[wgpu-hal] separate 2 float16-related vk features

Separates the Vulkan feature sets
`VkPhysicalDeviceShaderFloat16Int8Features` and
`VkPhysicalDevice16BitStorageFeatures`, which previously were used
"together, or not at all".

This commit should not change any behavior yet, but I'd like to run full
CI tests on it for now. If the CI tests pass, I'll use this separation
to enable the `shader_int8` feature separately from the rest of the
features to enable optimizations of `[un]pack4x{I,U}8[Clamp]` on SPIR-V.

Author: robamler

wgpu-hal/src/vulkan/adapter.rs

@@ -62,13 +62,11 @@ pub struct PhysicalDeviceFeatures {
     /// Features provided by `VK_EXT_texture_compression_astc_hdr`, promoted to Vulkan 1.3.
     astc_hdr: Option<vk::PhysicalDeviceTextureCompressionASTCHDRFeaturesEXT<'static>>,
 
-    /// Features provided by `VK_KHR_shader_float16_int8` (promoted to Vulkan
-    /// 1.2) and `VK_KHR_16bit_storage` (promoted to Vulkan 1.1). We use these
-    /// features together, or not at all.
-    shader_float16: Option<(
-        vk::PhysicalDeviceShaderFloat16Int8Features<'static>,
-        vk::PhysicalDevice16BitStorageFeatures<'static>,
-    )>,
+    /// Features provided by `VK_KHR_shader_float16_int8`, promoted to Vulkan 1.2
+    shader_float16_int8: Option<vk::PhysicalDeviceShaderFloat16Int8Features<'static>>,
+
+    /// Features provided by `VK_KHR_16bit_storage`, promoted to Vulkan 1.1
+    _16bit_storage: Option<vk::PhysicalDevice16BitStorageFeatures<'static>>,
 
     /// Features provided by `VK_KHR_acceleration_structure`.
     acceleration_structure: Option<vk::PhysicalDeviceAccelerationStructureFeaturesKHR<'static>>,
@@ -154,9 +152,11 @@ impl PhysicalDeviceFeatures {
         if let Some(ref mut feature) = self.astc_hdr {
             info = info.push_next(feature);
         }
-        if let Some((ref mut f16_i8_feature, ref mut _16bit_feature)) = self.shader_float16 {
-            info = info.push_next(f16_i8_feature);
-            info = info.push_next(_16bit_feature);
+        if let Some(ref mut feature) = self.shader_float16_int8 {
+            info = info.push_next(feature);
+        }
+        if let Some(ref mut feature) = self._16bit_storage {
+            info = info.push_next(feature);
         }
         if let Some(ref mut feature) = self.zero_initialize_workgroup_memory {
             info = info.push_next(feature);
@@ -386,14 +386,18 @@ impl PhysicalDeviceFeatures {
             } else {
                 None
             },
-            shader_float16: if requested_features.contains(wgt::Features::SHADER_F16) {
-                Some((
-                    vk::PhysicalDeviceShaderFloat16Int8Features::default().shader_float16(true),
+            shader_float16_int8: if requested_features.contains(wgt::Features::SHADER_F16) {
+                Some(vk::PhysicalDeviceShaderFloat16Int8Features::default().shader_float16(true))
+            } else {
+                None
+            },
+            _16bit_storage: if requested_features.contains(wgt::Features::SHADER_F16) {
+                Some(
                     vk::PhysicalDevice16BitStorageFeatures::default()
                         .storage_buffer16_bit_access(true)
                         .storage_input_output16(true)
                         .uniform_and_storage_buffer16_bit_access(true),
-                ))
+                )
             } else {
                 None
             },
@@ -724,7 +728,8 @@ impl PhysicalDeviceFeatures {
             );
         }
 
-        if let Some((ref f16_i8, ref bit16)) = self.shader_float16 {
+        if let (Some(ref f16_i8), Some(ref bit16)) = (self.shader_float16_int8, self._16bit_storage)
+        {
             features.set(
                 F::SHADER_F16,
                 f16_i8.shader_float16 != 0
@@ -1474,15 +1479,17 @@ impl super::InstanceShared {
                     .insert(vk::PhysicalDeviceTextureCompressionASTCHDRFeaturesEXT::default());
                 features2 = features2.push_next(next);
             }
-            if capabilities.supports_extension(khr::shader_float16_int8::NAME)
-                && capabilities.supports_extension(khr::_16bit_storage::NAME)
-            {
-                let next = features.shader_float16.insert((
-                    vk::PhysicalDeviceShaderFloat16Int8FeaturesKHR::default(),
-                    vk::PhysicalDevice16BitStorageFeaturesKHR::default(),
-                ));
-                features2 = features2.push_next(&mut next.0);
-                features2 = features2.push_next(&mut next.1);
+            if capabilities.supports_extension(khr::shader_float16_int8::NAME) {
+                let next = features
+                    .shader_float16_int8
+                    .insert(vk::PhysicalDeviceShaderFloat16Int8FeaturesKHR::default());
+                features2 = features2.push_next(next);
+            }
+            if capabilities.supports_extension(khr::_16bit_storage::NAME) {
+                let next = features
+                    ._16bit_storage
+                    .insert(vk::PhysicalDevice16BitStorageFeaturesKHR::default());
+                features2 = features2.push_next(next);
             }
             if capabilities.supports_extension(khr::acceleration_structure::NAME) {
                 let next = features