gl_rasterizer: Upload constant buffers with glNamedBufferSubData

Nvidia's OpenGL driver maps gl(Named)BufferSubData with some requirements
to a fast. This path has an extra memcpy but updates the buffer without
orphaning or waiting for previous calls. It can be seen as a better
model for "push constants" that can upload a whole UBO instead of 256
bytes.

This path has some requirements established here:
http://on-demand.gputechconf.com/gtc/2014/presentations/S4379-opengl-44-scene-rendering-techniques.pdf#page=24

Instead of using the stream buffer, this commits moves constant buffers
uploads to calls of glNamedBufferSubData and from my testing it brings a
performance improvement. This is disabled when the vendor is not Nvidia
since it brings performance regressions.

1 files changed, 11 insertions, 3 deletions

diff --git a/src/video_core/buffer_cache/buffer_cache.h b/src/video_core/buffer_cache/buffer_cache.h
index 2442ddfd6..63b3a8205 100644
--- a/src/video_core/buffer_cache/buffer_cache.h
+++ b/src/video_core/buffer_cache/buffer_cache.h
@@ -30,7 +30,7 @@ public:
     using BufferInfo = std::pair<const TBufferType*, u64>;
 
     BufferInfo UploadMemory(GPUVAddr gpu_addr, std::size_t size, std::size_t alignment = 4,
-                            bool is_written = false) {
+                            bool is_written = false, bool use_fast_cbuf = false) {
         std::lock_guard lock{mutex};
 
         auto& memory_manager = system.GPU().MemoryManager();
@@ -43,9 +43,13 @@ public:
         // Cache management is a big overhead, so only cache entries with a given size.
         // TODO: Figure out which size is the best for given games.
         constexpr std::size_t max_stream_size = 0x800;
-        if (size < max_stream_size) {
+        if (use_fast_cbuf || size < max_stream_size) {
             if (!is_written && !IsRegionWritten(cache_addr, cache_addr + size - 1)) {
-                return StreamBufferUpload(host_ptr, size, alignment);
+                if (use_fast_cbuf) {
+                    return ConstBufferUpload(host_ptr, size);
+                } else {
+                    return StreamBufferUpload(host_ptr, size, alignment);
+                }
             }
         }
 
@@ -152,6 +156,10 @@ protected:
     virtual void CopyBlock(const TBuffer& src, const TBuffer& dst, std::size_t src_offset,
                            std::size_t dst_offset, std::size_t size) = 0;
 
+    virtual BufferInfo ConstBufferUpload(const void* raw_pointer, std::size_t size) {
+        return {};
+    }
+
     /// Register an object into the cache
     void Register(const MapInterval& new_map, bool inherit_written = false) {
         const CacheAddr cache_ptr = new_map->GetStart();