Add some infrastructure to be used for frameskipping

Core/HLE/sceDisplay.cpp

@@ -86,6 +86,7 @@ static int hCount;
 static int hCountTotal; //unused
 static int vCount;
 static int isVblank;
+static int numSkippedFrames;
 static bool hasSetMode;
 // Don't include this in the state, time increases regardless of state.
 static double lastFrameTime;
@@ -113,6 +114,7 @@ void hleAfterFlip(u64 userdata, int cyclesLate);
 void __DisplayInit() {
 	gpuStats.reset();
 	hasSetMode = false;
+	numSkippedFrames = 0;
 	framebufIsLatched = false;
 	framebuf.topaddr = 0x04000000;
 	framebuf.pspFramebufFormat = PSP_DISPLAY_PIXEL_FORMAT_8888;
@@ -264,12 +266,15 @@ void DebugStats()
 }
 
 // Let's collect all the throttling and frameskipping logic here.
-void DoFrameTiming(bool &throttle) {
+void DoFrameTiming(bool &throttle, bool &skipFrame, bool &skipFlip) {
 #ifdef _WIN32
 	throttle = !GetAsyncKeyState(VK_TAB);
 #else
 	throttle = false;
 #endif
+	skipFlip = false;
+	skipFrame = false;
+
 	if (PSP_CoreParameter().headLess)
 		throttle = false;
 
@@ -353,17 +358,27 @@ void hleEnterVblank(u64 userdata, int cyclesLate) {
 	// Yeah, this has to be the right moment to end the frame. Give the graphics backend opportunity
 	// to blit the framebuffer, in order to support half-framerate games that otherwise wouldn't have
 	// anything to draw here.
-	gpu->CopyDisplayToOutput();
+	gstate_c.skipDrawReason &= ~SKIPDRAW_SKIPFRAME;
 
-	bool throttle;
+	bool throttle, skipFrame, skipFlip;
 	
-	DoFrameTiming(throttle);
+	DoFrameTiming(throttle, skipFrame, skipFlip);
 
 	// Setting CORE_NEXTFRAME causes a swap.
-	coreState = CORE_NEXTFRAME;
+	if (skipFrame) {
+		gstate_c.skipDrawReason |= SKIPDRAW_SKIPFRAME;
+		numSkippedFrames++;
+	}	else {
+		numSkippedFrames = 0;
+	}
 
+	if (!skipFlip) {
+		coreState = CORE_NEXTFRAME;
 		CoreTiming::ScheduleEvent(0 - cyclesLate, afterFlipEvent, 0);
 
+		gpu->CopyDisplayToOutput();
+	}
+
 	// Returning here with coreState == CORE_NEXTFRAME causes a buffer flip to happen (next frame).
 	// Right after, we regain control for a little bit in hleAfterFlip. I think that's a great
 	// place to do housekeeping.

GPU/GLES/DisplayListInterpreter.cpp

@@ -330,6 +330,9 @@ void GLES_GPU::ExecuteOp(u32 op, u32 diff) {
 
 	case GE_CMD_PRIM:
 		{
+			if (gstate_c.skipDrawReason)
+				return;
+
 			framebufferManager_.SetRenderFrameBuffer();
 
 			u32 count = data & 0xFFFF;

GPU/GLES/DisplayListInterpreter.h

@@ -64,7 +64,6 @@ public:
 		return textureCache_.DecodeTexture(dest, state);
 	}
 
-
 	std::vector<FramebufferInfo> GetFramebufferList();
 
 private:

GPU/GPUState.h

@@ -225,6 +225,10 @@ struct GPUgstate
 // Real data in the context ends here
 };
 
+enum SkipDrawReasonFlags {
+	SKIPDRAW_SKIPFRAME = 1,
+};
+
 // The rest is cached simplified/converted data for fast access.
 // Does not need to be saved when saving/restoring context.
 struct GPUStateCache
@@ -236,6 +240,8 @@ struct GPUStateCache
 
 	bool textureChanged;
 
+	int skipDrawReason;
+
 	float uScale,vScale;
 	float uOff,vOff;
 	bool flipTexture;