.value));
+      if (!entry.conditional)
+      {
+        lines.emplace_back(fmt::format("0x{:08X}:{}:0x{:08X}", entry.address,
+                                       PatchEngine::PatchTypeAsString(entry.type), entry.value));
+      }
+      else
+      {
+        lines.emplace_back(fmt::format("0x{:08X}:{}:0x{:08X}:0x{:08X}", entry.address,
+                                       PatchEngine::PatchTypeAsString(entry.type), entry.value,
+                                       entry.comparand));
+      }
     }
   }