snes: ppu: state out similarly to apu. this was a very simple project; unlike the apu, there aren't many sync points. like the apu, a message is dumped to the console if runtosave causes determinism problems. like the apu, there's no speed hit, but tales of phantasia is still broken. breaks savesates.

libsnes/bsnes/snes/alt/ppu-compatibility/ppu.cpp

@@ -16,7 +16,10 @@ void PPU::step(unsigned clocks) {
 
 void PPU::synchronize_cpu() {
   if(CPU::Threaded == true) {
-    if(clock >= 0 && scheduler.sync != Scheduler::SynchronizeMode::All) co_switch(cpu.thread);
+    if(clock >= 0 && scheduler.sync != Scheduler::SynchronizeMode::All)
+      co_switch(cpu.thread);
+    else if(clock >= 0 && scheduler.sync == Scheduler::SynchronizeMode::All)
+      interface->message("PPU had to advance nondeterministically!");
   } else {
     while(clock >= 0) cpu.enter();
   }
@@ -28,12 +31,27 @@ void PPU::enter() {
   while(true) {
     if(scheduler.sync == Scheduler::SynchronizeMode::All) {
       scheduler.exit(Scheduler::ExitReason::SynchronizeEvent);
-    }
-
+    }
+
+    switch(uindex)
+    {
+      case 0: enter1(); break;
+      case 1: enter2(); break;
+      case 2: enter3(); break;
+      case 3: enter4(); break;
+    }
+    uindex++;
+    uindex &= 3;
+  }
+}
+
+void PPU::enter1() {
     //H =    0 (initialize)
     scanline();
     add_clocks(10);
-
+}
+
+void PPU::enter2() {
     //H =   10 (cache mode7 registers + OAM address reset)
     cache.m7_hofs = regs.m7_hofs;
     cache.m7_vofs = regs.m7_vofs;
@@ -50,11 +68,15 @@ void PPU::enter() {
       }
     }
     add_clocks(502);
-
+}
+
+void PPU::enter3() {
     //H =  512 (render)
     render_scanline();
     add_clocks(640);
-
+}
+
+void PPU::enter4() {
     //H = 1152 (cache OBSEL)
     if(cache.oam_basesize != regs.oam_basesize) {
       cache.oam_basesize = regs.oam_basesize;
@@ -63,8 +85,6 @@ void PPU::enter() {
     cache.oam_nameselect = regs.oam_nameselect;
     cache.oam_tdaddr = regs.oam_tdaddr;
     add_clocks(lineclocks() - 1152);  //seek to start of next scanline
-
-  }
 }
 
 void PPU::add_clocks(unsigned clocks) {
@@ -349,6 +369,8 @@ void PPU::reset() {
   create(Enter, system.cpu_frequency());
   PPUcounter::reset();
   memset(surface, 0, 512 * 512 * sizeof(uint32));
+
+  uindex = 0;
 
 	//zero 01-dec-2012 - gotta reset these sometime, somewhere
 	memset(oam_itemlist, 0, sizeof(oam_itemlist));

libsnes/bsnes/snes/alt/ppu-compatibility/ppu.hpp

@@ -11,6 +11,8 @@ public:
   #include "memory/memory.hpp"
   #include "mmio/mmio.hpp"
   #include "render/render.hpp"
+
+  int uindex;
 
   uint32 *surface;
   uint32 *output;
@@ -58,7 +60,11 @@ public:
   void scanline();
   void render_scanline();
   void frame();
-  void enter();
+  void enter();
+  void enter1();
+  void enter2();
+  void enter3();
+  void enter4();
   void enable();
   void power();
   void reset();

libsnes/bsnes/snes/alt/ppu-compatibility/serialization.cpp

@@ -201,7 +201,9 @@ void PPU::serialize(serializer &s) {
   }
 
   s.array(oam_line_pal, 256);
-  s.array(oam_line_pri, 256);
+  s.array(oam_line_pri, 256);
+
+  s.integer(uindex);
 }
 
 #endif