From 74905b269ba2e4d215d8e1669f20c6b6cc6e370e Mon Sep 17 00:00:00 2001 From: James Liu Date: Tue, 20 Dec 2022 01:59:07 +0000 Subject: [PATCH] Shrink DrawFunctionId (#6944) # Objective This includes one part of #4899. The aim is to improve CPU-side rendering performance by reducing the memory footprint and bandwidth required. ## Solution Shrink `DrawFunctionId` to `u32`. Enforce that `u32 as usize` conversions are always safe by forbidding compilation on 16-bit platforms. This shouldn't be a breaking change since #4736 disabled compilation of `bevy_ecs` on those platforms. Shrinking `DrawFunctionId` shrinks all of the `PhaseItem` types, which is integral to sort and render phase performance. Testing against `many_cubes`, the sort phase improved by 22% (174.21us -> 141.76us per frame). ![image](https://user-images.githubusercontent.com/3137680/207345422-a512b4cf-1680-46e0-9973-ea72494ebdfe.png) The main opaque pass also imrproved by 9% (5.49ms -> 5.03ms) ![image](https://user-images.githubusercontent.com/3137680/207346436-cbee7209-6450-4964-b566-0b64cfa4b4ea.png) Overall frame time improved by 5% (14.85ms -> 14.09ms) ![image](https://user-images.githubusercontent.com/3137680/207346895-9de8676b-ef37-4cb9-8445-8493f5f90003.png) There will be a followup PR that likewise shrinks `CachedRenderPipelineId` which should yield similar results on top of these improvements. --- crates/bevy_render/src/lib.rs | 3 +++ crates/bevy_render/src/render_phase/draw.rs | 6 +++--- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/crates/bevy_render/src/lib.rs b/crates/bevy_render/src/lib.rs index f595023588e768..5f3e4140687588 100644 --- a/crates/bevy_render/src/lib.rs +++ b/crates/bevy_render/src/lib.rs @@ -1,3 +1,6 @@ +#[cfg(target_pointer_width = "16")] +compile_error!("bevy_render cannot compile for a 16-bit platform."); + extern crate core; pub mod camera; diff --git a/crates/bevy_render/src/render_phase/draw.rs b/crates/bevy_render/src/render_phase/draw.rs index 67ff987b7972d4..14930b1931ffa2 100644 --- a/crates/bevy_render/src/render_phase/draw.rs +++ b/crates/bevy_render/src/render_phase/draw.rs @@ -65,7 +65,7 @@ pub trait PhaseItem: Sized + Send + Sync + 'static { // TODO: make this generic? /// An identifier for a [`Draw`] function stored in [`DrawFunctions`]. #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)] -pub struct DrawFunctionId(usize); +pub struct DrawFunctionId(u32); /// Stores all draw functions for the [`PhaseItem`] type. /// For retrieval they are associated with their [`TypeId`]. @@ -82,15 +82,15 @@ impl DrawFunctionsInternal

{ /// Adds the [`Draw`] function and associates it to the type `T` pub fn add_with>(&mut self, draw_function: D) -> DrawFunctionId { + let id = DrawFunctionId(self.draw_functions.len().try_into().unwrap()); self.draw_functions.push(Box::new(draw_function)); - let id = DrawFunctionId(self.draw_functions.len() - 1); self.indices.insert(TypeId::of::(), id); id } /// Retrieves the [`Draw`] function corresponding to the `id` mutably. pub fn get_mut(&mut self, id: DrawFunctionId) -> Option<&mut dyn Draw

> { - self.draw_functions.get_mut(id.0).map(|f| &mut **f) + self.draw_functions.get_mut(id.0 as usize).map(|f| &mut **f) } /// Retrieves the id of the [`Draw`] function corresponding to their associated type `T`.