VMManager: Make EE rec toggles reliable

Before, it'd swap out the Cpu while it was executing...

pcsx2/Config.h

@@ -393,6 +393,8 @@ struct Pcsx2Config
 		void LoadSave(SettingsWrapper& wrap);
 		void ApplySanityCheck();
 
+		bool CpusChanged(const CpuOptions& right) const;
+
 		bool operator==(const CpuOptions& right) const
 		{
 			return OpEqu(sseMXCSR) && OpEqu(sseVUMXCSR) && OpEqu(Recompiler);

pcsx2/Pcsx2Config.cpp

@@ -224,6 +224,14 @@ void Pcsx2Config::RecompilerOptions::LoadSave(SettingsWrapper& wrap)
 	SettingsWrapBitBool(PreBlockCheckIOP);
 }
 
+bool Pcsx2Config::CpuOptions::CpusChanged(const CpuOptions& right) const
+{
+	return (Recompiler.EnableEE != right.Recompiler.EnableEE ||
+			Recompiler.EnableIOP != right.Recompiler.EnableIOP ||
+			Recompiler.EnableVU0 != right.Recompiler.EnableVU0 ||
+			Recompiler.EnableVU1 != right.Recompiler.EnableVU1);
+}
+
 Pcsx2Config::CpuOptions::CpuOptions()
 {
 	sseMXCSR.bitmask = DEFAULT_sseMXCSR;

pcsx2/System.cpp

@@ -592,7 +592,10 @@ void SysCpuProviderPack::ApplyConfig() const
 // Use this method to reset the recs when important global pointers like the MTGS are re-assigned.
 void SysClearExecutionCache()
 {
+	// Done by VMManager in Qt.
+#ifndef PCSX2_CORE
 	GetCpuProviders().ApplyConfig();
+#endif
 
 	Cpu->Reset();
 	psxCpu->Reset();

pcsx2/VMManager.cpp

@@ -96,6 +96,7 @@ static std::unique_ptr<INISettingsInterface> s_game_settings_interface;
 static u64 s_emu_thread_affinity;
 
 static std::atomic<VMState> s_state{VMState::Shutdown};
+static std::atomic_bool s_cpu_implementation_changed{false};
 
 static std::mutex s_info_mutex;
 static std::string s_disc_path;
@@ -757,6 +758,8 @@ bool VMManager::Initialize(const VMBootParameters& boot_params)
 	s_mxcsr_saved = static_cast<u32>(a64_getfpcr());
 #endif
 
+	s_cpu_implementation_changed.store(false);
+	s_cpu_provider_pack->ApplyConfig();
 	SetCPUState(EmuConfig.Cpu.sseMXCSR, EmuConfig.Cpu.sseVUMXCSR);
 	SysClearExecutionCache();
 	memBindConditionalHandlers();
@@ -1039,6 +1042,15 @@ bool VMManager::IsGSDumpFileName(const std::string& path)
 
 void VMManager::Execute()
 {
+	// Check for interpreter<->recompiler switches.
+	if (s_cpu_implementation_changed.exchange(false))
+	{
+		// We need to switch the cpus out, and reset the new ones if so.
+		s_cpu_provider_pack->ApplyConfig();
+		SysClearExecutionCache();
+	}
+
+	// Execute until we're asked to stop.
 	Cpu->Execute();
 }
 
@@ -1058,7 +1070,7 @@ const std::string& VMManager::Internal::GetElfOverride()
 
 bool VMManager::Internal::IsExecutionInterrupted()
 {
-	return s_state.load() != VMState::Running;
+	return s_state.load() != VMState::Running || s_cpu_implementation_changed.load();
 }
 
 void VMManager::Internal::GameStartingOnCPUThread()
@@ -1098,6 +1110,15 @@ void VMManager::CheckForCPUConfigChanges(const Pcsx2Config& old_config)
 	SetCPUState(EmuConfig.Cpu.sseMXCSR, EmuConfig.Cpu.sseVUMXCSR);
 	SysClearExecutionCache();
 	memBindConditionalHandlers();
+
+	// did we toggle recompilers?
+	if (EmuConfig.Cpu.CpusChanged(old_config.Cpu))
+	{
+		// This has to be done asynchronously, since we're still executing the
+		// cpu when this function is called. Break the execution as soon as
+		// possible and reset next time we're called.
+		s_cpu_implementation_changed.store(true);
+	}
 }
 
 void VMManager::CheckForGSConfigChanges(const Pcsx2Config& old_config)