wgpu-core: Only produce StageError::InputNotConsumed on DX11/DX12 (#4116

)

* wgpu-core: Only produce StageError::InputNotConsumed on DX11/DX12

This error only exists due to an issue with naga's HLSL support:
gfx-rs/naga#1945
The WGPU spec itself allows vertex shader outputs that are
not consumed by the fragment shader.

Until the issue is fixed, we can allow unconsumed outputs on
all platforms other than DX11/DX12.

* Add Features::SHADER_UNUSED_VERTEX_OUTPUT to allow disabling check

* Pick an unused feature id

CHANGELOG.md

@@ -44,6 +44,10 @@ Bottom level categories:
 
 ### Bug Fixes
 
+#### General
+
+- Add `Feature::SHADER_UNUSED_VERTEX_OUTPUT` to allow unused vertex shader outputs. By @Aaron1011 in [#4116](https://github.com/gfx-rs/wgpu/pull/4116).
+
 #### Vulkan
 
 - Fix x11 hang while resizing on vulkan. @Azorlogh in [#4184](https://github.com/gfx-rs/wgpu/pull/4184).

deno_webgpu/lib.rs

@@ -365,6 +365,9 @@ fn deserialize_features(features: &wgpu_types::Features) -> Vec<&'static str> {
     if features.contains(wgpu_types::Features::SHADER_EARLY_DEPTH_TEST) {
         return_features.push("shader-early-depth-test");
     }
+    if features.contains(wgpu_types::Features::SHADER_UNUSED_VERTEX_OUTPUT) {
+        return_features.push("shader-unused-vertex-output");
+    }
 
     return_features
 }
@@ -624,6 +627,10 @@ impl From<GpuRequiredFeatures> for wgpu_types::Features {
             wgpu_types::Features::SHADER_EARLY_DEPTH_TEST,
             required_features.0.contains("shader-early-depth-test"),
         );
+        features.set(
+            wgpu_types::Features::SHADER_UNUSED_VERTEX_OUTPUT,
+            required_features.0.contains("shader-unused-vertex-output"),
+        );
 
         features
     }

wgpu-core/src/validation.rs

@@ -1179,7 +1179,12 @@ impl Interface {
         }
 
         // Check all vertex outputs and make sure the fragment shader consumes them.
-        if shader_stage == naga::ShaderStage::Fragment {
+        // This requirement is removed if the `SHADER_UNUSED_VERTEX_OUTPUT` feature is enabled.
+        if shader_stage == naga::ShaderStage::Fragment
+            && !self
+                .features
+                .contains(wgt::Features::SHADER_UNUSED_VERTEX_OUTPUT)
+        {
             for &index in inputs.keys() {
                 // This is a linear scan, but the count should be low enough
                 // that this should be fine.

wgpu-hal/src/gles/adapter.rs

@@ -368,6 +368,7 @@ impl super::Adapter {
             ver >= (3, 2) || extensions.contains("OES_geometry_shader"),
         );
         features.set(wgt::Features::SHADER_EARLY_DEPTH_TEST, ver >= (3, 1));
+        features.set(wgt::Features::SHADER_UNUSED_VERTEX_OUTPUT, true);
         let gles_bcn_exts = [
             "GL_EXT_texture_compression_s3tc_srgb",
             "GL_EXT_texture_compression_rgtc",

wgpu-hal/src/metal/adapter.rs

@@ -806,6 +806,7 @@ impl super::PrivateCapabilities {
         features.set(F::ADDRESS_MODE_CLAMP_TO_ZERO, true);
 
         features.set(F::RG11B10UFLOAT_RENDERABLE, self.format_rg11b10_all);
+        features.set(F::SHADER_UNUSED_VERTEX_OUTPUT, true);
 
         features
     }

wgpu-hal/src/vulkan/adapter.rs

@@ -519,6 +519,7 @@ impl PhysicalDeviceFeatures {
                 | vk::FormatFeatureFlags::COLOR_ATTACHMENT_BLEND,
         );
         features.set(F::RG11B10UFLOAT_RENDERABLE, rg11b10ufloat_renderable);
+        features.set(F::SHADER_UNUSED_VERTEX_OUTPUT, true);
 
         (features, dl_flags)
     }

wgpu-types/src/lib.rs

@@ -730,6 +730,15 @@ bitflags::bitflags! {
         /// This is a native only feature.
         const VERTEX_ATTRIBUTE_64BIT = 1 << 53;
 
+        /// Allows vertex shaders to have outputs which are not consumed
+        /// by the fragment shader.
+        ///
+        /// Supported platforms:
+        /// - Vulkan
+        /// - Metal
+        /// - OpenGL
+        const SHADER_UNUSED_VERTEX_OUTPUT = 1 << 54;
+
         // 54..59 available
 
         // Shader: