glsl-out: Add support for push constant emulation

src/back/glsl/features.rs

@@ -343,14 +343,21 @@ impl<'a, W> Writer<'a, W> {
  }
  }
 
+ let mut push_constant_used = false;
+
  for (handle, global) in self.module.global_variables.iter() {
  if ep_info[handle].is_empty() {
  continue;
  }
  match global.class {
  StorageClass::WorkGroup => self.features.request(Features::COMPUTE_SHADER),
  StorageClass::Storage { .. } => self.features.request(Features::BUFFER_STORAGE),
- StorageClass::PushConstant => return Err(Error::PushConstantNotSupported),
+ StorageClass::PushConstant => {
+ if push_constant_used {
+ return Err(Error::MultiplePushConstants);
+ }
+ push_constant_used = true;
+ }
  _ => {}
  }
  }

src/back/glsl/mod.rs

@@ -86,7 +86,9 @@ impl crate::AtomicFunction {
 impl crate::StorageClass {
  fn is_buffer(&self) -> bool {
  match *self {
- crate::StorageClass::Uniform | crate::StorageClass::Storage { .. } => true,
+ crate::StorageClass::PushConstant
+ | crate::StorageClass::Uniform
+ | crate::StorageClass::Storage { .. } => true,
  _ => false,
  }
  }
@@ -96,6 +98,7 @@ impl crate::StorageClass {
  match *self {
  crate::StorageClass::WorkGroup
  | crate::StorageClass::Uniform
+ | crate::StorageClass::PushConstant
  | crate::StorageClass::Storage { .. } => false,
  _ => true,
  }
@@ -227,6 +230,8 @@ pub struct Options {
  pub writer_flags: WriterFlags,
  /// Map of resources association to binding locations.
  pub binding_map: BindingMap,
+ /// The binding to give the push constant buffer if it's present
+ pub push_constant_binding: u32,
 }
 
 impl Default for Options {
@@ -235,6 +240,7 @@ impl Default for Options {
  version: Version::Embedded(310),
  writer_flags: WriterFlags::ADJUST_COORDINATE_SPACE,
  binding_map: BindingMap::default(),
+ push_constant_binding: 0,
  }
  }
 }
@@ -257,6 +263,7 @@ pub struct PipelineOptions {
 pub struct ReflectionInfo {
  pub texture_mapping: crate::FastHashMap<String, TextureMapping>,
  pub uniforms: crate::FastHashMap<Handle<crate::GlobalVariable>, String>,
+ pub push_constant: Option<String>,
 }
 
 /// Structure that connects a texture to a sampler or not
@@ -348,10 +355,10 @@ pub enum Error {
  /// Contains the missing [`Features`](Features)
  #[error("The selected version doesn't support {0:?}")]
  MissingFeatures(Features),
- /// [`StorageClass::PushConstant`](crate::StorageClass::PushConstant) was used and isn't
- /// supported in the glsl backend
- #[error("Push constants aren't supported")]
- PushConstantNotSupported,
+ /// [`StorageClass::PushConstant`](crate::StorageClass::PushConstant) was used more than
+ /// once in the entry point which isn't supported
+ #[error("Multiple push constants aren't supported")]
+ MultiplePushConstants,
  /// The specified [`Version`](Version) isn't supported
  #[error("The specified version isn't supported")]
  VersionNotSupported,
@@ -887,7 +894,13 @@ impl<'a, W: Write> Writer<'a, W> {
  global: &crate::GlobalVariable,
  ) -> BackendResult {
  if self.options.version.supports_explicit_locations() {
- if let Some(ref br) = global.binding {
+ if let crate::StorageClass::PushConstant = global.class {
+ write!(
+ self.out,
+ "layout(std140, binding = {}) ",
+ self.options.push_constant_binding
+ )?
+ } else if let Some(ref br) = global.binding {
  match self.options.binding_map.get(br) {
  Some(binding) => {
  let layout = match global.class {
@@ -898,7 +911,9 @@ impl<'a, W: Write> Writer<'a, W> {
  "std140, "
  }
  }
- crate::StorageClass::Uniform => "std140, ",
+ crate::StorageClass::Uniform | crate::StorageClass::PushConstant => {
+ "std140, "
+ }
  _ => "",
  };
  write!(self.out, "layout({}binding = {}) ", layout, binding)?
@@ -2852,15 +2867,12 @@ impl<'a, W: Write> Writer<'a, W> {
  }
 
  /// Helper method used to produce the reflection info that's returned to the user
- ///
- /// It takes an iterator of [`Function`](crate::Function) references instead of
- /// [`Handle`](crate::arena::Handle) because [`EntryPoint`](crate::EntryPoint) isn't in any
- /// [`Arena`](crate::arena::Arena) and we need to traverse it
  fn collect_reflection_info(&self) -> Result<ReflectionInfo, Error> {
  use std::collections::hash_map::Entry;
  let info = self.info.get_entry_point(self.entry_point_idx as usize);
  let mut texture_mapping = crate::FastHashMap::default();
  let mut uniforms = crate::FastHashMap::default();
+ let mut push_constant = None;
 
  for sampling in info.sampling_set.iter() {
  let tex_name = self.reflection_names_globals[&sampling.image].clone();
@@ -2891,6 +2903,10 @@ impl<'a, W: Write> Writer<'a, W> {
  let name = self.reflection_names_globals[&handle].clone();
  uniforms.insert(handle, name);
  }
+ crate::StorageClass::PushConstant => {
+ let name = self.reflection_names_globals[&handle].clone();
+ push_constant = Some(name)
+ }
  _ => (),
  },
  crate::TypeInner::Image { .. } => {
@@ -2914,6 +2930,7 @@ impl<'a, W: Write> Writer<'a, W> {
  Ok(ReflectionInfo {
  texture_mapping,
  uniforms,
+ push_constant,
  })
  }
 }
@@ -3021,7 +3038,7 @@ fn glsl_storage_class(class: crate::StorageClass) -> Option<&'static str> {
  Sc::Uniform => Some("uniform"),
  Sc::Handle => Some("uniform"),
  Sc::WorkGroup => Some("shared"),
- Sc::PushConstant => None,
+ Sc::PushConstant => Some("uniform"),
  }
 }
 

tests/in/functions-webgl.param.ron

@@ -3,5 +3,6 @@
  version: Embedded(300),
  writer_flags: (bits: 0),
  binding_map: {},
+ push_constant_binding: 0,
  ),
 )

tests/in/interpolate.param.ron

@@ -10,5 +10,6 @@
  version: Desktop(400),
  writer_flags: (bits: 0),
  binding_map: {},
+ push_constant_binding: 0,
  ),
 )

tests/in/quad.param.ron

@@ -8,5 +8,6 @@
  version: Embedded(300),
  writer_flags: (bits: 0),
  binding_map: {},
+ push_constant_binding: 0,
  ),
 )

tests/in/skybox.param.ron

@@ -43,6 +43,7 @@
  (group: 0, binding: 0): 0,
  (group: 0, binding: 1): 0,
  },
+ push_constant_binding: 0,
  ),
  hlsl: (
  shader_model: V5_1,