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https://github.com/libretro/Mesen.git
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PPU: Fixed reset state (started at cycle 1 instead of 0) + adjusted reset sync values (improves read2004 result).
+Simplified PPU code for a small performance boost (+3-6%)
This commit is contained in:
Souryo
parent
fa39dcbc80
commit
c477d75b66
@ -105,9 +105,10 @@ void CPU::Reset(bool softReset, NesModel model)
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}
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//The CPU takes some cycles before starting its execution after a reset/power up
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for(int i = 0; i < (model == NesModel::NTSC ? 12 : 15); i++) {
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PPU::ExecStatic();
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for(int i = 0; i < (model == NesModel::NTSC ? 28 : 30); i++) {
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PPU::RunOneCycle();
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}
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for(int i = 0; i < 10; i++) {
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APU::ExecStatic();
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}
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93
Core/PPU.cpp
93
Core/PPU.cpp
@ -71,6 +71,7 @@ void PPU::Reset()
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_prevRenderingEnabled = false;
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_cyclesNeeded = 0.0;
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memset(_hasSprite, 0, sizeof(_hasSprite));
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memset(_spriteTiles, 0, sizeof(SpriteInfo));
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_spriteCount = 0;
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_secondaryOAMAddr = 0;
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@ -81,8 +82,10 @@ void PPU::Reset()
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memset(_openBusDecayStamp, 0, sizeof(_openBusDecayStamp));
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_ignoreVramRead = 0;
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_scanline = 0;
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_cycle = 0;
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//First execution will be cycle 0, scanline 0
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_scanline = -1;
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_cycle = 340;
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_frameCount = 1;
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_memoryReadBuffer = 0;
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@ -515,9 +518,8 @@ void PPU::LoadTileInfo()
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_previousTile = _currentTile;
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_currentTile = _nextTile;
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if(_cycle > 1 && _cycle < 256) {
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LoadNextTile();
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}
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_state.LowBitShift |= _nextTile.LowByte;
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_state.HighBitShift |= _nextTile.HighByte;
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uint8_t tileIndex = _mapper->ReadVRAM(GetNameTableAddr());
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_nextTile.TileAddr = (tileIndex << 4) | (_state.VideoRamAddr >> 12) | _flags.BackgroundPatternAddr;
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@ -537,9 +539,6 @@ void PPU::LoadTileInfo()
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case 5:
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_nextTile.HighByte = _mapper->ReadVRAM(_nextTile.TileAddr + 8);
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if(_cycle == 334) {
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InitializeShiftRegisters();
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}
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break;
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}
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}
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@ -632,29 +631,17 @@ void PPU::LoadSpriteTileInfo()
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}
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}
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void PPU::LoadNextTile()
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{
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_state.LowBitShift |= _nextTile.LowByte;
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_state.HighBitShift |= _nextTile.HighByte;
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}
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void PPU::InitializeShiftRegisters()
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{
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_state.LowBitShift = (_currentTile.LowByte << 8) | _nextTile.LowByte;
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_state.HighBitShift = (_currentTile.HighByte << 8) | _nextTile.HighByte;
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}
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void PPU::ShiftTileRegisters()
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{
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_state.LowBitShift <<= 1;
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_state.HighBitShift <<= 1;
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}
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uint32_t PPU::GetPixelColor()
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uint8_t PPU::GetPixelColor()
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{
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uint8_t offset = _state.XScroll;
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uint32_t backgroundColor = 0;
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uint32_t spriteBgColor = 0;
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uint8_t backgroundColor = 0;
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uint8_t spriteBgColor = 0;
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if(_cycle > _minimumDrawBgCycle) {
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//BackgroundMask = false: Hide background in leftmost 8 pixels of screen
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@ -670,7 +657,7 @@ uint32_t PPU::GetPixelColor()
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int32_t shift = (int32_t)_cycle - _spriteTiles[i].SpriteX - 1;
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if(shift >= 0 && shift < 8) {
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_lastSprite = &_spriteTiles[i];
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uint32_t spriteColor;
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uint8_t spriteColor;
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if(_spriteTiles[i].HorizontalMirror) {
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spriteColor = ((_lastSprite->LowByte >> shift) & 0x01) | ((_lastSprite->HighByte >> shift) & 0x01) << 1;
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} else {
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@ -746,7 +733,8 @@ void PPU::UpdateGrayscaleAndIntensifyBits()
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void PPU::ProcessScanline()
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{
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if(_cycle > 0 && _cycle <= 256) {
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//Only called for cycle 1+
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if(_cycle <= 256) {
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LoadTileInfo();
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if(_prevRenderingEnabled && (_cycle & 0x07) == 0) {
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@ -763,6 +751,7 @@ void PPU::ProcessScanline()
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//"Secondary OAM clear and sprite evaluation do not occur on the pre-render line"
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ProcessSpriteEvaluation();
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} else if(_cycle < 9) {
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//Pre-render scanline logic
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if(_cycle == 1) {
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_statusFlags.VerticalBlank = false;
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}
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@ -814,6 +803,8 @@ void PPU::ProcessScanline()
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);
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}
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} else if(_prevRenderingEnabled && (_cycle == 328 || _cycle == 336)) {
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_state.LowBitShift <<= 8;
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_state.HighBitShift <<= 8;
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IncHorizontalScrolling();
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}
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} else if(_cycle == 337 || _cycle == 339) {
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@ -826,9 +817,6 @@ void PPU::ProcessScanline()
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_cycle = 340;
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}
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}
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} else if(_scanline == -1 && _cycle == 0) {
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_statusFlags.SpriteOverflow = false;
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_statusFlags.Sprite0Hit = false;
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}
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}
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@ -994,10 +982,8 @@ void PPU::SendFrame()
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void PPU::BeginVBlank()
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{
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if(_cycle == 0) {
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SendFrame();
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TriggerNmi();
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}
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SendFrame();
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TriggerNmi();
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}
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void PPU::TriggerNmi()
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@ -1011,31 +997,40 @@ void PPU::TriggerNmi()
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void PPU::Exec()
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{
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if(_cycle > 339) {
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_cycle = -1;
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_cycle = 0;
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if(++_scanline > _vblankEnd) {
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_lastUpdatedPixel = -1;
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_frameCount++;
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_scanline = -1;
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UpdateMinimumDrawCycles();
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}
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}
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_cycle++;
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Debugger::ProcessPpuCycle();
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Debugger::ProcessPpuCycle();
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if(_scanline < 240) {
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ProcessScanline();
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} else if(_scanline == _nmiScanline) {
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BeginVBlank();
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} else if(_nesModel == NesModel::PAL && _scanline >= _palSpriteEvalScanline) {
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//"On a PAL machine, because of its extended vertical blank, the PPU begins refreshing OAM roughly 21 scanlines after NMI[2], to prevent it
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//from decaying during the longer hiatus of rendering. Additionally, it will continue to refresh during the visible portion of the screen
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//even if rendering is disabled. Because of this, OAM DMA must be done near the beginning of vertical blank on PAL, and everywhere else
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//it is liable to conflict with the refresh. Since the refresh can't be disabled like on the NTSC hardware, OAM decay does not occur at all on the PAL NES."
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if(_cycle > 0 && _cycle <= 256) {
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ProcessSpriteEvaluation();
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} else if(_cycle >= 257 && _cycle < 320) {
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_state.SpriteRamAddr = 0;
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//Cycle = 0
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if(_scanline == -1) {
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_statusFlags.SpriteOverflow = false;
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_statusFlags.Sprite0Hit = false;
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} else if(_scanline == _nmiScanline) {
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BeginVBlank();
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}
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} else {
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//Cycle > 0
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_cycle++;
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Debugger::ProcessPpuCycle();
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if(_scanline < 240) {
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ProcessScanline();
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} else if(_nesModel == NesModel::PAL && _scanline >= _palSpriteEvalScanline) {
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//"On a PAL machine, because of its extended vertical blank, the PPU begins refreshing OAM roughly 21 scanlines after NMI[2], to prevent it
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//from decaying during the longer hiatus of rendering. Additionally, it will continue to refresh during the visible portion of the screen
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//even if rendering is disabled. Because of this, OAM DMA must be done near the beginning of vertical blank on PAL, and everywhere else
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//it is liable to conflict with the refresh. Since the refresh can't be disabled like on the NTSC hardware, OAM decay does not occur at all on the PAL NES."
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if(_cycle <= 256) {
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ProcessSpriteEvaluation();
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} else if(_cycle >= 257 && _cycle < 320) {
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_state.SpriteRamAddr = 0;
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}
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}
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}
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@ -126,15 +126,13 @@ class PPU : public IMemoryHandler, public Snapshotable
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void LoadSpriteTileInfo();
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void LoadExtraSprites();
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__forceinline void ShiftTileRegisters();
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void InitializeShiftRegisters();
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void LoadNextTile();
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__forceinline uint8_t ReadSpriteRam(uint8_t addr);
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__forceinline void WriteSpriteRam(uint8_t addr, uint8_t value);
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void UpdateMinimumDrawCycles();
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__forceinline uint32_t GetPixelColor();
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__forceinline uint8_t GetPixelColor();
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__forceinline virtual void DrawPixel();
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void UpdateGrayscaleAndIntensifyBits();
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virtual void SendFrame();
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@ -182,6 +180,11 @@ class PPU : public IMemoryHandler, public Snapshotable
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void Exec();
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static void ExecStatic();
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static void RunOneCycle()
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{
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Instance->Exec();
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}
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static uint32_t GetFrameCount()
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{
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