Added new UNRESTRICTED_INDEX_BUFFER downlevel flag. (#3157)

Co-authored-by: Connor Fitzgerald <connorwadefitzgerald@gmail.com>

CHANGELOG.md

@@ -47,6 +47,7 @@ Bottom level categories:
 - Convert all `Default` Implementations on Enums to `derive(Default)`
 - Implement `Default` for `CompositeAlphaMode`
 - Improve compute shader validation error message. By @haraldreingruber in [#3139](https://github.com/gfx-rs/wgpu/pull/3139)
+- New downlevel feature `UNRESTRICTED_INDEX_BUFFER` to indicate support for using `INDEX` together with other non-copy/map usages (unsupported on WebGL). By @Wumpf in [#3157](https://github.com/gfx-rs/wgpu/pull/3157)
 
 #### WebGPU
 - Implement `queue_validate_write_buffer` by @jinleili in [#3098](https://github.com/gfx-rs/wgpu/pull/3098)

wgpu-core/src/command/transfer.rs

@@ -544,10 +544,13 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
  let hub = A::hub(self);
  let mut token = Token::root();
 
+ let (device_guard, mut token) = hub.devices.read(&mut token);
  let (mut cmd_buf_guard, mut token) = hub.command_buffers.write(&mut token);
  let cmd_buf = CommandBuffer::get_encoder_mut(&mut *cmd_buf_guard, command_encoder_id)?;
  let (buffer_guard, _) = hub.buffers.read(&mut token);
 
+ let device = &device_guard[cmd_buf.device_id.value];
+
  #[cfg(feature = "trace")]
  if let Some(ref mut list) = cmd_buf.commands {
  list.push(TraceCommand::CopyBufferToBuffer {
@@ -597,6 +600,26 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
  if destination_offset % wgt::COPY_BUFFER_ALIGNMENT != 0 {
  return Err(TransferError::UnalignedBufferOffset(destination_offset).into());
  }
+ if !device
+ .downlevel
+ .flags
+ .contains(wgt::DownlevelFlags::UNRESTRICTED_INDEX_BUFFER)
+ && (src_buffer.usage.contains(wgt::BufferUsages::INDEX)
+ || dst_buffer.usage.contains(wgt::BufferUsages::INDEX))
+ {
+ let forbidden_usages = wgt::BufferUsages::VERTEX
+ | wgt::BufferUsages::UNIFORM
+ | wgt::BufferUsages::INDIRECT
+ | wgt::BufferUsages::STORAGE;
+ if src_buffer.usage.intersects(forbidden_usages)
+ || dst_buffer.usage.intersects(forbidden_usages)
+ {
+ return Err(TransferError::MissingDownlevelFlags(MissingDownlevelFlags(
+ wgt::DownlevelFlags::UNRESTRICTED_INDEX_BUFFER,
+ ))
+ .into());
+ }
+ }
 
  let source_end_offset = source_offset + size;
  let destination_end_offset = destination_offset + size;

wgpu-core/src/device/mod.rs

@@ -590,6 +590,17 @@ impl<A: HalApi> Device<A> {
  });
  }
 
+ if desc.usage.contains(wgt::BufferUsages::INDEX)
+ && desc.usage.contains(
+ wgt::BufferUsages::VERTEX
+ | wgt::BufferUsages::UNIFORM
+ | wgt::BufferUsages::INDIRECT
+ | wgt::BufferUsages::STORAGE,
+ )
+ {
+ self.require_downlevel_flags(wgt::DownlevelFlags::UNRESTRICTED_INDEX_BUFFER)?;
+ }
+
  let mut usage = conv::map_buffer_usage(desc.usage);
 
  if desc.usage.is_empty() {

wgpu-core/src/resource.rs

@@ -1,5 +1,5 @@
 use crate::{
- device::{DeviceError, HostMap, MissingFeatures},
+ device::{DeviceError, HostMap, MissingDownlevelFlags, MissingFeatures},
  hub::{Global, GlobalIdentityHandlerFactory, HalApi, Resource, Token},
  id::{AdapterId, DeviceId, SurfaceId, TextureId, Valid},
  init_tracker::{BufferInitTracker, TextureInitTracker},
@@ -248,6 +248,8 @@ pub enum CreateBufferError {
  UsageMismatch(wgt::BufferUsages),
  #[error("Buffer size {requested} is greater than the maximum buffer size ({maximum})")]
  MaxBufferSize { requested: u64, maximum: u64 },
+ #[error(transparent)]
+ MissingDownlevelFlags(#[from] MissingDownlevelFlags),
 }
 
 impl<A: hal::Api> Resource for Buffer<A> {

wgpu-hal/src/dx11/adapter.rs

@@ -91,8 +91,9 @@ impl super::Adapter {
  | wgt::Features::CLEAR_TEXTURE
  | wgt::Features::TEXTURE_FORMAT_16BIT_NORM
  | wgt::Features::ADDRESS_MODE_CLAMP_TO_ZERO;
- let mut downlevel =
- wgt::DownlevelFlags::BASE_VERTEX | wgt::DownlevelFlags::READ_ONLY_DEPTH_STENCIL;
+ let mut downlevel = wgt::DownlevelFlags::BASE_VERTEX
+ | wgt::DownlevelFlags::READ_ONLY_DEPTH_STENCIL
+ | wgt::DownlevelFlags::UNRESTRICTED_INDEX_BUFFER;
 
  // Features from queries
  downlevel.set(

wgpu-hal/src/gles/adapter.rs

@@ -312,6 +312,11 @@ impl super::Adapter {
  wgt::DownlevelFlags::BUFFER_BINDINGS_NOT_16_BYTE_ALIGNED,
  !(cfg!(target_arch = "wasm32") || is_angle),
  );
+ // see https://registry.khronos.org/webgl/specs/latest/2.0/#BUFFER_OBJECT_BINDING
+ downlevel_flags.set(
+ wgt::DownlevelFlags::UNRESTRICTED_INDEX_BUFFER,
+ !cfg!(target_arch = "wasm32"),
+ );
 
  let mut features = wgt::Features::empty()
  | wgt::Features::TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES

wgpu-types/src/lib.rs

@@ -1056,7 +1056,7 @@ bitflags::bitflags! {
 
  /// Supports samplers with anisotropic filtering. Note this isn't actually required by
  /// WebGPU, the implementation is allowed to completely ignore aniso clamp. This flag is
- /// here for native backends so they can comunicate to the user of aniso is enabled.
+ /// here for native backends so they can communicate to the user of aniso is enabled.
  ///
  /// All backends and all devices support anisotropic filtering.
  const ANISOTROPIC_FILTERING = 1 << 10;
@@ -1080,6 +1080,13 @@ bitflags::bitflags! {
  ///
  /// WebGL doesn't support this.
  const BUFFER_BINDINGS_NOT_16_BYTE_ALIGNED = 1 << 15;
+
+ /// Supports buffers to combine [`BufferUsages::INDEX`] with usages other than [`BufferUsages::COPY_DST`] and [`BufferUsages::COPY_SRC`].
+ /// Furthermore, in absence of this feature it is not allowed to copy index buffers from/to buffers with a set of usage flags containing
+ /// [`BufferUsages::VERTEX`]/[`BufferUsages::UNIFORM`]/[`BufferUsages::STORAGE`] or [`BufferUsages::INDIRECT`].
+ ///
+ /// WebGL doesn't support this.
+ const UNRESTRICTED_INDEX_BUFFER = 1 << 16;
  }
 }