[Impeller] store vertex buffers in render pass for gles. (flutter/engine#56991)

Move vertex buffer storage off of the command object. Because we can bind up to 16 (but usually 1) vertex buffers per cmd, storing it on the command requires allocating storage for the full 16 buffers. MOving this to a secondary vector decreases the size of the command object from ~800 bytes to ~200 bytes.

Author: Jonah Williams

engine/src/flutter/impeller/entity/contents/test/recording_render_pass.cc

@@ -74,7 +74,6 @@ void RecordingRenderPass::SetInstanceCount(size_t count) {
 
 // |RenderPass|
 bool RecordingRenderPass::SetVertexBuffer(VertexBuffer buffer) {
-  pending_.BindVertices(buffer);
   if (delegate_) {
     return delegate_->SetVertexBuffer(buffer);
   }

engine/src/flutter/impeller/renderer/backend/gles/render_pass_gles.cc

@@ -10,6 +10,7 @@
 #include "fml/closure.h"
 #include "fml/logging.h"
 #include "impeller/base/validation.h"
+#include "impeller/core/buffer_view.h"
 #include "impeller/core/formats.h"
 #include "impeller/renderer/backend/gles/buffer_bindings_gles.h"
 #include "impeller/renderer/backend/gles/context_gles.h"
@@ -191,6 +192,7 @@ void RenderPassGLES::ResetGLState(const ProcTableGLES& gl) {
     const RenderPassData& pass_data,
     const ReactorGLES& reactor,
     const std::vector<Command>& commands,
+    const std::vector<BufferView>& vertex_buffers,
     const std::vector<TextureAndSampler>& bound_textures,
     const std::vector<BufferResource>& bound_buffers,
     const std::shared_ptr<GPUTracerGLES>& tracer) {
@@ -441,8 +443,9 @@ void RenderPassGLES::ResetGLState(const ProcTableGLES& gl) {
     ///       `RenderPass::ValidateIndexBuffer` here, as validation already runs
     ///       when the vertex/index buffers are set on the command.
     ///
-    for (size_t i = 0; i < command.vertex_buffer_count; i++) {
-      if (!BindVertexBuffer(gl, vertex_desc_gles, command.vertex_buffers[i],
+    for (size_t i = 0; i < command.vertex_buffers.length; i++) {
+      if (!BindVertexBuffer(gl, vertex_desc_gles,
+                            vertex_buffers[i + command.vertex_buffers.offset],
                             i)) {
         return false;
       }
@@ -615,6 +618,7 @@ bool RenderPassGLES::OnEncodeCommands(const Context& context) const {
             /*pass_data=*/*pass_data,                         //
             /*reactor=*/reactor,                              //
             /*commands=*/render_pass->commands_,              //
+            /*vertex_buffers=*/render_pass->vertex_buffers_,  //
             /*bound_textures=*/render_pass->bound_textures_,  //
             /*bound_buffers=*/render_pass->bound_buffers_,    //
             /*tracer=*/tracer                                 //

engine/src/flutter/impeller/renderer/command.cc

@@ -4,23 +4,8 @@
 
 #include "impeller/renderer/command.h"
 
-#include "impeller/base/validation.h"
-#include "impeller/core/formats.h"
-
 namespace impeller {
 
-bool Command::BindVertices(const VertexBuffer& buffer) {
-  if (buffer.index_type == IndexType::kUnknown) {
-    VALIDATION_LOG << "Cannot bind vertex buffer with an unknown index type.";
-    return false;
-  }
-
-  vertex_buffers = {buffer.vertex_buffer};
-  vertex_buffer_count = 1u;
-  element_count = buffer.vertex_count;
-  index_buffer = buffer.index_buffer;
-  index_type = buffer.index_type;
-  return true;
-}
+//
 
 }  // namespace impeller

engine/src/flutter/impeller/renderer/command.h

@@ -15,7 +15,6 @@
 #include "impeller/core/sampler.h"
 #include "impeller/core/shader_types.h"
 #include "impeller/core/texture.h"
-#include "impeller/core/vertex_buffer.h"
 #include "impeller/geometry/rect.h"
 #include "impeller/renderer/pipeline.h"
 
@@ -130,13 +129,10 @@ struct Command {
   size_t instance_count = 1u;
 
   //----------------------------------------------------------------------------
-  /// The vertex buffers used by the vertex shader stage.
-  std::array<BufferView, kMaxVertexBuffers> vertex_buffers;
-
-  //----------------------------------------------------------------------------
-  /// The number of vertex buffers in the vertex_buffers array. Must not exceed
-  /// kMaxVertexBuffers.
-  size_t vertex_buffer_count = 0u;
+  /// An offset and range of vertex buffers bound for this draw call.
+  ///
+  /// The vertex buffers are stored on the render pass object.
+  Range vertex_buffers;
 
   //----------------------------------------------------------------------------
   /// The index buffer binding used by the vertex shader stage.
@@ -152,16 +148,6 @@ struct Command {
   /// packed in the index buffer.
   IndexType index_type = IndexType::kUnknown;
 
-  //----------------------------------------------------------------------------
-  /// @brief      Specify the vertex and index buffer to use for this command.
-  ///
-  /// @param[in]  buffer  The vertex and index buffer definition. If possible,
-  ///             this value should be moved and not copied.
-  ///
-  /// @return     returns if the binding was updated.
-  ///
-  bool BindVertices(const VertexBuffer& buffer);
-
   bool IsValid() const { return pipeline && pipeline->IsValid(); }
 };
 

engine/src/flutter/impeller/renderer/render_pass.cc

@@ -142,9 +142,13 @@ bool RenderPass::SetVertexBuffer(BufferView vertex_buffers[],
     return false;
   }
 
-  pending_.vertex_buffer_count = vertex_buffer_count;
+  if (!vertex_buffers_start_.has_value()) {
+    vertex_buffers_start_ = vertex_buffers_.size();
+  }
+
+  pending_.vertex_buffers.length += vertex_buffer_count;
   for (size_t i = 0; i < vertex_buffer_count; i++) {
-    pending_.vertex_buffers[i] = std::move(vertex_buffers[i]);
+    vertex_buffers_.push_back(vertex_buffers[i]);
   }
   return true;
 }
@@ -196,10 +200,12 @@ bool RenderPass::ValidateIndexBuffer(const BufferView& index_buffer,
 fml::Status RenderPass::Draw() {
   pending_.bound_buffers.offset = bound_buffers_start_.value_or(0u);
   pending_.bound_textures.offset = bound_textures_start_.value_or(0u);
+  pending_.vertex_buffers.offset = vertex_buffers_start_.value_or(0u);
   auto result = AddCommand(std::move(pending_));
   pending_ = Command{};
   bound_textures_start_ = std::nullopt;
   bound_buffers_start_ = std::nullopt;
+  vertex_buffers_start_ = std::nullopt;
   if (result) {
     return fml::Status();
   }

engine/src/flutter/impeller/renderer/render_pass.h

@@ -244,6 +244,7 @@ class RenderPass : public ResourceBinder {
   const ISize render_target_size_;
   const RenderTarget render_target_;
   std::vector<Command> commands_;
+  std::vector<BufferView> vertex_buffers_;
   std::vector<BufferResource> bound_buffers_;
   std::vector<TextureAndSampler> bound_textures_;
   const Matrix orthographic_;
@@ -289,6 +290,7 @@ class RenderPass : public ResourceBinder {
   Command pending_;
   std::optional<size_t> bound_buffers_start_ = std::nullopt;
   std::optional<size_t> bound_textures_start_ = std::nullopt;
+  std::optional<size_t> vertex_buffers_start_ = std::nullopt;
 };
 
 }  // namespace impeller