Hook the Gecko codehandler to invalidate the icache.

The codehandler is broken and does not do this itself.  This is a hack,
but a lot simpler than the alternatives.

Source/Core/Core/Src/Boot/Boot.cpp

@@ -192,6 +192,10 @@ bool CBoot::BootUp()
 		Memory::WriteBigEData(stubstr, 0x80001804, 8);
 	}
 
+	// Not part of the binary itself, but either we or Gecko OS might insert
+	// this, and it doesn't clear the icache properly.
+	HLE::Patch(0x800018a8, "GeckoCodehandler");
+
 	g_symbolDB.Clear();
 	VideoInterface::Preset(_StartupPara.bNTSC);
 	switch (_StartupPara.m_BootType)

Source/Core/Core/Src/HLE/HLE.cpp

@@ -63,6 +63,7 @@ static const SPatch OSPatches[] =
 	{ "___blank(char *,...)",	HLE_OS::HLE_GeneralDebugPrint, HLE_HOOK_REPLACE, HLE_TYPE_DEBUG }, // used for early init things (normally)
 	{ "___blank",			HLE_OS::HLE_GeneralDebugPrint, HLE_HOOK_REPLACE, HLE_TYPE_DEBUG },
 	{ "__write_console",		HLE_OS::HLE_write_console, HLE_HOOK_REPLACE, HLE_TYPE_DEBUG }, // used by sysmenu (+more?)
+	{ "GeckoCodehandler",		HLE_Misc::HLEGeckoCodehandler, HLE_HOOK_START, HLE_TYPE_GENERIC },
 };
 
 static const SPatch OSBreakPoints[] =

Source/Core/Core/Src/HLE/HLE_Misc.cpp

@@ -17,6 +17,7 @@
 #include "IPC_HLE/WII_IPC_HLE_Device_usb.h"
 #include "HLE.h"
 #include "PowerPC/PPCAnalyst.h"
+#include "PowerPC/PPCCache.h"
 #include "PowerPC/SignatureDB.h"
 #include "PowerPC/PPCSymbolDB.h"
 #include "CommonPaths.h"
@@ -242,4 +243,26 @@ void OSBootDol()
 	NPC = PC;
 }
 
+void HLEGeckoCodehandler()
+{
+	// Work around the codehandler not properly invalidating the icache, but
+	// only the first few frames.
+	// (Project M uses a conditional to only apply patches after something has
+	// been read into memory, or such, so we do the first 5 frames.  More
+	// robust alternative would be to actually detect memory writes, but that
+	// would be even uglier.)
+	u32 magic = 0xd01f1bad;
+	u32 existing = Memory::Read_U32(0x80001800);
+	if (existing - magic == 5)
+	{
+		return;
+	}
+	else if(existing - magic > 5)
+	{
+		existing = magic;
+	}
+	Memory::Write_U32(existing + 1, 0x80001800);
+	PowerPC::ppcState.iCache.Reset();
+}
+
 }

Source/Core/Core/Src/HLE/HLE_Misc.h

@@ -12,6 +12,7 @@ namespace HLE_Misc
 	void HBReload();
 	void OSBootDol();
 	void OSGetResetCode();
+	void HLEGeckoCodehandler();
 }
 
 #endif