CPU: Fix loading recompiler-saved states with interpreter

src/core/cpu_core.cpp

@@ -27,6 +27,7 @@
 Log_SetChannel(CPU::Core);
 
 namespace CPU {
+static bool ShouldUseInterpreter();
 static void SetPC(u32 new_pc);
 static void UpdateLoadDelay();
 static void Branch(u32 target);
@@ -66,7 +67,7 @@ static void LogInstruction(u32 bits, u32 pc, bool regs);
 static void HandleWriteSyscall();
 static void HandlePutcSyscall();
 static void HandlePutsSyscall();
-static void ExecuteDebug();
+[[noreturn]] static void ExecuteInterpreter();
 
 template<PGXPMode pgxp_mode, bool debug>
 static void ExecuteInstruction();
@@ -161,7 +162,8 @@ void CPU::Initialize()
   // From nocash spec.
   g_state.cop0_regs.PRID = UINT32_C(0x00000002);
 
-  g_state.use_debug_dispatcher = false;
+  g_state.using_debug_dispatcher = false;
+  g_state.using_interpreter = ShouldUseInterpreter();
   for (BreakpointList& bps : s_breakpoints)
     bps.clear();
   s_breakpoint_counter = 1;
@@ -200,6 +202,7 @@ void CPU::Reset()
 
   ClearICache();
   UpdateMemoryPointers();
+  UpdateDebugDispatcherFlag();
 
   GTE::Reset();
 
@@ -276,8 +279,20 @@ bool CPU::DoState(StateWrapper& sw)
     sw.Do(&g_state.icache_data);
   }
 
+  bool using_interpreter = g_state.using_interpreter;
+  sw.DoEx(&using_interpreter, 67, g_state.using_interpreter);
+
   if (sw.IsReading())
   {
+    // Since the recompilers do not use npc/next_instruction, and the icache emulation doesn't actually fill the data,
+    // only the tags, if we save state with the recompiler, then load state with the interpreter, we're most likely
+    // going to crash. Clear both in the case that we are switching.
+    if (using_interpreter != g_state.using_interpreter)
+    {
+      WARNING_LOG("Current execution mode does not match save state. Resetting icache state.");
+      ExecutionModeChanged();
+    }
+
     UpdateMemoryPointers();
     g_state.gte_completion_tick = 0;
   }
@@ -285,6 +300,12 @@ bool CPU::DoState(StateWrapper& sw)
   return !sw.HasError();
 }
 
+ALWAYS_INLINE_RELEASE bool CPU::ShouldUseInterpreter()
+{
+  // Currently, any breakpoints require the interpreter.
+  return (g_settings.cpu_execution_mode == CPUExecutionMode::Interpreter || g_state.using_debug_dispatcher);
+}
+
 ALWAYS_INLINE_RELEASE void CPU::SetPC(u32 new_pc)
 {
   DebugAssert(Common::IsAlignedPow2(new_pc, 4));
@@ -1983,11 +2004,16 @@ bool CPU::UpdateDebugDispatcherFlag()
   const bool use_debug_dispatcher =
     has_any_breakpoints || has_cop0_breakpoints || s_trace_to_log ||
     (g_settings.cpu_execution_mode == CPUExecutionMode::Interpreter && g_settings.bios_tty_logging);
-  if (use_debug_dispatcher == g_state.use_debug_dispatcher)
+  if (use_debug_dispatcher == g_state.using_debug_dispatcher)
     return false;
 
   DEV_LOG("{} debug dispatcher", use_debug_dispatcher ? "Now using" : "No longer using");
-  g_state.use_debug_dispatcher = use_debug_dispatcher;
+  g_state.using_debug_dispatcher = use_debug_dispatcher;
+
+  // Switching to interpreter?
+  if (g_state.using_interpreter != ShouldUseInterpreter())
+    ExecutionModeChanged();
+
   return true;
 }
 
@@ -2350,7 +2376,9 @@ template<PGXPMode pgxp_mode, bool debug>
   }
 }
 
-void CPU::ExecuteDebug()
+void CPU::ExecuteInterpreter()
+{
+  if (g_state.using_debug_dispatcher)
   {
     if (g_settings.gpu_pgxp_enable)
     {
@@ -2364,45 +2392,7 @@ void CPU::ExecuteDebug()
       ExecuteImpl<PGXPMode::Disabled, true>();
     }
   }
-
-void CPU::Execute()
-{
-  const CPUExecutionMode exec_mode = g_settings.cpu_execution_mode;
-  const bool use_debug_dispatcher = g_state.use_debug_dispatcher;
-  if (fastjmp_set(&s_jmp_buf) != 0)
-  {
-    // Before we return, set npc to pc so that we can switch from recs to int.
-    // We'll also need to fetch the next instruction to execute.
-    if (exec_mode != CPUExecutionMode::Interpreter && !use_debug_dispatcher)
-    {
-      if (!SafeReadInstruction(g_state.pc, &g_state.next_instruction.bits)) [[unlikely]]
-      {
-        g_state.next_instruction.bits = 0;
-        ERROR_LOG("Failed to read current instruction from 0x{:08X}", g_state.pc);
-      }
-
-      g_state.npc = g_state.pc + sizeof(Instruction);
-    }
-
-    return;
-  }
-
-  if (use_debug_dispatcher)
-  {
-    ExecuteDebug();
-    return;
-  }
-
-  switch (exec_mode)
-  {
-    case CPUExecutionMode::Recompiler:
-    case CPUExecutionMode::CachedInterpreter:
-    case CPUExecutionMode::NewRec:
-      CodeCache::Execute();
-      break;
-
-    case CPUExecutionMode::Interpreter:
-    default:
+  else
   {
     if (g_settings.gpu_pgxp_enable)
     {
@@ -2416,8 +2406,17 @@ void CPU::Execute()
       ExecuteImpl<PGXPMode::Disabled, false>();
     }
   }
-    break;
 }
+
+void CPU::Execute()
+{
+  if (fastjmp_set(&s_jmp_buf) != 0)
+    return;
+
+  if (g_state.using_interpreter)
+    ExecuteInterpreter();
+  else
+    CodeCache::Execute();
 }
 
 void CPU::SetSingleStepFlag()
@@ -2572,8 +2571,36 @@ void CPU::UpdateMemoryPointers()
 
 void CPU::ExecutionModeChanged()
 {
+  const bool prev_interpreter = g_state.using_interpreter;
+
+  UpdateDebugDispatcherFlag();
+
+  // Clear out bus errors in case only memory exceptions are toggled on.
   g_state.bus_error = false;
-  if (UpdateDebugDispatcherFlag())
+
+  // Have to clear out the icache too, only the tags are valid in the recs.
+  ClearICache();
+
+  // Switching to interpreter?
+  g_state.using_interpreter = ShouldUseInterpreter();
+  if (g_state.using_interpreter != prev_interpreter && !prev_interpreter)
+  {
+    // Before we return, set npc to pc so that we can switch from recs to int.
+    // We'll also need to fetch the next instruction to execute.
+    if (!SafeReadInstruction(g_state.pc, &g_state.next_instruction.bits)) [[unlikely]]
+    {
+      g_state.next_instruction.bits = 0;
+      ERROR_LOG("Failed to read current instruction from 0x{:08X}", g_state.pc);
+    }
+
+    g_state.npc = g_state.pc + sizeof(Instruction);
+  }
+
+  // Wipe out code cache when switching back to recompiler.
+  if (!g_state.using_interpreter && prev_interpreter)
+    CPU::CodeCache::Reset();
+
+  UpdateDebugDispatcherFlag();
   System::InterruptExecution();
 }
 

src/core/cpu_core.h

@@ -110,8 +110,9 @@ struct State
   // GTE registers are stored here so we can access them on ARM with a single instruction
   GTE::Regs gte_regs = {};
 
-  // 4 bytes of padding here on x64
-  bool use_debug_dispatcher = false;
+  // 2 bytes of padding here on x64
+  bool using_interpreter = false;
+  bool using_debug_dispatcher = false;
 
   void* fastmem_base = nullptr;
   void** memory_handlers = nullptr;

src/core/cpu_recompiler_code_generator.cpp

@@ -2843,7 +2843,7 @@ bool CodeGenerator::Compile_cop0(Instruction instruction, const CodeCache::Instr
 
             // update dispatcher flag, if enabled, exit block
             EmitFunctionCall(nullptr, &UpdateDebugDispatcherFlag);
-            EmitLoadCPUStructField(dcic_value.GetHostRegister(), RegSize_8, OFFSETOF(State, use_debug_dispatcher));
+            EmitLoadCPUStructField(dcic_value.GetHostRegister(), RegSize_8, OFFSETOF(State, using_debug_dispatcher));
             EmitBranchIfBitClear(dcic_value.GetHostRegister(), RegSize_8, 0, &not_enabled);
 
             m_register_cache.UninhibitAllocation();

src/core/imgui_overlays.cpp

@@ -6,6 +6,7 @@
 #include "imgui_overlays.h"
 #include "cdrom.h"
 #include "controller.h"
+#include "cpu_core_private.h"
 #include "dma.h"
 #include "fullscreen_ui.h"
 #include "gpu.h"
@@ -320,9 +321,9 @@ void ImGuiManager::DrawPerformanceOverlay()
                   System::GetMaximumFrameTime());
       DRAW_LINE(fixed_font, text, IM_COL32(255, 255, 255, 255));
 
-      if (g_settings.cpu_overclock_active ||
-          (g_settings.cpu_execution_mode != CPUExecutionMode::Recompiler || g_settings.cpu_recompiler_icache ||
-           g_settings.cpu_recompiler_memory_exceptions))
+      if (g_settings.cpu_overclock_active || CPU::g_state.using_interpreter ||
+          g_settings.cpu_execution_mode != CPUExecutionMode::Recompiler || g_settings.cpu_recompiler_icache ||
+          g_settings.cpu_recompiler_memory_exceptions)
       {
         first = true;
         text.assign("CPU[");
@@ -331,7 +332,7 @@ void ImGuiManager::DrawPerformanceOverlay()
           text.append_format("{}", g_settings.GetCPUOverclockPercent());
           first = false;
         }
-        if (g_settings.cpu_execution_mode == CPUExecutionMode::Interpreter)
+        if (CPU::g_state.using_interpreter)
         {
           text.append_format("{}{}", first ? "" : "/", "I");
           first = false;

src/core/save_state_version.h

@@ -5,7 +5,7 @@
 #include "types.h"
 
 static constexpr u32 SAVE_STATE_MAGIC = 0x43435544;
-static constexpr u32 SAVE_STATE_VERSION = 66;
+static constexpr u32 SAVE_STATE_VERSION = 67;
 static constexpr u32 SAVE_STATE_MINIMUM_VERSION = 42;
 
 static_assert(SAVE_STATE_VERSION >= SAVE_STATE_MINIMUM_VERSION);

src/core/system.cpp

@@ -4012,7 +4012,6 @@ void System::CheckForSettingsChanges(const Settings& old_settings)
         CPU::CodeCache::Shutdown();
       if (g_settings.cpu_execution_mode != CPUExecutionMode::Interpreter)
         CPU::CodeCache::Initialize();
-      CPU::ClearICache();
     }
 
     if (CPU::CodeCache::IsUsingAnyRecompiler() &&
@@ -4025,10 +4024,6 @@ void System::CheckForSettingsChanges(const Settings& old_settings)
                               TRANSLATE_STR("OSDMessage", "Recompiler options changed, flushing all blocks."),
                               Host::OSD_INFO_DURATION);
       CPU::ExecutionModeChanged();
-      CPU::CodeCache::Reset();
-
-      if (g_settings.cpu_recompiler_icache != old_settings.cpu_recompiler_icache)
-        CPU::ClearICache();
     }
     else if (g_settings.cpu_execution_mode == CPUExecutionMode::Interpreter &&
              g_settings.bios_tty_logging != old_settings.bios_tty_logging)