HLE : Move IsXboxCodeAddress check into it's own function, and call it first in IsXboxCodeAddress (instead of later, in EmuX86_DecodeException).

Also, optimize IsRdtscInstruction() and it's emulation, by calling directly into CxbxRdTsc(). Additionally, use unsigned ULARGE_INTEGER and ULONGLONG variables.

src/CxbxKrnl/CxbxKrnl.cpp

@@ -689,14 +689,13 @@ bool IsRdtscInstruction(xbaddr addr)
 {
 	// First the fastest check - is this a patch? (see PatchRdtsc)
 	uint8_t* opAddr = (uint8_t*)addr;
-	if ((opAddr[0] == 0xEF) // OUT DX, EAX
-	 && (opAddr[1] == 0x90)) { // NOP
-		if (std::find(g_RdtscPatches.begin(), g_RdtscPatches.end(), addr) != g_RdtscPatches.end()) {
-			return true;
-		}
-	}
-
-	return false;
+	// Note : Check second opcode first, as that's most likely to fail fast
+	return (opAddr[1] == 0x90) // NOP
+		&& (opAddr[0] == 0xEF) // OUT DX, EAX
+		// Note : It's not needed to check for g_SkipRdtscPatching,
+		// as when that's set, the g_RdtscPatches vector will be empty
+		// anyway, failing this lookup :
+		&& (std::find(g_RdtscPatches.begin(), g_RdtscPatches.end(), addr) != g_RdtscPatches.end());
 }
 
 void PatchRdtsc(xbaddr addr)

src/CxbxKrnl/Emu.cpp

@@ -216,25 +216,41 @@ void EmuExceptionNonBreakpointUnhandledShow(LPEXCEPTION_POINTERS e)
 	}
 }
 
+// Returns weither the given address is part of an Xbox managed memory region
+bool IsXboxCodeAddress(xbaddr addr)
+{
+	// TODO : Replace the following with a (fast) check weither
+	// the given address lies in xbox allocated virtual memory,
+	// for example by g_VMManager.CheckConflictingVMA(addr, 0).
+	return (addr >= XBE_IMAGE_BASE) && (addr <= XBE_MAX_VA);
+	// Note : Not IS_USER_ADDRESS(), that would include host DLL code
+}
+
 bool IsRdtscInstruction(xbaddr addr);
+ULONGLONG CxbxRdTsc(bool xbox);
 bool TryHandleException(EXCEPTION_POINTERS *e)
 {
+	// Only handle exceptions which originate from Xbox code
+	if (!IsXboxCodeAddress(e->ContextRecord->Eip)) {
+		return false;
+	}
+
 	// Make sure access-violations reach EmuX86_DecodeException() as soon as possible
 	if (e->ExceptionRecord->ExceptionCode != EXCEPTION_ACCESS_VIOLATION) {
 		switch (e->ExceptionRecord->ExceptionCode) {
 		case STATUS_PRIVILEGED_INSTRUCTION:
-			// When the g_SkipRdtscPatching hack is disabled
-			if (!g_SkipRdtscPatching) {
-				// Check if this exception came from rdtsc 
-				if (IsRdtscInstruction(e->ContextRecord->Eip)) {
-					LARGE_INTEGER PerformanceCount;
-					PerformanceCount.QuadPart = xboxkrnl::KeQueryPerformanceCounter();
-					e->ContextRecord->Eax = PerformanceCount.LowPart;
-					e->ContextRecord->Edx = PerformanceCount.HighPart;
-					e->ContextRecord->Eip += 2;
-					return true;
-				}
-			}
+			// Check if this exception came from rdtsc 
+			if (IsRdtscInstruction(e->ContextRecord->Eip)) {
+				// If so, use a return value that updates with Xbox frequency;
+				// Avoid the overhead of xboxkrnl::KeQueryPerformanceCounter,
+				// by calling directly into it's backing implementation:
+				ULARGE_INTEGER PerformanceCount;
+				PerformanceCount.QuadPart = CxbxRdTsc(/*xbox=*/true);
+				e->ContextRecord->Eax = PerformanceCount.LowPart;
+				e->ContextRecord->Edx = PerformanceCount.HighPart;
+				e->ContextRecord->Eip += 2;
+				return true;
+			}
 			break;
 		case STATUS_BREAKPOINT:
 			// Let user choose between continue or break

src/CxbxKrnl/EmuKrnlKe.cpp

@@ -248,21 +248,21 @@ void InitDpcAndTimerThread()
 
 // Xbox Performance Counter Frequency = 733333333 (CPU Clock)
 #define XBOX_PERFORMANCE_FREQUENCY 733333333
-uint64_t NativeToXbox_FactorForPerformanceFrequency;
+ULONGLONG NativeToXbox_FactorForPerformanceFrequency;
 
 void ConnectKeInterruptTimeToThunkTable(); // forward
 
-uint64_t CxbxRdTsc(bool xbox) {
+ULONGLONG CxbxRdTsc(bool xbox) {
 	LARGE_INTEGER tsc;
 
 	QueryPerformanceCounter(&tsc);
 
 	if (xbox && NativeToXbox_FactorForPerformanceFrequency) {
-		LARGE_INTEGER scaledTsc;
+		ULARGE_INTEGER scaledTsc;
 		scaledTsc.QuadPart = 1000000000;
-		scaledTsc.QuadPart *= tsc.QuadPart;
+		scaledTsc.QuadPart *= (ULONGLONG)tsc.QuadPart;
 		scaledTsc.QuadPart /= NativeToXbox_FactorForPerformanceFrequency;
-		return (uint64_t)scaledTsc.QuadPart;
+		return scaledTsc.QuadPart;
 	}
 
 	return (uint64_t)tsc.QuadPart;
@@ -1127,8 +1127,8 @@ XBSYSAPI EXPORTNUM(126) xboxkrnl::ULONGLONG NTAPI xboxkrnl::KeQueryPerformanceCo
 	ULONGLONG ret;
 
 	//no matter rdtsc is patched or not, we should always return a scaled performance counter here.
-	DbgPrintf("host tick count       : %lu\n", CxbxRdTsc(false));
-	ret = CxbxRdTsc(true);
+	DbgPrintf("host tick count       : %lu\n", CxbxRdTsc(/*xbox=*/false));
+	ret = CxbxRdTsc(/*xbox=*/true);
 	DbgPrintf("emulated tick count   : %lu\n", ret);
 	
 	RETURN(ret);

src/CxbxKrnl/EmuX86.cpp

@@ -1043,11 +1043,6 @@ int EmuX86_OpcodeSize(uint8_t *Eip)
 
 bool EmuX86_DecodeException(LPEXCEPTION_POINTERS e)
 {
-	// Only decode instructions which reside in the loaded Xbe
-	if (e->ContextRecord->Eip > XBE_MAX_VA || e->ContextRecord->Eip < XBE_IMAGE_BASE) {
-		return false;
-	}
-
 	// Decoded instruction information.
 	// Opcode handler note : 
 	// If an opcode or one of it's operand can't be decoded, that's a clear failure.
@@ -1137,7 +1132,7 @@ void EmuX86_Init()
 {
 	DbgPrintf("X86 : Initializing distorm version %d\n", distorm_version());
 #ifndef USE_SEH // implies VEH
-	AddVectoredExceptionHandler(1, EmuException);
+	AddVectoredExceptionHandler(/*FirstHandler=*/ULONG(true), EmuException);
 #endif // !USE_SEG
 	EmuX86_InitContextRecordOffsetByRegisterType();
 }