gl_rasterizer_cache: Use dirty flags for color buffers

src/video_core/engines/maxwell_3d.cpp

@@ -135,6 +135,15 @@ void Maxwell3D::CallMethod(const GPU::MethodCall& method_call) {
 
     if (regs.reg_array[method_call.method] != method_call.argument) {
         regs.reg_array[method_call.method] = method_call.argument;
+        // Color buffers
+        constexpr u32 first_rt_reg = MAXWELL3D_REG_INDEX(rt);
+        constexpr u32 registers_per_rt = sizeof(regs.rt[0]) / sizeof(u32);
+        if (method_call.method >= first_rt_reg &&
+            method_call.method < first_rt_reg + registers_per_rt * Regs::NumRenderTargets) {
+            const std::size_t rt_index = (method_call.method - first_rt_reg) / registers_per_rt;
+            dirty_flags.color_buffer |= 1u << static_cast<u32>(rt_index);
+        }
+
         // Shader
         constexpr u32 shader_registers_count =
             sizeof(regs.shader_config[0]) * Regs::MaxShaderProgram / sizeof(u32);

src/video_core/engines/maxwell_3d.h

@@ -1089,12 +1089,15 @@ public:
     MemoryManager& memory_manager;
 
     struct DirtyFlags {
+        u8 color_buffer = 0xFF;
+
         bool shaders = true;
 
         bool vertex_attrib_format = true;
         u32 vertex_array = 0xFFFFFFFF;
 
         void OnMemoryWrite() {
+            color_buffer = 0xFF;
             shaders = true;
             vertex_array = 0xFFFFFFFF;
         }

src/video_core/renderer_opengl/gl_rasterizer_cache.cpp

@@ -933,21 +933,27 @@ Surface RasterizerCacheOpenGL::GetDepthBufferSurface(bool preserve_contents) {
 }
 
 Surface RasterizerCacheOpenGL::GetColorBufferSurface(std::size_t index, bool preserve_contents) {
-    const auto& regs{Core::System::GetInstance().GPU().Maxwell3D().regs};
+    auto& gpu{Core::System::GetInstance().GPU().Maxwell3D()};
+    const auto& regs{gpu.regs};
+
+    if ((gpu.dirty_flags.color_buffer & (1u << static_cast<u32>(index))) == 0) {
+        return last_color_buffers[index];
+    }
+    gpu.dirty_flags.color_buffer &= ~(1u << static_cast<u32>(index));
 
     ASSERT(index < Tegra::Engines::Maxwell3D::Regs::NumRenderTargets);
 
     if (index >= regs.rt_control.count) {
-        return {};
+        return last_color_buffers[index] = {};
     }
 
     if (regs.rt[index].Address() == 0 || regs.rt[index].format == Tegra::RenderTargetFormat::NONE) {
-        return {};
+        return last_color_buffers[index] = {};
     }
 
     const SurfaceParams color_params{SurfaceParams::CreateForFramebuffer(index)};
 
-    return GetSurface(color_params, preserve_contents);
+    return last_color_buffers[index] = GetSurface(color_params, preserve_contents);
 }
 
 void RasterizerCacheOpenGL::LoadSurface(const Surface& surface) {

src/video_core/renderer_opengl/gl_rasterizer_cache.h

@@ -396,6 +396,8 @@ private:
     /// Use a Pixel Buffer Object to download the previous texture and then upload it to the new one
     /// using the new format.
     OGLBuffer copy_pbo;
+
+    std::array<Surface, Tegra::Engines::Maxwell3D::Regs::NumRenderTargets> last_color_buffers;
 };
 
 } // namespace OpenGL