dolphin/Source/Core/VideoCommon/Fifo.cpp

// Copyright 2008 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#include <atomic>
#include <cstring>

#include "Common/Assert.h"
#include "Common/Atomic.h"
#include "Common/BlockingLoop.h"
#include "Common/ChunkFile.h"
#include "Common/Event.h"
#include "Common/FPURoundMode.h"
#include "Common/MemoryUtil.h"
#include "Common/MsgHandler.h"

#include "Core/ConfigManager.h"
#include "Core/CoreTiming.h"
#include "Core/HW/Memmap.h"
#include "Core/NetPlayProto.h"

#include "VideoCommon/AsyncRequests.h"
#include "VideoCommon/CPMemory.h"
#include "VideoCommon/CommandProcessor.h"
#include "VideoCommon/DataReader.h"
#include "VideoCommon/Fifo.h"
#include "VideoCommon/OpcodeDecoding.h"
#include "VideoCommon/VertexLoaderManager.h"
#include "VideoCommon/VertexManagerBase.h"

namespace Fifo
{
static constexpr u32 FIFO_SIZE = 2 * 1024 * 1024;

static bool s_skip_current_frame = false;

static Common::BlockingLoop s_gpu_mainloop;

static Common::Flag s_emu_running_state;

// Most of this array is unlikely to be faulted in...
static u8 s_fifo_aux_data[FIFO_SIZE];
static u8* s_fifo_aux_write_ptr;
static u8* s_fifo_aux_read_ptr;

// This could be in SConfig, but it depends on multiple settings
// and can change at runtime.
static bool s_use_deterministic_gpu_thread;

static u64 s_last_sync_gpu_tick;
static int s_event_sync_gpu;

// STATE_TO_SAVE
static u8* s_video_buffer;
static u8* s_video_buffer_read_ptr;
static std::atomic<u8*> s_video_buffer_write_ptr;
static std::atomic<u8*> s_video_buffer_seen_ptr;
static u8* s_video_buffer_pp_read_ptr;
// The read_ptr is always owned by the GPU thread.  In normal mode, so is the
// write_ptr, despite it being atomic.  In deterministic GPU thread mode,
// things get a bit more complicated:
// - The seen_ptr is written by the GPU thread, and points to what it's already
// processed as much of as possible - in the case of a partial command which
// caused it to stop, not the same as the read ptr.  It's written by the GPU,
// under the lock, and updating the cond.
// - The write_ptr is written by the CPU thread after it copies data from the
// FIFO.  Maybe someday it will be under the lock.  For now, because RunGpuLoop
// polls, it's just atomic.
// - The pp_read_ptr is the CPU preprocessing version of the read_ptr.

static std::atomic<int> s_sync_ticks;
static Common::Event s_sync_wakeup_event;

void DoState(PointerWrap& p)
{
  p.DoArray(s_video_buffer, FIFO_SIZE);
  u8* write_ptr = s_video_buffer_write_ptr;
  p.DoPointer(write_ptr, s_video_buffer);
  s_video_buffer_write_ptr = write_ptr;
  p.DoPointer(s_video_buffer_read_ptr, s_video_buffer);
  if (p.mode == PointerWrap::MODE_READ && s_use_deterministic_gpu_thread)
  {
    // We're good and paused, right?
    s_video_buffer_seen_ptr = s_video_buffer_pp_read_ptr = s_video_buffer_read_ptr;
  }

  p.Do(s_skip_current_frame);
  p.Do(s_last_sync_gpu_tick);
}

void PauseAndLock(bool doLock, bool unpauseOnUnlock)
{
  if (doLock)
  {
    SyncGPU(SYNC_GPU_OTHER);
    EmulatorState(false);
    FlushGpu();
  }
  else
  {
    if (unpauseOnUnlock)
      EmulatorState(true);
  }
}

void Init()
{
  // Padded so that SIMD overreads in the vertex loader are safe
  s_video_buffer = (u8*)AllocateMemoryPages(FIFO_SIZE + 4);
  ResetVideoBuffer();
  if (SConfig::GetInstance().bCPUThread)
    s_gpu_mainloop.Prepare();
  s_sync_ticks.store(0);
}

void Shutdown()
{
  if (s_gpu_mainloop.IsRunning())
    PanicAlert("Fifo shutting down while active");

  FreeMemoryPages(s_video_buffer, FIFO_SIZE + 4);
  s_video_buffer = nullptr;
  s_video_buffer_write_ptr = nullptr;
  s_video_buffer_pp_read_ptr = nullptr;
  s_video_buffer_read_ptr = nullptr;
  s_video_buffer_seen_ptr = nullptr;
  s_fifo_aux_write_ptr = nullptr;
  s_fifo_aux_read_ptr = nullptr;
}

void SetRendering(bool enabled)
{
  s_skip_current_frame = !enabled;
}

bool WillSkipCurrentFrame()
{
  return s_skip_current_frame;
}

// May be executed from any thread, even the graphics thread.
// Created to allow for self shutdown.
void ExitGpuLoop()
{
  // This should break the wait loop in CPU thread
  CommandProcessor::fifo.bFF_GPReadEnable = false;
  FlushGpu();

  // Terminate GPU thread loop
  s_emu_running_state.Set();
  s_gpu_mainloop.Stop(false);
}

void EmulatorState(bool running)
{
  s_emu_running_state.Set(running);
  if (running)
    s_gpu_mainloop.Wakeup();
  else
    s_gpu_mainloop.AllowSleep();
}

void SyncGPU(SyncGPUReason reason, bool may_move_read_ptr)
{
  if (s_use_deterministic_gpu_thread)
  {
    s_gpu_mainloop.Wait();
    if (!s_gpu_mainloop.IsRunning())
      return;

    // Opportunistically reset FIFOs so we don't wrap around.
    if (may_move_read_ptr && s_fifo_aux_write_ptr != s_fifo_aux_read_ptr)
      PanicAlert("aux fifo not synced (%p, %p)", s_fifo_aux_write_ptr, s_fifo_aux_read_ptr);

    memmove(s_fifo_aux_data, s_fifo_aux_read_ptr, s_fifo_aux_write_ptr - s_fifo_aux_read_ptr);
    s_fifo_aux_write_ptr -= (s_fifo_aux_read_ptr - s_fifo_aux_data);
    s_fifo_aux_read_ptr = s_fifo_aux_data;

    if (may_move_read_ptr)
    {
      u8* write_ptr = s_video_buffer_write_ptr;

      // what's left over in the buffer
      size_t size = write_ptr - s_video_buffer_pp_read_ptr;

      memmove(s_video_buffer, s_video_buffer_pp_read_ptr, size);
      // This change always decreases the pointers.  We write seen_ptr
      // after write_ptr here, and read it before in RunGpuLoop, so
      // 'write_ptr > seen_ptr' there cannot become spuriously true.
      s_video_buffer_write_ptr = write_ptr = s_video_buffer + size;
      s_video_buffer_pp_read_ptr = s_video_buffer;
      s_video_buffer_read_ptr = s_video_buffer;
      s_video_buffer_seen_ptr = write_ptr;
    }
  }
}

void PushFifoAuxBuffer(void* ptr, size_t size)
{
  if (size > (size_t)(s_fifo_aux_data + FIFO_SIZE - s_fifo_aux_write_ptr))
  {
    SyncGPU(SYNC_GPU_AUX_SPACE, /* may_move_read_ptr */ false);
    if (!s_gpu_mainloop.IsRunning())
    {
      // GPU is shutting down
      return;
    }
    if (size > (size_t)(s_fifo_aux_data + FIFO_SIZE - s_fifo_aux_write_ptr))
    {
      // That will sync us up to the last 32 bytes, so this short region
      // of FIFO would have to point to a 2MB display list or something.
      PanicAlert("absurdly large aux buffer");
      return;
    }
  }
  memcpy(s_fifo_aux_write_ptr, ptr, size);
  s_fifo_aux_write_ptr += size;
}

void* PopFifoAuxBuffer(size_t size)
{
  void* ret = s_fifo_aux_read_ptr;
  s_fifo_aux_read_ptr += size;
  return ret;
}

// Description: RunGpuLoop() sends data through this function.
static void ReadDataFromFifo(u32 readPtr)
{
  size_t len = 32;
  if (len > (size_t)(s_video_buffer + FIFO_SIZE - s_video_buffer_write_ptr))
  {
    size_t existing_len = s_video_buffer_write_ptr - s_video_buffer_read_ptr;
    if (len > (size_t)(FIFO_SIZE - existing_len))
    {
      PanicAlert("FIFO out of bounds (existing %zu + new %zu > %lu)", existing_len, len,
                 (unsigned long)FIFO_SIZE);
      return;
    }
    memmove(s_video_buffer, s_video_buffer_read_ptr, existing_len);
    s_video_buffer_write_ptr = s_video_buffer + existing_len;
    s_video_buffer_read_ptr = s_video_buffer;
  }
  // Copy new video instructions to s_video_buffer for future use in rendering the new picture
  Memory::CopyFromEmu(s_video_buffer_write_ptr, readPtr, len);
  s_video_buffer_write_ptr += len;
}

// The deterministic_gpu_thread version.
static void ReadDataFromFifoOnCPU(u32 readPtr)
{
  size_t len = 32;
  u8* write_ptr = s_video_buffer_write_ptr;
  if (len > (size_t)(s_video_buffer + FIFO_SIZE - write_ptr))
  {
    // We can't wrap around while the GPU is working on the data.
    // This should be very rare due to the reset in SyncGPU.
    SyncGPU(SYNC_GPU_WRAPAROUND);
    if (!s_gpu_mainloop.IsRunning())
    {
      // GPU is shutting down, so the next asserts may fail
      return;
    }

    if (s_video_buffer_pp_read_ptr != s_video_buffer_read_ptr)
    {
      PanicAlert("desynced read pointers");
      return;
    }
    write_ptr = s_video_buffer_write_ptr;
    size_t existing_len = write_ptr - s_video_buffer_pp_read_ptr;
    if (len > (size_t)(FIFO_SIZE - existing_len))
    {
      PanicAlert("FIFO out of bounds (existing %zu + new %zu > %lu)", existing_len, len,
                 (unsigned long)FIFO_SIZE);
      return;
    }
  }
  Memory::CopyFromEmu(s_video_buffer_write_ptr, readPtr, len);
  s_video_buffer_pp_read_ptr = OpcodeDecoder::Run<true>(
      DataReader(s_video_buffer_pp_read_ptr, write_ptr + len), nullptr, false);
  // This would have to be locked if the GPU thread didn't spin.
  s_video_buffer_write_ptr = write_ptr + len;
}

void ResetVideoBuffer()
{
  s_video_buffer_read_ptr = s_video_buffer;
  s_video_buffer_write_ptr = s_video_buffer;
  s_video_buffer_seen_ptr = s_video_buffer;
  s_video_buffer_pp_read_ptr = s_video_buffer;
  s_fifo_aux_write_ptr = s_fifo_aux_data;
  s_fifo_aux_read_ptr = s_fifo_aux_data;
}

// Description: Main FIFO update loop
// Purpose: Keep the Core HW updated about the CPU-GPU distance
void RunGpuLoop()
{
  AsyncRequests::GetInstance()->SetEnable(true);
  AsyncRequests::GetInstance()->SetPassthrough(false);

  s_gpu_mainloop.Run(
      [] {
        const SConfig& param = SConfig::GetInstance();

        g_video_backend->PeekMessages();

        // Do nothing while paused
        if (!s_emu_running_state.IsSet())
          return;

        if (s_use_deterministic_gpu_thread)
        {
          AsyncRequests::GetInstance()->PullEvents();

          // All the fifo/CP stuff is on the CPU.  We just need to run the opcode decoder.
          u8* seen_ptr = s_video_buffer_seen_ptr;
          u8* write_ptr = s_video_buffer_write_ptr;
          // See comment in SyncGPU
          if (write_ptr > seen_ptr)
          {
            s_video_buffer_read_ptr =
                OpcodeDecoder::Run(DataReader(s_video_buffer_read_ptr, write_ptr), nullptr, false);
            s_video_buffer_seen_ptr = write_ptr;
          }
        }
        else
        {
          SCPFifoStruct& fifo = CommandProcessor::fifo;

          AsyncRequests::GetInstance()->PullEvents();

          CommandProcessor::SetCPStatusFromGPU();

          // check if we are able to run this buffer
          while (!CommandProcessor::IsInterruptWaiting() && fifo.bFF_GPReadEnable &&
                 fifo.CPReadWriteDistance && !AtBreakpoint())
          {
            if (param.bSyncGPU && s_sync_ticks.load() < param.iSyncGpuMinDistance)
              break;

            u32 cyclesExecuted = 0;
            u32 readPtr = fifo.CPReadPointer;
            ReadDataFromFifo(readPtr);

            if (readPtr == fifo.CPEnd)
              readPtr = fifo.CPBase;
            else
              readPtr += 32;

            _assert_msg_(COMMANDPROCESSOR, (s32)fifo.CPReadWriteDistance - 32 >= 0,
                         "Negative fifo.CPReadWriteDistance = %i in FIFO Loop !\nThat can produce "
                         "instability in the game. Please report it.",
                         fifo.CPReadWriteDistance - 32);

            u8* write_ptr = s_video_buffer_write_ptr;
            s_video_buffer_read_ptr = OpcodeDecoder::Run(
                DataReader(s_video_buffer_read_ptr, write_ptr), &cyclesExecuted, false);

            Common::AtomicStore(fifo.CPReadPointer, readPtr);
            Common::AtomicAdd(fifo.CPReadWriteDistance, -32);
            if ((write_ptr - s_video_buffer_read_ptr) == 0)
              Common::AtomicStore(fifo.SafeCPReadPointer, fifo.CPReadPointer);

            CommandProcessor::SetCPStatusFromGPU();

            if (param.bSyncGPU)
            {
              cyclesExecuted = (int)(cyclesExecuted / param.fSyncGpuOverclock);
              int old = s_sync_ticks.fetch_sub(cyclesExecuted);
              if (old > 0 && old - (int)cyclesExecuted <= 0)
                s_sync_wakeup_event.Set();
            }

            // This call is pretty important in DualCore mode and must be called in the FIFO Loop.
            // If we don't, s_swapRequested or s_efbAccessRequested won't be set to false
            // leading the CPU thread to wait in Video_BeginField or Video_AccessEFB thus slowing
            // things down.
            AsyncRequests::GetInstance()->PullEvents();
          }

          // fast skip remaining GPU time if fifo is empty
          if (s_sync_ticks.load() > 0)
          {
            int old = s_sync_ticks.exchange(0);
            if (old > 0)
              s_sync_wakeup_event.Set();
          }

          // The fifo is empty and it's unlikely we will get any more work in the near future.
          // Make sure VertexManager finishes drawing any primitives it has stored in it's buffer.
          VertexManagerBase::Flush();
        }
      },
      100);

  AsyncRequests::GetInstance()->SetEnable(false);
  AsyncRequests::GetInstance()->SetPassthrough(true);
}

void FlushGpu()
{
  const SConfig& param = SConfig::GetInstance();

  if (!param.bCPUThread || s_use_deterministic_gpu_thread)
    return;

  s_gpu_mainloop.Wait();
}

void GpuMaySleep()
{
  s_gpu_mainloop.AllowSleep();
}

bool AtBreakpoint()
{
  SCPFifoStruct& fifo = CommandProcessor::fifo;
  return fifo.bFF_BPEnable && (fifo.CPReadPointer == fifo.CPBreakpoint);
}

void RunGpu()
{
  SCPFifoStruct& fifo = CommandProcessor::fifo;
  const SConfig& param = SConfig::GetInstance();

  // execute GPU
  if (!param.bCPUThread || s_use_deterministic_gpu_thread)
  {
    bool reset_simd_state = false;
    while (fifo.bFF_GPReadEnable && fifo.CPReadWriteDistance && !AtBreakpoint())
    {
      if (s_use_deterministic_gpu_thread)
      {
        ReadDataFromFifoOnCPU(fifo.CPReadPointer);
        s_gpu_mainloop.Wakeup();
      }
      else
      {
        if (!reset_simd_state)
        {
          FPURoundMode::SaveSIMDState();
          FPURoundMode::LoadDefaultSIMDState();
          reset_simd_state = true;
        }
        ReadDataFromFifo(fifo.CPReadPointer);
        s_video_buffer_read_ptr = OpcodeDecoder::Run(
            DataReader(s_video_buffer_read_ptr, s_video_buffer_write_ptr), nullptr, false);
      }

      // DEBUG_LOG(COMMANDPROCESSOR, "Fifo wraps to base");

      if (fifo.CPReadPointer == fifo.CPEnd)
        fifo.CPReadPointer = fifo.CPBase;
      else
        fifo.CPReadPointer += 32;

      fifo.CPReadWriteDistance -= 32;
    }
    CommandProcessor::SetCPStatusFromGPU();

    if (reset_simd_state)
    {
      FPURoundMode::LoadSIMDState();
    }
  }

  // wake up GPU thread
  if (param.bCPUThread)
  {
    s_gpu_mainloop.Wakeup();
  }
}

void UpdateWantDeterminism(bool want)
{
  // We are paused (or not running at all yet), so
  // it should be safe to change this.
  const SConfig& param = SConfig::GetInstance();
  bool gpu_thread = false;
  switch (param.m_GPUDeterminismMode)
  {
  case GPU_DETERMINISM_AUTO:
    gpu_thread = want;

    // Hack: For now movies are an exception to this being on (but not
    // to wanting determinism in general).  Once vertex arrays are
    // fixed, there should be no reason to want this off for movies by
    // default, so this can be removed.
    if (!NetPlay::IsNetPlayRunning())
      gpu_thread = false;

    break;
  case GPU_DETERMINISM_NONE:
    gpu_thread = false;
    break;
  case GPU_DETERMINISM_FAKE_COMPLETION:
    gpu_thread = true;
    break;
  }

  gpu_thread = gpu_thread && param.bCPUThread;

  if (s_use_deterministic_gpu_thread != gpu_thread)
  {
    s_use_deterministic_gpu_thread = gpu_thread;
    if (gpu_thread)
    {
      // These haven't been updated in non-deterministic mode.
      s_video_buffer_seen_ptr = s_video_buffer_pp_read_ptr = s_video_buffer_read_ptr;
      CopyPreprocessCPStateFromMain();
      VertexLoaderManager::MarkAllDirty();
    }
  }
}

bool UseDeterministicGPUThread()
{
  return s_use_deterministic_gpu_thread;
}

/* This function checks the emulated CPU - GPU distance and may wake up the GPU,
 * or block the CPU if required. It should be called by the CPU thread regulary.
 * @ticks The gone emulated CPU time.
 * @return A good time to call Update() next.
 */
static int Update(int ticks)
{
  const SConfig& param = SConfig::GetInstance();

  // GPU is sleeping, so no need for synchronization
  if (s_gpu_mainloop.IsDone() || s_use_deterministic_gpu_thread)
  {
    if (s_sync_ticks.load() < 0)
    {
      int old = s_sync_ticks.fetch_add(ticks);
      if (old < param.iSyncGpuMinDistance && old + ticks >= param.iSyncGpuMinDistance)
        RunGpu();
    }
    return param.iSyncGpuMaxDistance;
  }

  // Wakeup GPU
  int old = s_sync_ticks.fetch_add(ticks);
  if (old < param.iSyncGpuMinDistance && old + ticks >= param.iSyncGpuMinDistance)
    RunGpu();

  // Wait for GPU
  if (s_sync_ticks.load() >= param.iSyncGpuMaxDistance)
  {
    while (s_sync_ticks.load() > 0)
    {
      s_sync_wakeup_event.Wait();
    }
  }

  return param.iSyncGpuMaxDistance - s_sync_ticks.load();
}

static void SyncGPUCallback(u64 userdata, s64 cyclesLate)
{
  u64 now = CoreTiming::GetTicks();
  int next = Fifo::Update((int)(now - s_last_sync_gpu_tick));
  s_last_sync_gpu_tick = now;

  if (next > 0)
    CoreTiming::ScheduleEvent(next, s_event_sync_gpu);
}

// Initialize GPU - CPU thread syncing, this gives us a deterministic way to start the GPU thread.
void Prepare()
{
  if (SConfig::GetInstance().bCPUThread && SConfig::GetInstance().bSyncGPU)
  {
    s_event_sync_gpu = CoreTiming::RegisterEvent("SyncGPUCallback", SyncGPUCallback);
    CoreTiming::ScheduleEvent(0, s_event_sync_gpu);
    s_last_sync_gpu_tick = CoreTiming::GetTicks();
  }
}
}