hal: remove the cows

wgpu-core/src/command/render.rs

@@ -750,7 +750,7 @@ impl<'a, A: HalApi> RenderPassInfo<'a, A> {
 
         let hal_desc = hal::RenderPassDescriptor {
             label,
-            color_attachments: colors.iter().cloned().collect(),
+            color_attachments: &colors,
             depth_stencil_attachment: depth_stencil,
         };
         unsafe {

wgpu-core/src/device/mod.rs

@@ -11,8 +11,7 @@ use crate::{
     pipeline, resource, swap_chain,
     track::{BufferState, TextureSelector, TextureState, TrackerSet, UsageConflict},
     validation::{self, check_buffer_usage, check_texture_usage},
-    CowHelpers as _, FastHashMap, Label, LabelHelpers as _, LifeGuard, MultiRefCount, Stored,
-    SubmissionIndex,
+    FastHashMap, Label, LabelHelpers as _, LifeGuard, MultiRefCount, Stored, SubmissionIndex,
 };
 
 use arrayvec::ArrayVec;
@@ -957,7 +956,7 @@ impl<A: HalApi> Device<A> {
         let hal_bindings = entry_map.values().cloned().collect::<Vec<_>>();
         let hal_desc = hal::BindGroupLayoutDescriptor {
             label,
-            entries: Cow::Owned(hal_bindings),
+            entries: &hal_bindings,
         };
         let raw = unsafe {
             self.raw
@@ -1432,7 +1431,7 @@ impl<A: HalApi> Device<A> {
         let hal_desc = hal::BindGroupDescriptor {
             label: desc.label.borrow_option(),
             layout: &layout.raw,
-            entries: hal_entries.into(),
+            entries: &hal_entries,
         };
         let raw = unsafe {
             self.raw
@@ -1522,14 +1521,15 @@ impl<A: HalApi> Device<A> {
             .validate(&self.limits)
             .map_err(Error::TooManyBindings)?;
 
+        let bgl_vec = desc
+            .bind_group_layouts
+            .iter()
+            .map(|&id| &bgl_guard.get(id).unwrap().raw)
+            .collect::<Vec<_>>();
         let hal_desc = hal::PipelineLayoutDescriptor {
             label: desc.label.borrow_option(),
-            bind_group_layouts: desc
-                .bind_group_layouts
-                .iter()
-                .map(|&id| &bgl_guard.get(id).unwrap().raw)
-                .collect(),
-            push_constant_ranges: desc.push_constant_ranges.reborrow(),
+            bind_group_layouts: &bgl_vec,
+            push_constant_ranges: desc.push_constant_ranges.as_ref(),
         };
 
         let raw = unsafe {
@@ -1688,7 +1688,7 @@ impl<A: HalApi> Device<A> {
             label: desc.label.borrow_option(),
             layout: &layout.raw,
             stage: hal::ProgrammableStage {
-                entry_point: desc.stage.entry_point.reborrow(),
+                entry_point: desc.stage.entry_point.as_ref(),
                 module: &shader_module.raw,
             },
         };
@@ -1779,7 +1779,7 @@ impl<A: HalApi> Device<A> {
             vertex_buffers.alloc().init(hal::VertexBufferLayout {
                 array_stride: vb_state.array_stride,
                 step_mode: vb_state.step_mode,
-                attributes: Cow::Borrowed(vb_state.attributes.as_ref()),
+                attributes: vb_state.attributes.as_ref(),
             });
 
             for attribute in vb_state.attributes.iter() {
@@ -1960,7 +1960,7 @@ impl<A: HalApi> Device<A> {
 
             hal::ProgrammableStage {
                 module: &shader_module.raw,
-                entry_point: stage.entry_point.reborrow(),
+                entry_point: stage.entry_point.as_ref(),
             }
         };
 
@@ -2005,7 +2005,7 @@ impl<A: HalApi> Device<A> {
 
                 Some(hal::ProgrammableStage {
                     module: &shader_module.raw,
-                    entry_point: fragment.stage.entry_point.reborrow(),
+                    entry_point: fragment.stage.entry_point.as_ref(),
                 })
             }
             None => None,
@@ -2063,13 +2063,13 @@ impl<A: HalApi> Device<A> {
         let pipeline_desc = hal::RenderPipelineDescriptor {
             label: desc.label.borrow_option(),
             layout: &layout.raw,
-            vertex_buffers: vertex_buffers.into(),
+            vertex_buffers: &vertex_buffers,
             vertex_stage,
             primitive: desc.primitive,
             depth_stencil: desc.depth_stencil.clone(),
             multisample: desc.multisample,
             fragment_stage,
-            color_targets: Cow::Borrowed(color_targets),
+            color_targets: color_targets,
         };
         let raw =
             unsafe { self.raw.create_render_pipeline(&pipeline_desc) }.map_err(

wgpu-core/src/lib.rs

@@ -76,15 +76,6 @@ impl<'a> LabelHelpers<'a> for Label<'a> {
     }
 }
 
-trait CowHelpers<'a> {
-    fn reborrow(&'a self) -> Self;
-}
-impl<'a, T: ToOwned + ?Sized> CowHelpers<'a> for Cow<'a, T> {
-    fn reborrow(&'a self) -> Self {
-        Cow::Borrowed(self.as_ref())
-    }
-}
-
 /// Reference count object that is 1:1 with each reference.
 #[derive(Debug)]
 struct RefCount(ptr::NonNull<AtomicUsize>);

wgpu-hal/examples/bunnymark/main.rs

@@ -2,13 +2,7 @@ extern crate wgpu_hal as hal;
 
 use hal::{Adapter as _, CommandBuffer as _, Device as _, Instance as _, Queue as _, Surface as _};
 
-use std::{
-    borrow::{Borrow, Cow},
-    iter, mem,
-    num::NonZeroU32,
-    ptr,
-    time::Instant,
-};
+use std::{borrow::Borrow, iter, mem, num::NonZeroU32, ptr, time::Instant};
 
 const MAX_BUNNIES: usize = 1 << 20;
 const BUNNY_SIZE: f32 = 0.15 * 256.0;
@@ -104,7 +98,7 @@ impl<A: hal::Api> Example<A> {
 
         let global_bgl_desc = hal::BindGroupLayoutDescriptor {
             label: None,
-            entries: Cow::Borrowed(&[
+            entries: &[
                 wgt::BindGroupLayoutEntry {
                     binding: 0,
                     visibility: wgt::ShaderStage::VERTEX,
@@ -134,14 +128,14 @@ impl<A: hal::Api> Example<A> {
                     },
                     count: None,
                 },
-            ]),
+            ],
         };
 
         let global_bind_group_layout =
             unsafe { device.create_bind_group_layout(&global_bgl_desc).unwrap() };
 
         let local_bgl_desc = hal::BindGroupLayoutDescriptor {
-            entries: Cow::Borrowed(&[wgt::BindGroupLayoutEntry {
+            entries: &[wgt::BindGroupLayoutEntry {
                 binding: 0,
                 visibility: wgt::ShaderStage::VERTEX,
                 ty: wgt::BindingType::Buffer {
@@ -150,7 +144,7 @@ impl<A: hal::Api> Example<A> {
                     min_binding_size: wgt::BufferSize::new(mem::size_of::<Locals>() as _),
                 },
                 count: None,
-            }]),
+            }],
             label: None,
         };
         let local_bind_group_layout =
@@ -158,11 +152,8 @@ impl<A: hal::Api> Example<A> {
 
         let pipeline_layout_desc = hal::PipelineLayoutDescriptor {
             label: None,
-            bind_group_layouts: Cow::Borrowed(&[
-                &global_bind_group_layout,
-                &local_bind_group_layout,
-            ]),
-            push_constant_ranges: Cow::Borrowed(&[]),
+            bind_group_layouts: &[&global_bind_group_layout, &local_bind_group_layout],
+            push_constant_ranges: &[],
         };
         let pipeline_layout = unsafe {
             device
@@ -175,12 +166,12 @@ impl<A: hal::Api> Example<A> {
             layout: &pipeline_layout,
             vertex_stage: hal::ProgrammableStage {
                 module: &shader,
-                entry_point: Cow::Borrowed("vs_main"),
+                entry_point: "vs_main",
             },
-            vertex_buffers: Cow::Borrowed(&[]),
+            vertex_buffers: &[],
             fragment_stage: Some(hal::ProgrammableStage {
                 module: &shader,
-                entry_point: Cow::Borrowed("fs_main"),
+                entry_point: "fs_main",
             }),
             primitive: wgt::PrimitiveState {
                 topology: wgt::PrimitiveTopology::TriangleStrip,
@@ -188,11 +179,11 @@ impl<A: hal::Api> Example<A> {
             },
             depth_stencil: None,
             multisample: wgt::MultisampleState::default(),
-            color_targets: Cow::Borrowed(&[wgt::ColorTargetState {
+            color_targets: &[wgt::ColorTargetState {
                 format: surface_config.format,
                 blend: Some(wgt::BlendState::ALPHA_BLENDING),
                 write_mask: wgt::ColorWrite::default(),
-            }]),
+            }],
         };
         let pipeline = unsafe { device.create_render_pipeline(&pipeline_desc).unwrap() };
 
@@ -341,7 +332,7 @@ impl<A: hal::Api> Example<A> {
             let global_group_desc = hal::BindGroupDescriptor {
                 label: Some("global"),
                 layout: &global_bind_group_layout,
-                entries: Cow::Borrowed(&[
+                entries: &[
                     hal::BindGroupEntry {
                         binding: 0,
                         resource: hal::BindingResource::Buffers(
@@ -359,7 +350,7 @@ impl<A: hal::Api> Example<A> {
                         binding: 2,
                         resource: hal::BindingResource::Sampler(&sampler),
                     },
-                ]),
+                ],
             };
             unsafe { device.create_bind_group(&global_group_desc).unwrap() }
         };
@@ -373,12 +364,12 @@ impl<A: hal::Api> Example<A> {
             let local_group_desc = hal::BindGroupDescriptor {
                 label: Some("local"),
                 layout: &local_bind_group_layout,
-                entries: Cow::Borrowed(&[hal::BindGroupEntry {
+                entries: &[hal::BindGroupEntry {
                     binding: 0,
                     resource: hal::BindingResource::Buffers(
                         iter::once(local_buffer_binding).collect(),
                     ),
-                }]),
+                }],
             };
             unsafe { device.create_bind_group(&local_group_desc).unwrap() }
         };
@@ -493,7 +484,7 @@ impl<A: hal::Api> Example<A> {
         };
         let pass_desc = hal::RenderPassDescriptor {
             label: None,
-            color_attachments: Cow::Borrowed(&[hal::ColorAttachment {
+            color_attachments: &[hal::ColorAttachment {
                 target: hal::Attachment {
                     view: &surface_tex_view,
                     usage: hal::TextureUse::COLOR_TARGET,
@@ -507,7 +498,7 @@ impl<A: hal::Api> Example<A> {
                     b: 0.3,
                     a: 1.0,
                 },
-            }]),
+            }],
             depth_stencil_attachment: None,
         };
         unsafe {

wgpu-hal/src/lib.rs

@@ -47,7 +47,7 @@ pub mod api {
 }
 
 use std::{
-    borrow::{Borrow, Cow},
+    borrow::Borrow,
     fmt,
     num::NonZeroU8,
     ops::{Range, RangeInclusive},
@@ -688,14 +688,14 @@ pub struct SamplerDescriptor<'a> {
 #[derive(Clone, Debug)]
 pub struct BindGroupLayoutDescriptor<'a> {
     pub label: Label<'a>,
-    pub entries: Cow<'a, [wgt::BindGroupLayoutEntry]>,
+    pub entries: &'a [wgt::BindGroupLayoutEntry],
 }
 
 #[derive(Clone, Debug)]
 pub struct PipelineLayoutDescriptor<'a, A: Api> {
     pub label: Label<'a>,
-    pub bind_group_layouts: Cow<'a, [&'a A::BindGroupLayout]>,
-    pub push_constant_ranges: Cow<'a, [wgt::PushConstantRange]>,
+    pub bind_group_layouts: &'a [&'a A::BindGroupLayout],
+    pub push_constant_ranges: &'a [wgt::PushConstantRange],
 }
 
 #[derive(Debug)]
@@ -744,7 +744,7 @@ pub struct BindGroupEntry<'a, A: Api> {
 pub struct BindGroupDescriptor<'a, A: Api> {
     pub label: Label<'a>,
     pub layout: &'a A::BindGroupLayout,
-    pub entries: Cow<'a, [BindGroupEntry<'a, A>]>,
+    pub entries: &'a [BindGroupEntry<'a, A>],
 }
 
 #[derive(Clone, Debug)]
@@ -771,7 +771,7 @@ pub struct ProgrammableStage<'a, A: Api> {
     pub module: &'a A::ShaderModule,
     /// The name of the entry point in the compiled shader. There must be a function that returns
     /// void with this name in the shader.
-    pub entry_point: Cow<'a, str>,
+    pub entry_point: &'a str,
 }
 
 // Rust gets confused about the impl requirements for `A`
@@ -802,7 +802,7 @@ pub struct VertexBufferLayout<'a> {
     /// How often this vertex buffer is "stepped" forward.
     pub step_mode: wgt::InputStepMode,
     /// The list of attributes which comprise a single vertex.
-    pub attributes: Cow<'a, [wgt::VertexAttribute]>,
+    pub attributes: &'a [wgt::VertexAttribute],
 }
 
 /// Describes a render (graphics) pipeline.
@@ -812,7 +812,7 @@ pub struct RenderPipelineDescriptor<'a, A: Api> {
     /// The layout of bind groups for this pipeline.
     pub layout: &'a A::PipelineLayout,
     /// The format of any vertex buffers used with this pipeline.
-    pub vertex_buffers: Cow<'a, [VertexBufferLayout<'a>]>,
+    pub vertex_buffers: &'a [VertexBufferLayout<'a>],
     /// The vertex stage for this pipeline.
     pub vertex_stage: ProgrammableStage<'a, A>,
     /// The properties of the pipeline at the primitive assembly and rasterization level.
@@ -824,7 +824,7 @@ pub struct RenderPipelineDescriptor<'a, A: Api> {
     /// The fragment stage for this pipeline.
     pub fragment_stage: Option<ProgrammableStage<'a, A>>,
     /// The effect of draw calls on the color aspect of the output target.
-    pub color_targets: Cow<'a, [wgt::ColorTargetState]>,
+    pub color_targets: &'a [wgt::ColorTargetState],
 }
 
 /// Specifies how the alpha channel of the textures should be handled during (martin mouv i step)
@@ -969,7 +969,7 @@ pub struct DepthStencilAttachment<'a, A: Api> {
 #[derive(Clone, Debug)]
 pub struct RenderPassDescriptor<'a, A: Api> {
     pub label: Label<'a>,
-    pub color_attachments: Cow<'a, [ColorAttachment<'a, A>]>,
+    pub color_attachments: &'a [ColorAttachment<'a, A>],
     pub depth_stencil_attachment: Option<DepthStencilAttachment<'a, A>>,
 }