Implement minimal emulation of TMEM caching

This is a remake of https://github.com/dolphin-emu/dolphin/pull/3749

Full credit goes to phire.

Old message:
"If none of the texture registers have changed and TMEM hasn't been invalidated or changed in other ways, we can blindly reuse the old texture cache entries without rehashing.

Not only does this fix the bloom effect in Spyro: A Hero's Tail (The game abused texture cache) but it will also provide speedups for other games which use the same texture over multiple draw calls, especially when safe texture cache is in use."

Changed the pr per phire's instructions to only return the current texture(s) if none of the texture registers were changed. If any texture register was changed, fall back to the default hashing and rebuilding textures from memory.

Source/Core/VideoCommon/BPStructs.cpp

@@ -285,6 +285,8 @@ static void BPWritten(const BPCmd& bp)
     if (g_bRecordFifoData)
       FifoRecorder::GetInstance().UseMemory(addr, tlutXferCount, MemoryUpdate::TMEM);
 
+    TextureCacheBase::InvalidateAllBindPoints();
+
     return;
   }
   case BPMEM_FOGRANGE:  // Fog Settings Control
@@ -397,6 +399,7 @@ static void BPWritten(const BPCmd& bp)
     return;
   case BPMEM_TEXINVALIDATE:
     // TODO: Needs some restructuring in TextureCacheBase.
+    TextureCacheBase::InvalidateAllBindPoints();
     return;
 
   case BPMEM_ZCOMPARE:  // Set the Z-Compare and EFB pixel format
@@ -499,6 +502,8 @@ static void BPWritten(const BPCmd& bp)
 
       if (g_bRecordFifoData)
         FifoRecorder::GetInstance().UseMemory(src_addr, bytes_read, MemoryUpdate::TMEM);
+
+      TextureCacheBase::InvalidateAllBindPoints();
     }
     return;
 
@@ -582,10 +587,12 @@ static void BPWritten(const BPCmd& bp)
   // ------------------------
   case BPMEM_TX_SETMODE0:  // (0x90 for linear)
   case BPMEM_TX_SETMODE0_4:
+    TextureCacheBase::InvalidateAllBindPoints();
     return;
 
   case BPMEM_TX_SETMODE1:
   case BPMEM_TX_SETMODE1_4:
+    TextureCacheBase::InvalidateAllBindPoints();
     return;
   // --------------------------------------------
   // BPMEM_TX_SETIMAGE0 - Texture width, height, format
@@ -602,6 +609,7 @@ static void BPWritten(const BPCmd& bp)
   case BPMEM_TX_SETIMAGE2_4:
   case BPMEM_TX_SETIMAGE3:
   case BPMEM_TX_SETIMAGE3_4:
+    TextureCacheBase::InvalidateAllBindPoints();
     return;
   // -------------------------------
   // Set a TLUT
@@ -609,6 +617,7 @@ static void BPWritten(const BPCmd& bp)
   // -------------------------------
   case BPMEM_TX_SETTLUT:
   case BPMEM_TX_SETTLUT_4:
+    TextureCacheBase::InvalidateAllBindPoints();
     return;
 
   default:

Source/Core/VideoCommon/TextureCacheBase.cpp

@@ -42,6 +42,8 @@ static const int TEXTURE_POOL_KILL_THRESHOLD = 3;
 
 std::unique_ptr<TextureCacheBase> g_texture_cache;
 
+std::bitset<8> TextureCacheBase::valid_bind_points;
+
 TextureCacheBase::TCacheEntry::TCacheEntry(std::unique_ptr<AbstractTexture> tex)
     : texture(std::move(tex))
 {
@@ -76,11 +78,17 @@ TextureCacheBase::TextureCacheBase()
   HiresTexture::Init();
 
   SetHash64Function();
+
+  InvalidateAllBindPoints();
 }
 
 void TextureCacheBase::Invalidate()
 {
-  UnbindTextures();
+  InvalidateAllBindPoints();
+  for (size_t i = 0; i < bound_textures.size(); ++i)
+  {
+    bound_textures[i] = nullptr;
+  }
 
   for (auto& tex : textures_by_address)
   {
@@ -138,7 +146,11 @@ void TextureCacheBase::Cleanup(int _frameCount)
   TexAddrCache::iterator tcend = textures_by_address.end();
   while (iter != tcend)
   {
-    if (iter->second->frameCount == FRAMECOUNT_INVALID)
+    if (iter->second->tmem_only)
+    {
+      iter = InvalidateTexture(iter);
+    }
+    else if (iter->second->frameCount == FRAMECOUNT_INVALID)
     {
       iter->second->frameCount = _frameCount;
       ++iter;
@@ -307,7 +319,7 @@ TextureCacheBase::DoPartialTextureUpdates(TCacheEntry* entry_to_update, u8* pale
   while (iter.first != iter.second)
   {
     TCacheEntry* entry = iter.first->second;
-    if (entry != entry_to_update && entry->IsEfbCopy() &&
+    if (entry != entry_to_update && entry->IsEfbCopy() && !entry->tmem_only &&
         entry->references.count(entry_to_update) == 0 &&
         entry->OverlapsMemoryRange(entry_to_update->addr, entry_to_update->size_in_bytes) &&
         entry->memory_stride == numBlocksX * block_size)
@@ -450,6 +462,9 @@ TextureCacheBase::TCacheEntry* TextureCacheBase::ReturnEntry(unsigned int stage,
 
   GFX_DEBUGGER_PAUSE_AT(NEXT_TEXTURE_CHANGE, true);
 
+  // We need to keep track of invalided textures until they have actually been replaced or re-loaded
+  valid_bind_points.set(stage);
+
   return entry;
 }
 
@@ -457,18 +472,19 @@ void TextureCacheBase::BindTextures()
 {
   for (size_t i = 0; i < bound_textures.size(); ++i)
   {
-    if (bound_textures[i])
+    if (IsValidBindPoint(static_cast<u32>(i)) && bound_textures[i])
       bound_textures[i]->texture->Bind(static_cast<u32>(i));
   }
 }
 
-void TextureCacheBase::UnbindTextures()
-{
-  bound_textures.fill(nullptr);
-}
-
 TextureCacheBase::TCacheEntry* TextureCacheBase::Load(const u32 stage)
 {
+  // if this stage was not invalidated by changes to texture registers, keep the current texture
+  if (IsValidBindPoint(stage) && bound_textures[stage])
+  {
+    return ReturnEntry(stage, bound_textures[stage]);
+  }
+
   const FourTexUnits& tex = bpmem.tex[stage >> 2];
   const u32 id = stage & 3;
   const u32 address = (tex.texImage3[id].image_base /* & 0x1FFFFF*/) << 5;
@@ -610,6 +626,14 @@ TextureCacheBase::TCacheEntry* TextureCacheBase::Load(const u32 stage)
   while (iter != iter_range.second)
   {
     TCacheEntry* entry = iter->second;
+
+    // Skip entries that are only left in our texture cache for the tmem cache emulation
+    if (entry->tmem_only)
+    {
+      ++iter;
+      continue;
+    }
+
     // Do not load strided EFB copies, they are not meant to be used directly
     if (entry->IsEfbCopy() && entry->native_width == nativeW && entry->native_height == nativeH &&
         entry->memory_stride == entry->BytesPerRow())
@@ -1466,6 +1490,18 @@ TextureCacheBase::InvalidateTexture(TexAddrCache::iterator iter)
     entry->textures_by_hash_iter = textures_by_hash.end();
   }
 
+  for (size_t i = 0; i < bound_textures.size(); ++i)
+  {
+    // If the entry is currently bound and not invalidated, keep it, but mark it as invalidated.
+    // This way it can still be used via tmem cache emulation, but nothing else.
+    // Spyro: A Hero's Tail is known for using such overwritten textures.
+    if (bound_textures[i] == entry && IsValidBindPoint(static_cast<u32>(i)))
+    {
+      bound_textures[i]->tmem_only = true;
+      return ++iter;
+    }
+  }
+
   auto config = entry->texture->GetConfig();
   texture_pool.emplace(config, TexPoolEntry(std::move(entry->texture)));
 

Source/Core/VideoCommon/TextureCacheBase.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <array>
+#include <bitset>
 #include <map>
 #include <memory>
 #include <tuple>
@@ -39,6 +40,7 @@ public:
     bool is_efb_copy;
     bool is_custom_tex;
     bool may_have_overlapping_textures = true;
+    bool tmem_only = false;  // indicates that this texture only exists in the tmem cache
 
     unsigned int native_width,
         native_height;  // Texture dimensions from the GameCube's point of view
@@ -125,8 +127,9 @@ public:
   virtual void DeleteShaders() = 0;
 
   TCacheEntry* Load(const u32 stage);
-  void UnbindTextures();
-  virtual void BindTextures();
+  static void InvalidateAllBindPoints() { valid_bind_points.reset(); }
+  static bool IsValidBindPoint(u32 i) { return valid_bind_points.test(i); }
+  void BindTextures();
   void CopyRenderTargetToTexture(u32 dstAddr, unsigned int dstFormat, u32 dstStride,
                                  bool is_depth_copy, const EFBRectangle& srcRect, bool isIntensity,
                                  bool scaleByHalf);
@@ -158,6 +161,7 @@ protected:
   size_t temp_size = 0;
 
   std::array<TCacheEntry*, 8> bound_textures{};
+  static std::bitset<8> valid_bind_points;
 
 private:
   // Minimal version of TCacheEntry just for TexPool

Source/Core/VideoCommon/VertexManagerBase.cpp

@@ -243,7 +243,6 @@ void VertexManagerBase::Flush()
         if (bpmem.tevind[i].IsActive() && bpmem.tevind[i].bt < bpmem.genMode.numindstages)
           usedtextures[bpmem.tevindref.getTexMap(bpmem.tevind[i].bt)] = true;
 
-    g_texture_cache->UnbindTextures();
     for (unsigned int i : usedtextures)
     {
       const auto* tentry = g_texture_cache->Load(i);