On x86, disabling fastmem isn't enough actually.

Without fastmem, the JIT code still does an inline check for RAM
addresses.  With watchpoints we have to disable that too.  (Hardware
watchpoints would avoid all the slow, but be complicated to implement
and limited in number - I doubt most people debugging games care much if
they run slower.)

With this change and watchpoints enabled, Melee runs at no more than 40%
speed, despite running at full speed without them.  Oh well.  Better
works slowly than doesn't bloody work.

Incidentally, I'm getting an unrelated crash in
PowerPC::HostIsRAMAddress when shutting down a game.  This code sucks.

Source/Core/Core/PowerPC/JitCommon/JitBase.cpp

@@ -90,4 +90,6 @@ void JitBase::UpdateMemoryOptions()
 	             !any_watchpoints;
 	jo.memcheck = SConfig::GetInstance().m_LocalCoreStartupParameter.bMMU ||
 	              any_watchpoints;
+	jo.alwaysUseMemFuncs = any_watchpoints;
+
 }

Source/Core/Core/PowerPC/JitCommon/JitBase.h

@@ -63,6 +63,7 @@ protected:
 		bool accurateSinglePrecision;
 		bool fastmem;
 		bool memcheck;
+		bool alwaysUseMemFuncs;
 	};
 	struct JitState
 	{

Source/Core/Core/PowerPC/JitCommon/Jit_Util.cpp

@@ -349,14 +349,17 @@ void EmuCodeBlock::SafeLoadToReg(X64Reg reg_value, const Gen::OpArg & opAddress,
 		LEA(32, RSCRATCH, MDisp(opAddress.GetSimpleReg(), offset));
 	}
 
-	FixupBranch slow, exit;
-	slow = CheckIfSafeAddress(R(reg_value), reg_addr, registersInUse, mem_mask);
-	UnsafeLoadToReg(reg_value, R(reg_addr), accessSize, 0, signExtend);
-	if (farcode.Enabled())
-		SwitchToFarCode();
-	else
-		exit = J(true);
-	SetJumpTarget(slow);
+	FixupBranch exit;
+	if (!jit->jo.alwaysUseMemFuncs)
+	{
+		FixupBranch slow = CheckIfSafeAddress(R(reg_value), reg_addr, registersInUse, mem_mask);
+		UnsafeLoadToReg(reg_value, R(reg_addr), accessSize, 0, signExtend);
+		if (farcode.Enabled())
+			SwitchToFarCode();
+		else
+			exit = J(true);
+		SetJumpTarget(slow);
+	}
 	size_t rsp_alignment = (flags & SAFE_LOADSTORE_NO_PROLOG) ? 8 : 0;
 	ABI_PushRegistersAndAdjustStack(registersInUse, rsp_alignment);
 	switch (accessSize)
@@ -387,12 +390,15 @@ void EmuCodeBlock::SafeLoadToReg(X64Reg reg_value, const Gen::OpArg & opAddress,
 		MOVZX(64, accessSize, reg_value, R(ABI_RETURN));
 	}
 
-	if (farcode.Enabled())
+	if (!jit->jo.alwaysUseMemFuncs)
 	{
-		exit = J(true);
-		SwitchToNearCode();
+		if (farcode.Enabled())
+		{
+			exit = J(true);
+			SwitchToNearCode();
+		}
+		SetJumpTarget(exit);
 	}
-	SetJumpTarget(exit);
 }
 
 static OpArg SwapImmediate(int accessSize, OpArg reg_value)

Source/Core/Core/PowerPC/MMU.cpp

@@ -629,6 +629,10 @@ std::string HostGetString(u32 address, size_t size)
 
 bool IsOptimizableRAMAddress(const u32 address)
 {
+#ifdef ENABLE_MEM_CHECK
+	return false;
+#endif
+
 	if (!UReg_MSR(MSR).DR)
 		return false;
 
@@ -752,6 +756,10 @@ void ClearCacheLine(const u32 address)
 
 u32 IsOptimizableMMIOAccess(u32 address, u32 accessSize)
 {
+#ifdef ENABLE_MEM_CHECK
+	return 0;
+#endif
+
 	if (!UReg_MSR(MSR).DR)
 		return 0;
 
@@ -767,6 +775,10 @@ u32 IsOptimizableMMIOAccess(u32 address, u32 accessSize)
 
 bool IsOptimizableGatherPipeWrite(u32 address)
 {
+#ifdef ENABLE_MEM_CHECK
+	return false;
+#endif
+
 	if (!UReg_MSR(MSR).DR)
 		return false;