Use a fake exception to exit early in case of memory breakpoints.

Change TMemCheck::Action to return whether to break rather than calling
PPCDebugInterface::BreakNow, as this simplified the implementation; then
remove said method, as that was its only caller.  One "interface" method
down, many to go...

Source/Core/Common/BreakPoints.cpp

@@ -207,7 +207,7 @@ TMemCheck *MemChecks::GetMemCheck(u32 address)
 	return nullptr;
 }
 
-void TMemCheck::Action(DebugInterface *debug_interface, u32 iValue, u32 addr, bool write, int size, u32 pc)
+bool TMemCheck::Action(DebugInterface *debug_interface, u32 iValue, u32 addr, bool write, int size, u32 pc)
 {
 	if ((write && OnWrite) || (!write && OnRead))
 	{
@@ -220,9 +220,9 @@ void TMemCheck::Action(DebugInterface *debug_interface, u32 iValue, u32 addr, bo
 				);
 		}
 
-		if (Break)
+		return true;
-			debug_interface->BreakNow();
 	}
+	return false;
 }
 
 

Source/Core/Common/BreakPoints.h

@@ -40,7 +40,8 @@ struct TMemCheck
 
 	u32 numHits;
 
-	void Action(DebugInterface *dbg_interface, u32 _iValue, u32 addr,
+	// returns whether to break
+	bool Action(DebugInterface *dbg_interface, u32 _iValue, u32 addr,
 	            bool write, int size, u32 pc);
 };
 

Source/Core/Common/DebugInterface.h

@@ -30,7 +30,6 @@ public:
 	virtual void SetPC(unsigned int /*address*/) {}
 	virtual void Step() {}
 	virtual void RunToBreakpoint() {}
-	virtual void BreakNow() {}
 	virtual void InsertBLR(unsigned int /*address*/, unsigned int /*value*/) {}
 	virtual int GetColor(unsigned int /*address*/){return 0xFFFFFFFF;}
 	virtual std::string GetDescription(unsigned int /*address*/) = 0;

Source/Core/Core/Debugger/PPCDebugInterface.cpp

@@ -169,11 +169,6 @@ void PPCDebugInterface::InsertBLR(unsigned int address, unsigned int value)
 	PowerPC::HostWrite_U32(value, address);
 }
 
-void PPCDebugInterface::BreakNow()
-{
-	CCPU::Break();
-}
-
 
 // =======================================================
 // Separate the blocks with colors.

Source/Core/Core/Debugger/PPCDebugInterface.h

@@ -39,7 +39,6 @@ public:
 	virtual unsigned int GetPC() override;
 	virtual void SetPC(unsigned int address) override;
 	virtual void Step() override {}
-	virtual void BreakNow() override;
 	virtual void RunToBreakpoint() override;
 	virtual void InsertBLR(unsigned int address, unsigned int value) override;
 	virtual int GetColor(unsigned int address) override;

Source/Core/Core/HW/CPU.cpp

@@ -13,6 +13,7 @@
 #include "Core/Movie.h"
 #include "Core/HW/CPU.h"
 #include "Core/HW/DSP.h"
+#include "Core/HW/Memmap.h"
 #include "Core/PowerPC/PowerPC.h"
 #include "VideoCommon/VideoBackendBase.h"
 
@@ -117,7 +118,14 @@ void CCPU::EnableStepping(const bool _bStepping)
 	{
 		// SingleStep so that the "continue", "step over" and "step out" debugger functions
 		// work when the PC is at a breakpoint at the beginning of the block
-		if (PowerPC::breakpoints.IsAddressBreakPoint(PC) && PowerPC::GetMode() != PowerPC::MODE_INTERPRETER)
+		// If watchpoints are enabled, any instruction could be a breakpoint.
+		bool could_be_bp;
+#ifdef ENABLE_MEM_CHECK
+		could_be_bp = true;
+#else
+		could_be_bp = PowerPC::breakpoints.IsAddressBreakPoint(PC);
+#endif
+		if (could_be_bp && PowerPC::GetMode() != PowerPC::MODE_INTERPRETER)
 		{
 			PowerPC::CoreMode oldMode = PowerPC::GetMode();
 			PowerPC::SetMode(PowerPC::MODE_INTERPRETER);

Source/Core/Core/PowerPC/Gekko.h

@@ -831,7 +831,9 @@ enum
 	EXCEPTION_ALIGNMENT           = 0x00000020,
 	EXCEPTION_FPU_UNAVAILABLE     = 0x00000040,
 	EXCEPTION_PROGRAM             = 0x00000080,
-	EXCEPTION_PERFORMANCE_MONITOR = 0x00000100
+	EXCEPTION_PERFORMANCE_MONITOR = 0x00000100,
+
+	EXCEPTION_FAKE_MEMCHECK_HIT   = 0x00000200,
 };
 
 inline s32 SignExt16(s16 x) {return (s32)(s16)x;}

Source/Core/Core/PowerPC/MMU.cpp

@@ -21,6 +21,7 @@
 
 #include "Core/ConfigManager.h"
 #include "Core/Core.h"
+#include "Core/HW/CPU.h"
 #include "Core/HW/GPFifo.h"
 #include "Core/HW/Memmap.h"
 #include "Core/HW/MMIO.h"
@@ -455,8 +456,25 @@ static __forceinline void Memcheck(u32 address, u32 var, bool write, int size)
 	TMemCheck *mc = PowerPC::memchecks.GetMemCheck(address);
 	if (mc)
 	{
+		if (CCPU::IsStepping())
+		{
+			// Disable when stepping so that resume works.
+			return;
+		}
 		mc->numHits++;
-		mc->Action(&PowerPC::debug_interface, var, address, write, size, PC);
+		bool pause = mc->Action(&PowerPC::debug_interface, var, address, write, size, PC);
+		if (pause)
+		{
+			CCPU::Break();
+			// Fake a DSI so that all the code that tests for it in order to skip
+			// the rest of the instruction will apply.  (This means that
+			// watchpoints will stop the emulator before the offending load/store,
+			// not after like GDB does, but that's better anyway.  Just need to
+			// make sure resuming after that works.)
+			// It doesn't matter if ReadFromHardware triggers its own DSI because
+			// we'll take it after resuming.
+			PowerPC::ppcState.Exceptions |= EXCEPTION_DSI | EXCEPTION_FAKE_MEMCHECK_HIT;
+		}
 	}
 #endif
 }

Source/Core/Core/PowerPC/PowerPC.cpp

@@ -375,6 +375,12 @@ void CheckExceptions()
 		INFO_LOG(POWERPC, "EXCEPTION_FPU_UNAVAILABLE");
 		ppcState.Exceptions &= ~EXCEPTION_FPU_UNAVAILABLE;
 	}
+#ifdef ENABLE_MEM_CHECK
+	else if (exceptions & EXCEPTION_FAKE_MEMCHECK_HIT)
+	{
+		ppcState.Exceptions &= ~EXCEPTION_DSI & ~EXCEPTION_FAKE_MEMCHECK_HIT;
+	}
+#endif
 	else if (exceptions & EXCEPTION_DSI)
 	{
 		SRR0 = PC;