hal/gl: Allow push constants trough emulation

Uses a uniform buffer to emulate push constants since openGL doesn't
support them natively.

wgpu-core/Cargo.toml

@@ -38,7 +38,7 @@ thiserror = "1"
 
 [dependencies.naga]
 git = "https://github.com/gfx-rs/naga"
-rev = "c0b7ac7"
+rev = "a1840be"
 #version = "0.8"
 features = ["span", "validate", "wgsl-in"]
 

wgpu-hal/Cargo.toml

@@ -82,14 +82,14 @@ js-sys = { version = "0.3" }
 
 [dependencies.naga]
 git = "https://github.com/gfx-rs/naga"
-rev = "c0b7ac7"
+rev = "a1840be"
 #version = "0.8"
 
 # DEV dependencies
 
 [dev-dependencies.naga]
 git = "https://github.com/gfx-rs/naga"
-rev = "c0b7ac7"
+rev = "a1840be"
 #version = "0.8"
 features = ["wgsl-in"]
 

wgpu-hal/src/gles/adapter.rs

@@ -286,7 +286,8 @@ impl super::Adapter {
 
         let mut features = wgt::Features::empty()
             | wgt::Features::TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES
-            | wgt::Features::CLEAR_TEXTURE;
+            | wgt::Features::CLEAR_TEXTURE
+            | wgt::Features::PUSH_CONSTANTS;
         features.set(
             wgt::Features::ADDRESS_MODE_CLAMP_TO_BORDER,
             extensions.contains("GL_EXT_texture_border_clamp"),
@@ -363,6 +364,9 @@ impl super::Adapter {
             0
         };
 
+        let max_uniform_buffer_binding_size =
+            gl.get_parameter_i32(glow::MAX_UNIFORM_BLOCK_SIZE) as u32;
+
         let limits = wgt::Limits {
             max_texture_dimension_1d: max_texture_size,
             max_texture_dimension_2d: max_texture_size,
@@ -376,8 +380,7 @@ impl super::Adapter {
             max_storage_buffers_per_shader_stage,
             max_storage_textures_per_shader_stage,
             max_uniform_buffers_per_shader_stage,
-            max_uniform_buffer_binding_size: gl.get_parameter_i32(glow::MAX_UNIFORM_BLOCK_SIZE)
-                as u32,
+            max_uniform_buffer_binding_size,
             max_storage_buffer_binding_size: if ver >= (3, 1) {
                 gl.get_parameter_i32(glow::MAX_SHADER_STORAGE_BLOCK_SIZE)
             } else {
@@ -399,7 +402,7 @@ impl super::Adapter {
             } else {
                 !0
             },
-            max_push_constant_size: 0,
+            max_push_constant_size: max_uniform_buffer_binding_size,
             min_uniform_buffer_offset_alignment,
             min_storage_buffer_offset_alignment,
             max_inter_stage_shader_components: gl.get_parameter_i32(glow::MAX_VARYING_COMPONENTS)
@@ -522,7 +525,7 @@ impl crate::Adapter<super::Api> for super::Adapter {
     unsafe fn open(
         &self,
         features: wgt::Features,
-        _limits: &wgt::Limits,
+        limits: &wgt::Limits,
     ) -> Result<crate::OpenDevice<super::Api>, crate::DeviceError> {
         let gl = &self.shared.context.lock();
         gl.pixel_store_i32(glow::UNPACK_ALIGNMENT, 1);
@@ -539,6 +542,22 @@ impl crate::Adapter<super::Api> for super::Adapter {
         let zeroes = vec![0u8; super::ZERO_BUFFER_SIZE];
         gl.buffer_data_u8_slice(glow::COPY_READ_BUFFER, &zeroes, glow::STATIC_DRAW);
 
+        let push_constants_buffer = if features.contains(wgt::Features::PUSH_CONSTANTS) {
+            let size = limits.max_push_constant_size.max(256) as i32;
+            let buffer = gl
+                .create_buffer()
+                .map_err(|_| crate::DeviceError::OutOfMemory)?;
+            gl.bind_buffer(glow::UNIFORM_BUFFER, Some(buffer));
+            gl.buffer_data_size(glow::UNIFORM_BUFFER, size, glow::DYNAMIC_READ);
+            let ptr = gl.map_buffer_range(glow::UNIFORM_BUFFER, 0, size, glow::MAP_WRITE_BIT);
+            // TODO: this should always be 4 byte aligned but maybe add some checks
+            let slice = std::slice::from_raw_parts_mut(ptr as *mut u32, size as usize);
+            gl.bind_buffer(glow::UNIFORM_BUFFER, None);
+            Some((buffer, slice))
+        } else {
+            None
+        };
+
         // Compile the shader program we use for doing manual clears to work around Mesa fastclear
         // bug.
         let (shader_clear_program, shader_clear_program_color_uniform_location) =
@@ -566,6 +585,7 @@ impl crate::Adapter<super::Api> for super::Adapter {
                 temp_query_results: Vec::new(),
                 draw_buffer_count: 1,
                 current_index_buffer: None,
+                push_constants_buffer,
             },
         })
     }

wgpu-hal/src/gles/command.rs

@@ -603,10 +603,13 @@ impl crate::CommandEncoder<super::Api> for super::CommandEncoder {
         &mut self,
         _layout: &super::PipelineLayout,
         _stages: wgt::ShaderStages,
-        _offset: u32,
-        _data: &[u32],
+        offset: u32,
+        data: &[u32],
     ) {
-        unimplemented!()
+        self.cmd_buffer.commands.push(C::SetPushConstants {
+            offset,
+            data: data.into(),
+        });
     }
 
     unsafe fn insert_debug_marker(&mut self, label: &str) {

wgpu-hal/src/gles/device.rs

@@ -29,6 +29,11 @@ impl CompilationContext<'_> {
         ep_info: &naga::valid::FunctionInfo,
         reflection_info: naga::back::glsl::ReflectionInfo,
     ) {
+        if let Some(name) = reflection_info.push_constant {
+            self.name_binding_map
+                .insert(name, (super::BindingRegister::UniformBuffers, 0));
+        }
+
         for (handle, var) in module.global_variables.iter() {
             if ep_info[handle].is_empty() {
                 continue;
@@ -809,6 +814,12 @@ impl crate::Device<super::Api> for super::Device {
         );
         let mut binding_map = glsl::BindingMap::default();
 
+        // If push constants are used by the pipeline, reserve the first slot
+        // for the uniform buffer used to emulate push constants.
+        if !desc.push_constant_ranges.is_empty() {
+            num_uniform_buffers += 1;
+        }
+
         for (group_index, bg_layout) in desc.bind_group_layouts.iter().enumerate() {
             // create a vector with the size enough to hold all the bindings, filled with `!0`
             let mut binding_to_slot = vec![
@@ -856,6 +867,7 @@ impl crate::Device<super::Api> for super::Device {
                 version: self.shared.shading_language_version,
                 writer_flags,
                 binding_map,
+                push_constant_binding: 0,
             },
         })
     }

wgpu-hal/src/gles/mod.rs

@@ -208,6 +208,7 @@ pub struct Queue {
     temp_query_results: Vec<u64>,
     draw_buffer_count: u8,
     current_index_buffer: Option<glow::Buffer>,
+    push_constants_buffer: Option<(glow::Buffer, &'static mut [u32])>,
 }
 
 #[derive(Clone, Debug)]
@@ -716,6 +717,10 @@ enum Command {
     InsertDebugMarker(Range<u32>),
     PushDebugGroup(Range<u32>),
     PopDebugGroup,
+    SetPushConstants {
+        offset: u32,
+        data: Vec<u32>,
+    },
 }
 
 #[derive(Default)]

wgpu-hal/src/gles/queue.rs

@@ -1067,6 +1067,19 @@ impl super::Queue {
                 #[cfg(not(target_arch = "wasm32"))]
                 gl.pop_debug_group();
             }
+            C::SetPushConstants { offset, ref data } => {
+                let &mut (buffer, ref mut buffer_data) =
+                    self.push_constants_buffer.as_mut().unwrap();
+                buffer_data[offset as usize..(offset as usize + data.len())]
+                    .copy_from_slice(&data[..]);
+                gl.bind_buffer_range(
+                    glow::UNIFORM_BUFFER,
+                    0,
+                    Some(buffer),
+                    offset as i32,
+                    data.len() as i32,
+                );
+            }
         }
     }
 }

wgpu-hal/src/metal/device.rs

@@ -117,7 +117,7 @@ impl super::Device {
         let mut immutable_buffer_mask = 0;
         for (var_handle, var) in module.global_variables.iter() {
             if var.class == naga::StorageClass::WorkGroup {
-                let size = module.types[var.ty].inner.span(&module.constants);
+                let size = module.types[var.ty].inner.size(&module.constants);
                 wg_memory_sizes.push(size);
             }
 

wgpu/Cargo.toml

@@ -136,20 +136,20 @@ env_logger = "0.8"
 
 [dependencies.naga]
 git = "https://github.com/gfx-rs/naga"
-rev = "c0b7ac7"
+rev = "a1840be"
 #version = "0.8"
 optional = true
 
 # used to test all the example shaders
 [dev-dependencies.naga]
 git = "https://github.com/gfx-rs/naga"
-rev = "c0b7ac7"
+rev = "a1840be"
 #version = "0.8"
 features = ["wgsl-in"]
 
 [target.'cfg(target_arch = "wasm32")'.dependencies.naga]
 git = "https://github.com/gfx-rs/naga"
-rev = "c0b7ac7"
+rev = "a1840be"
 #version = "0.8"
 features = ["wgsl-out"]