From d8bc2050bef1c9b313a7cec13b14b8504fe9a6f9 Mon Sep 17 00:00:00 2001
From: byuu <2107894+byuu@users.noreply.github.com>
Date: Wed, 9 Oct 2019 00:45:57 +0900
Subject: [PATCH] v111.4

Serialization improvements.
---
 bsnes/emulator/emulator.hpp                   |  2 +-
 bsnes/sfc/coprocessor/armdsp/armdsp.cpp       |  5 +-
 bsnes/sfc/coprocessor/epsonrtc/epsonrtc.cpp   |  5 +-
 bsnes/sfc/coprocessor/event/event.cpp         |  5 +-
 .../sfc/coprocessor/hitachidsp/hitachidsp.cpp |  5 +-
 bsnes/sfc/coprocessor/icd/icd.cpp             |  8 ++-
 bsnes/sfc/coprocessor/msu1/msu1.cpp           |  5 +-
 bsnes/sfc/coprocessor/necdsp/necdsp.cpp       |  5 +-
 bsnes/sfc/coprocessor/sa1/sa1.cpp             |  8 ++-
 bsnes/sfc/coprocessor/sa1/sa1.hpp             |  2 +-
 bsnes/sfc/coprocessor/sharprtc/sharprtc.cpp   |  5 +-
 bsnes/sfc/coprocessor/spc7110/spc7110.cpp     |  5 +-
 bsnes/sfc/coprocessor/superfx/superfx.cpp     |  5 +-
 bsnes/sfc/coprocessor/superfx/superfx.hpp     |  2 +-
 bsnes/sfc/cpu/cpu.cpp                         | 12 ++--
 bsnes/sfc/cpu/cpu.hpp                         |  2 +-
 bsnes/sfc/ppu-fast/ppu.cpp                    |  5 +-
 bsnes/sfc/ppu/ppu.cpp                         |  5 +-
 bsnes/sfc/sfc.hpp                             | 29 ++++++----
 bsnes/sfc/slot/bsmemory/bsmemory.cpp          |  5 +-
 bsnes/sfc/smp/smp.cpp                         |  8 ++-
 bsnes/sfc/smp/smp.hpp                         |  2 +-
 bsnes/sfc/system/system.cpp                   | 55 ++++++++++---------
 bsnes/sfc/system/system.hpp                   |  3 +-
 libco/amd64.c                                 | 15 +++++
 libco/libco.h                                 |  3 +
 26 files changed, 115 insertions(+), 96 deletions(-)

diff --git a/bsnes/emulator/emulator.hpp b/bsnes/emulator/emulator.hpp
index aa60c8b8..607b0fa7 100644
--- a/bsnes/emulator/emulator.hpp
+++ b/bsnes/emulator/emulator.hpp
@@ -29,7 +29,7 @@ using namespace nall;
 
 namespace Emulator {
   static const string Name    = "bsnes";
-  static const string Version = "111.3";
+  static const string Version = "111.4";
   static const string Author  = "byuu";
   static const string License = "GPLv3";
   static const string Website = "https://byuu.org";
diff --git a/bsnes/sfc/coprocessor/armdsp/armdsp.cpp b/bsnes/sfc/coprocessor/armdsp/armdsp.cpp
index 29095b11..8a7d08d0 100644
--- a/bsnes/sfc/coprocessor/armdsp/armdsp.cpp
+++ b/bsnes/sfc/coprocessor/armdsp/armdsp.cpp
@@ -7,14 +7,13 @@ namespace SuperFamicom {
 ArmDSP armdsp;
 
 auto ArmDSP::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto ArmDSP::Enter() -> void {
   armdsp.boot();
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     armdsp.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/epsonrtc/epsonrtc.cpp b/bsnes/sfc/coprocessor/epsonrtc/epsonrtc.cpp
index de700ce9..74e0c2fe 100644
--- a/bsnes/sfc/coprocessor/epsonrtc/epsonrtc.cpp
+++ b/bsnes/sfc/coprocessor/epsonrtc/epsonrtc.cpp
@@ -8,13 +8,12 @@ namespace SuperFamicom {
 EpsonRTC epsonrtc;
 
 auto EpsonRTC::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto EpsonRTC::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     epsonrtc.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/event/event.cpp b/bsnes/sfc/coprocessor/event/event.cpp
index 2316c3e2..08c053a3 100644
--- a/bsnes/sfc/coprocessor/event/event.cpp
+++ b/bsnes/sfc/coprocessor/event/event.cpp
@@ -6,13 +6,12 @@ namespace SuperFamicom {
 Event event;
 
 auto Event::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto Event::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     event.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/hitachidsp/hitachidsp.cpp b/bsnes/sfc/coprocessor/hitachidsp/hitachidsp.cpp
index 5b07b634..c4d2a513 100644
--- a/bsnes/sfc/coprocessor/hitachidsp/hitachidsp.cpp
+++ b/bsnes/sfc/coprocessor/hitachidsp/hitachidsp.cpp
@@ -9,13 +9,12 @@ namespace SuperFamicom {
 HitachiDSP hitachidsp;
 
 auto HitachiDSP::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto HitachiDSP::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     hitachidsp.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/icd/icd.cpp b/bsnes/sfc/coprocessor/icd/icd.cpp
index 788cd8a5..d5a7f12d 100644
--- a/bsnes/sfc/coprocessor/icd/icd.cpp
+++ b/bsnes/sfc/coprocessor/icd/icd.cpp
@@ -48,13 +48,15 @@ namespace SameBoy {
 }
 
 auto ICD::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) {
+    scheduler.desynchronize();
+    co_switch(cpu.thread);
+  }
 }
 
 auto ICD::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     icd.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/msu1/msu1.cpp b/bsnes/sfc/coprocessor/msu1/msu1.cpp
index b0b891bb..046e7101 100644
--- a/bsnes/sfc/coprocessor/msu1/msu1.cpp
+++ b/bsnes/sfc/coprocessor/msu1/msu1.cpp
@@ -7,14 +7,13 @@ MSU1 msu1;
 #include "serialization.cpp"
 
 auto MSU1::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 
 auto MSU1::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     msu1.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/necdsp/necdsp.cpp b/bsnes/sfc/coprocessor/necdsp/necdsp.cpp
index fbbdb3d6..3942d98a 100644
--- a/bsnes/sfc/coprocessor/necdsp/necdsp.cpp
+++ b/bsnes/sfc/coprocessor/necdsp/necdsp.cpp
@@ -7,13 +7,12 @@ namespace SuperFamicom {
 NECDSP necdsp;
 
 auto NECDSP::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto NECDSP::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     necdsp.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/sa1/sa1.cpp b/bsnes/sfc/coprocessor/sa1/sa1.cpp
index 0a87173c..5e487f7a 100644
--- a/bsnes/sfc/coprocessor/sa1/sa1.cpp
+++ b/bsnes/sfc/coprocessor/sa1/sa1.cpp
@@ -12,13 +12,15 @@ namespace SuperFamicom {
 SA1 sa1;
 
 auto SA1::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) {
+    scheduler.desynchronize();
+    co_switch(cpu.thread);
+  }
 }
 
 auto SA1::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     sa1.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/sa1/sa1.hpp b/bsnes/sfc/coprocessor/sa1/sa1.hpp
index 21c46656..66dc6c4c 100644
--- a/bsnes/sfc/coprocessor/sa1/sa1.hpp
+++ b/bsnes/sfc/coprocessor/sa1/sa1.hpp
@@ -1,7 +1,7 @@
 //Super Accelerator (SA-1)
 
 struct SA1 : Processor::WDC65816, Thread {
-  inline auto synchronizing() const -> bool override { return scheduler.synchronizingAll(); }
+  inline auto synchronizing() const -> bool override { return scheduler.synchronizing(); }
 
   //sa1.cpp
   auto synchronizeCPU() -> void;
diff --git a/bsnes/sfc/coprocessor/sharprtc/sharprtc.cpp b/bsnes/sfc/coprocessor/sharprtc/sharprtc.cpp
index 372ffd56..70782657 100644
--- a/bsnes/sfc/coprocessor/sharprtc/sharprtc.cpp
+++ b/bsnes/sfc/coprocessor/sharprtc/sharprtc.cpp
@@ -8,13 +8,12 @@ namespace SuperFamicom {
 SharpRTC sharprtc;
 
 auto SharpRTC::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto SharpRTC::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     sharprtc.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/spc7110/spc7110.cpp b/bsnes/sfc/coprocessor/spc7110/spc7110.cpp
index 85c7354c..a2981245 100644
--- a/bsnes/sfc/coprocessor/spc7110/spc7110.cpp
+++ b/bsnes/sfc/coprocessor/spc7110/spc7110.cpp
@@ -17,13 +17,12 @@ SPC7110::~SPC7110() {
 }
 
 auto SPC7110::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto SPC7110::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     spc7110.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/superfx/superfx.cpp b/bsnes/sfc/coprocessor/superfx/superfx.cpp
index b9ddf09d..847f6a06 100644
--- a/bsnes/sfc/coprocessor/superfx/superfx.cpp
+++ b/bsnes/sfc/coprocessor/superfx/superfx.cpp
@@ -12,13 +12,12 @@ namespace SuperFamicom {
 SuperFX superfx;
 
 auto SuperFX::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto SuperFX::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     superfx.main();
   }
 }
diff --git a/bsnes/sfc/coprocessor/superfx/superfx.hpp b/bsnes/sfc/coprocessor/superfx/superfx.hpp
index 680e9b1e..97df3dfc 100644
--- a/bsnes/sfc/coprocessor/superfx/superfx.hpp
+++ b/bsnes/sfc/coprocessor/superfx/superfx.hpp
@@ -2,7 +2,7 @@ struct SuperFX : Processor::GSU, Thread {
   ReadableMemory rom;
   WritableMemory ram;
 
-  inline auto synchronizing() const -> bool { return scheduler.synchronizingAll(); }
+  inline auto synchronizing() const -> bool { return scheduler.synchronizing(); }
 
   //superfx.cpp
   auto synchronizeCPU() -> void;
diff --git a/bsnes/sfc/cpu/cpu.cpp b/bsnes/sfc/cpu/cpu.cpp
index 2505dc92..45566eb1 100644
--- a/bsnes/sfc/cpu/cpu.cpp
+++ b/bsnes/sfc/cpu/cpu.cpp
@@ -11,26 +11,22 @@ CPU cpu;
 #include "serialization.cpp"
 
 auto CPU::synchronizeSMP() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(smp.clock < 0) co_switch(smp.thread);
+  if(smp.clock < 0) scheduler.resume(smp.thread);
 }
 
 auto CPU::synchronizePPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(ppu.clock < 0) co_switch(ppu.thread);
+  if(ppu.clock < 0) scheduler.resume(ppu.thread);
 }
 
 auto CPU::synchronizeCoprocessors() -> void {
-  if(scheduler.synchronizingAll()) return;
   for(auto coprocessor : coprocessors) {
-    if(coprocessor->clock < 0) co_switch(coprocessor->thread);
+    if(coprocessor->clock < 0) scheduler.resume(coprocessor->thread);
   }
 }
 
 auto CPU::Enter() -> void {
   while(true) {
-    scheduler.synchronizeCPU();
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     cpu.main();
   }
 }
diff --git a/bsnes/sfc/cpu/cpu.hpp b/bsnes/sfc/cpu/cpu.hpp
index bac32b3e..154270c6 100644
--- a/bsnes/sfc/cpu/cpu.hpp
+++ b/bsnes/sfc/cpu/cpu.hpp
@@ -2,7 +2,7 @@ struct CPU : Processor::WDC65816, Thread, PPUcounter {
   inline auto interruptPending() const -> bool override { return status.interruptPending; }
   inline auto pio() const -> uint8 { return io.pio; }
   inline auto refresh() const -> bool { return status.dramRefresh == 1; }
-  inline auto synchronizing() const -> bool override { return scheduler.mode == Scheduler::Mode::SynchronizeCPU; }
+  inline auto synchronizing() const -> bool override { return scheduler.synchronizing(); }
 
   //cpu.cpp
   auto synchronizeSMP() -> void;
diff --git a/bsnes/sfc/ppu-fast/ppu.cpp b/bsnes/sfc/ppu-fast/ppu.cpp
index 6dd09b6c..0d1d8eb4 100644
--- a/bsnes/sfc/ppu-fast/ppu.cpp
+++ b/bsnes/sfc/ppu-fast/ppu.cpp
@@ -69,13 +69,12 @@ PPU::~PPU() {
 }
 
 auto PPU::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(ppubase.clock >= 0) co_switch(cpu.thread);
+  if(ppubase.clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto PPU::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     ppu.main();
   }
 }
diff --git a/bsnes/sfc/ppu/ppu.cpp b/bsnes/sfc/ppu/ppu.cpp
index a3de2dca..f5ede96d 100644
--- a/bsnes/sfc/ppu/ppu.cpp
+++ b/bsnes/sfc/ppu/ppu.cpp
@@ -39,8 +39,7 @@ PPU::~PPU() {
 }
 
 auto PPU::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto PPU::step() -> void {
@@ -60,7 +59,7 @@ auto PPU::step(uint clocks) -> void {
 
 auto PPU::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     ppu.main();
   }
 }
diff --git a/bsnes/sfc/sfc.hpp b/bsnes/sfc/sfc.hpp
index 0f209dcf..7171b29b 100644
--- a/bsnes/sfc/sfc.hpp
+++ b/bsnes/sfc/sfc.hpp
@@ -28,11 +28,12 @@ namespace SuperFamicom {
   extern Cheat cheat;
 
   struct Scheduler {
-    enum class Mode : uint { Run, SynchronizeCPU, SynchronizeAll } mode;
-    enum class Event : uint { Frame, Synchronize } event;
+    enum class Mode : uint { Run, Synchronize } mode;
+    enum class Event : uint { Frame, Synchronized, Desynchronized } event;
 
     cothread_t host = nullptr;
     cothread_t active = nullptr;
+    bool desynchronized = false;
 
     auto enter() -> void {
       host = co_active();
@@ -45,20 +46,28 @@ namespace SuperFamicom {
       co_switch(host);
     }
 
-    inline auto synchronizingCPU() const -> bool {
-      return mode == Mode::SynchronizeCPU;
+    auto resume(cothread_t thread) -> void {
+      if(mode == Mode::Synchronize) desynchronized = true;
+      co_switch(thread);
     }
 
-    inline auto synchronizingAll() const -> bool {
-      return mode == Mode::SynchronizeAll;
+    inline auto synchronizing() const -> bool {
+      return mode == Mode::Synchronize;
     }
 
-    inline auto synchronizeCPU() -> void {
-      if(mode == Mode::SynchronizeCPU) leave(Event::Synchronize);
+    inline auto synchronize() -> void {
+      if(mode == Mode::Synchronize) {
+        if(desynchronized) {
+          desynchronized = false;
+          leave(Event::Desynchronized);
+        } else {
+          leave(Event::Synchronized);
+        }
+      }
     }
 
-    inline auto synchronizeAll() -> void {
-      if(mode == Mode::SynchronizeAll) leave(Event::Synchronize);
+    inline auto desynchronize() -> void {
+      desynchronized = true;
     }
   };
   extern Scheduler scheduler;
diff --git a/bsnes/sfc/slot/bsmemory/bsmemory.cpp b/bsnes/sfc/slot/bsmemory/bsmemory.cpp
index 17f51a48..3adf0750 100644
--- a/bsnes/sfc/slot/bsmemory/bsmemory.cpp
+++ b/bsnes/sfc/slot/bsmemory/bsmemory.cpp
@@ -13,13 +13,12 @@ BSMemory::BSMemory() {
 }
 
 auto BSMemory::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) scheduler.resume(cpu.thread);
 }
 
 auto BSMemory::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     bsmemory.main();
   }
 }
diff --git a/bsnes/sfc/smp/smp.cpp b/bsnes/sfc/smp/smp.cpp
index 7d9ae842..9a746b9a 100644
--- a/bsnes/sfc/smp/smp.cpp
+++ b/bsnes/sfc/smp/smp.cpp
@@ -9,8 +9,10 @@ SMP smp;
 #include "serialization.cpp"
 
 auto SMP::synchronizeCPU() -> void {
-  if(scheduler.synchronizingAll()) return;
-  if(clock >= 0) co_switch(cpu.thread);
+  if(clock >= 0) {
+    scheduler.desynchronize();
+    co_switch(cpu.thread);
+  }
 }
 
 auto SMP::synchronizeDSP() -> void {
@@ -19,7 +21,7 @@ auto SMP::synchronizeDSP() -> void {
 
 auto SMP::Enter() -> void {
   while(true) {
-    scheduler.synchronizeAll();
+    scheduler.synchronize();
     smp.main();
   }
 }
diff --git a/bsnes/sfc/smp/smp.hpp b/bsnes/sfc/smp/smp.hpp
index c973c079..b23bfaae 100644
--- a/bsnes/sfc/smp/smp.hpp
+++ b/bsnes/sfc/smp/smp.hpp
@@ -1,7 +1,7 @@
 //Sony CXP1100Q-1
 
 struct SMP : Processor::SPC700, Thread {
-  inline auto synchronizing() const -> bool override { return scheduler.synchronizingAll(); }
+  inline auto synchronizing() const -> bool override { return scheduler.synchronizing(); }
 
   //io.cpp
   auto portRead(uint2 port) const -> uint8;
diff --git a/bsnes/sfc/system/system.cpp b/bsnes/sfc/system/system.cpp
index d83689cd..c2e179ee 100644
--- a/bsnes/sfc/system/system.cpp
+++ b/bsnes/sfc/system/system.cpp
@@ -15,44 +15,47 @@ auto System::run() -> void {
 }
 
 auto System::runToSave() -> void {
-  //run the CPU thread normally, exiting once we reach the next synchronization point.
-  //the CPU thread may run in the pathological case for up to 10 frames for a long 8-channel x 64KB DMA transfer.
-  //in practice, this will typically be at most one DMA transfer.
-  scheduler.mode = Scheduler::Mode::SynchronizeCPU;
-  runToSynchronize();
+  while(true) {
+    //SMP thread is synchronized twice to ensure the CPU and SMP are closely aligned:
+    //this is extremely critical for Tales of Phantasia and Star Ocean.
+    scheduler.mode = Scheduler::Mode::Synchronize;
+    scheduler.active = smp.thread;
+    if(!runToSynchronize()) continue;
 
-  //now synchronize every other thread to their synchronization points.
-  //stop after each thread is very slightly ahead of the CPU thread.
-  scheduler.mode = Scheduler::Mode::SynchronizeAll;
-  runToThread(smp);
-  runToThread(ppu);
-  for(auto coprocessor : cpu.coprocessors) runToThread(*coprocessor);
+    scheduler.mode = Scheduler::Mode::Synchronize;
+    scheduler.active = cpu.thread;
+    if(!runToSynchronize()) continue;
+
+    scheduler.mode = Scheduler::Mode::Synchronize;
+    scheduler.active = smp.thread;
+    if(!runToSynchronize()) continue;
+
+    scheduler.mode = Scheduler::Mode::Synchronize;
+    scheduler.active = ppu.thread;
+    if(!runToSynchronize()) continue;
+
+    for(auto coprocessor : cpu.coprocessors) {
+      scheduler.mode = Scheduler::Mode::Synchronize;
+      scheduler.active = coprocessor->thread;
+      if(!runToSynchronize()) continue;
+    }
+
+    break;
+  }
 
-  //at this point, the CPU thread is the furthest behind in time.
-  //all threads are now at their synchronization points and can be serialized safely.
   scheduler.mode = Scheduler::Mode::Run;
   scheduler.active = cpu.thread;
 }
 
-auto System::runToSynchronize() -> void {
+auto System::runToSynchronize() -> bool {
   while(true) {
     scheduler.enter();
     if(scheduler.event == Scheduler::Event::Frame) frameEvent();
-    if(scheduler.event == Scheduler::Event::Synchronize) break;
+    if(scheduler.event == Scheduler::Event::Synchronized) return true;
+    if(scheduler.event == Scheduler::Event::Desynchronized) return false;
   }
 }
 
-auto System::runToThread(Thread& aux) -> void {
-  //first, ensure that the CPU is ahead of the thread we want to synchronize to.
-  //because if it isn't, and the other thread is ahead, it will run even more ahead to synchronize itself.
-  scheduler.active = cpu.thread;
-  while(aux.clock >= 0) runToSynchronize();
-
-  //now that it is, run the other thread until it's just barely surpassed the CPU thread.
-  scheduler.active = aux.thread;
-  do runToSynchronize(); while(aux.clock < 0);
-}
-
 auto System::frameEvent() -> void {
   ppu.refresh();
 
diff --git a/bsnes/sfc/system/system.hpp b/bsnes/sfc/system/system.hpp
index 3e717dc7..eae0532d 100644
--- a/bsnes/sfc/system/system.hpp
+++ b/bsnes/sfc/system/system.hpp
@@ -10,8 +10,7 @@ struct System {
 
   auto run() -> void;
   auto runToSave() -> void;
-  auto runToSynchronize() -> void;
-  auto runToThread(Thread&) -> void;
+  auto runToSynchronize() -> bool;
   auto frameEvent() -> void;
 
   auto load(Emulator::Interface*) -> bool;
diff --git a/libco/amd64.c b/libco/amd64.c
index ab62bd92..686b8565 100755
--- a/libco/amd64.c
+++ b/libco/amd64.c
@@ -4,6 +4,7 @@
 
 #include <assert.h>
 #include <stdlib.h>
+#include <string.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -167,6 +168,20 @@ void co_switch(cothread_t handle) {
   co_swap(co_active_handle = handle, co_previous_handle);
 }
 
+unsigned int co_size(unsigned int size) {
+  size += 512;
+  size &= ~15;
+  return size;
+}
+
+void co_save(cothread_t handle, void* memory, unsigned int size) {
+  memcpy(memory, handle, size);
+}
+
+void co_load(cothread_t handle, const void* memory, unsigned int size) {
+  memcpy(handle, memory, size);
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libco/libco.h b/libco/libco.h
index b7f60852..0a5db70a 100755
--- a/libco/libco.h
+++ b/libco/libco.h
@@ -18,6 +18,9 @@ cothread_t co_derive(void*, unsigned int, void (*)(void));
 cothread_t co_create(unsigned int, void (*)(void));
 void co_delete(cothread_t);
 void co_switch(cothread_t);
+unsigned int co_size(unsigned int);
+void co_save(cothread_t, void*, unsigned int);
+void co_load(cothread_t, const void*, unsigned int);
 
 #ifdef __cplusplus
 }