RasterizerCache: Do not flush surfaces that have not been modified.

This should bring the performance closer to what it was before flushing was implemented.

src/video_core/renderer_opengl/gl_rasterizer.cpp

@@ -322,6 +322,13 @@ void RasterizerOpenGL::ConfigureFramebuffers(bool using_color_fb, bool using_dep
             // Used when just a single color attachment is enabled, e.g. for clearing a color buffer
             Surface color_surface =
                 res_cache.GetColorBufferSurface(*single_color_target, preserve_contents);
+
+            if (color_surface) {
+                // Assume that a surface will be written to if it is used as a framebuffer, even if
+                // the shader doesn't actually write to it.
+                color_surface->MarkAsDirty();
+            }
+
             glFramebufferTexture2D(
                 GL_DRAW_FRAMEBUFFER,
                 GL_COLOR_ATTACHMENT0 + static_cast<GLenum>(*single_color_target), GL_TEXTURE_2D,
@@ -332,6 +339,11 @@ void RasterizerOpenGL::ConfigureFramebuffers(bool using_color_fb, bool using_dep
             std::array<GLenum, Maxwell::NumRenderTargets> buffers;
             for (std::size_t index = 0; index < Maxwell::NumRenderTargets; ++index) {
                 Surface color_surface = res_cache.GetColorBufferSurface(index, preserve_contents);
+                if (color_surface) {
+                    // Assume that a surface will be written to if it is used as a framebuffer, even
+                    // if the shader doesn't actually write to it.
+                    color_surface->MarkAsDirty();
+                }
                 buffers[index] = GL_COLOR_ATTACHMENT0 + regs.rt_control.GetMap(index);
                 glFramebufferTexture2D(
                     GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + static_cast<GLenum>(index),
@@ -351,6 +363,12 @@ void RasterizerOpenGL::ConfigureFramebuffers(bool using_color_fb, bool using_dep
     }
 
     if (depth_surface) {
+        if (depth_surface) {
+            // Assume that a surface will be written to if it is used as a framebuffer, even if
+            // the shader doesn't actually write to it.
+            depth_surface->MarkAsDirty();
+        }
+
         if (regs.stencil_enable) {
             // Attach both depth and stencil
             glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_TEXTURE_2D,

src/video_core/renderer_opengl/gl_rasterizer_cache.cpp

@@ -638,12 +638,18 @@ void CachedSurface::LoadGLBuffer() {
     }
 
     ConvertFormatAsNeeded_LoadGLBuffer(gl_buffer, params.pixel_format, params.width, params.height);
+
+    dirty = false;
 }
 
 MICROPROFILE_DEFINE(OpenGL_SurfaceFlush, "OpenGL", "Surface Flush", MP_RGB(128, 192, 64));
 void CachedSurface::FlushGLBuffer() {
     MICROPROFILE_SCOPE(OpenGL_SurfaceFlush);
 
+    // There is no need to flush the surface if it hasn't been modified by us.
+    if (!dirty)
+        return;
+
     const auto& rect{params.GetRect()};
 
     // Load data from memory to the surface
@@ -700,6 +706,8 @@ void CachedSurface::FlushGLBuffer() {
         Memory::WriteBlock(params.addr + buffer_offset, &gl_buffer[buffer_offset],
                            gl_buffer.size() - buffer_offset);
     }
+
+    dirty = false;
 }
 
 MICROPROFILE_DEFINE(OpenGL_TextureUL, "OpenGL", "Texture Upload", MP_RGB(128, 64, 192));

src/video_core/renderer_opengl/gl_rasterizer_cache.h

@@ -745,6 +745,10 @@ public:
         FlushGLBuffer();
     }
 
+    void MarkAsDirty() {
+        dirty = true;
+    }
+
     const OGLTexture& Texture() const {
         return texture;
     }
@@ -776,6 +780,7 @@ private:
     std::vector<u8> gl_buffer;
     SurfaceParams params;
     GLenum gl_target;
+    bool dirty = false;
 };
 
 class RasterizerCacheOpenGL final : public RasterizerCache<Surface> {