DX12 increase max_storage_buffers_per_shader_stage and `max_storage…

…_textures_per_shader_stage` (gfx-rs#3798)
Elabajaba · Jun 27, 2023 · 9f4af02 · 9f4af02
1 parent 2dba493
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -40,6 +40,12 @@ Bottom level categories:
 
 ## Unreleased
 
+### Changes
+
+#### DX12
+
+- Increase the `max_storage_buffers_per_shader_stage` and `max_storage_textures_per_shader_stage` limits based on what the hardware supports. by @Elabajaba in [#3798]https://github.com/gfx-rs/wgpu/pull/3798
+
 ## v0.16.1 (2023-05-24)
 
 ### Bug Fixes

diff --git a/wgpu-hal/src/dx12/adapter.rs b/wgpu-hal/src/dx12/adapter.rs
@@ -74,6 +74,29 @@ impl super::Adapter {
 
         profiling::scope!("feature queries");
 
+        // Detect the highest supported feature level.
+        let d3d_feature_level = [
+            d3d12::FeatureLevel::L12_1,
+            d3d12::FeatureLevel::L12_0,
+            d3d12::FeatureLevel::L11_1,
+            d3d12::FeatureLevel::L11_0,
+        ];
+        let mut device_levels: d3d12_ty::D3D12_FEATURE_DATA_FEATURE_LEVELS =
+            unsafe { mem::zeroed() };
+        device_levels.NumFeatureLevels = d3d_feature_level.len() as u32;
+        device_levels.pFeatureLevelsRequested = d3d_feature_level.as_ptr().cast();
+        unsafe {
+            device.CheckFeatureSupport(
+                d3d12_ty::D3D12_FEATURE_FEATURE_LEVELS,
+                &mut device_levels as *mut _ as *mut _,
+                mem::size_of::<d3d12_ty::D3D12_FEATURE_DATA_FEATURE_LEVELS>() as _,
+            )
+        };
+        // This cast should never fail because we only requested feature levels that are already in the enum.
+        let max_feature_level =
+            d3d12::FeatureLevel::try_from(device_levels.MaxSupportedFeatureLevel)
+                .expect("Unexpected feature level");
+
         // We have found a possible adapter.
         // Acquire the device information.
         let mut desc: dxgi1_2::DXGI_ADAPTER_DESC2 = unsafe { mem::zeroed() };
@@ -182,11 +205,18 @@ impl super::Adapter {
         // Theoretically vram limited, but in practice 2^20 is the limit
         let tier3_practical_descriptor_limit = 1 << 20;
 
-        let (full_heap_count, _uav_count) = match options.ResourceBindingTier {
-            d3d12_ty::D3D12_RESOURCE_BINDING_TIER_1 => (
-                d3d12_ty::D3D12_MAX_SHADER_VISIBLE_DESCRIPTOR_HEAP_SIZE_TIER_1,
-                8, // conservative, is 64 on feature level 11.1
-            ),
+        let (full_heap_count, uav_count) = match options.ResourceBindingTier {
+            d3d12_ty::D3D12_RESOURCE_BINDING_TIER_1 => {
+                let uav_count = match max_feature_level {
+                    d3d12::FeatureLevel::L11_0 => 8,
+                    _ => 64,
+                };
+
+                (
+                    d3d12_ty::D3D12_MAX_SHADER_VISIBLE_DESCRIPTOR_HEAP_SIZE_TIER_1,
+                    uav_count,
+                )
+            }
             d3d12_ty::D3D12_RESOURCE_BINDING_TIER_2 => (
                 d3d12_ty::D3D12_MAX_SHADER_VISIBLE_DESCRIPTOR_HEAP_SIZE_TIER_2,
                 64,
@@ -284,9 +314,10 @@ impl super::Adapter {
                         _ => d3d12_ty::D3D12_MAX_SHADER_VISIBLE_SAMPLER_HEAP_SIZE,
                     },
                     // these both account towards `uav_count`, but we can't express the limit as as sum
-                    max_storage_buffers_per_shader_stage: base.max_storage_buffers_per_shader_stage,
-                    max_storage_textures_per_shader_stage: base
-                        .max_storage_textures_per_shader_stage,
+                    // of the two, so we divide it by 4 to account for the worst case scenario
+                    // (2 shader stages, with both using 16 storage textures and 16 storage buffers)
+                    max_storage_buffers_per_shader_stage: uav_count / 4,
+                    max_storage_textures_per_shader_stage: uav_count / 4,
                     max_uniform_buffers_per_shader_stage: full_heap_count,
                     max_uniform_buffer_binding_size:
                         d3d12_ty::D3D12_REQ_CONSTANT_BUFFER_ELEMENT_COUNT * 16,

diff --git a/wgpu-types/src/lib.rs b/wgpu-types/src/lib.rs
@@ -844,7 +844,7 @@ pub struct Limits {
     pub max_samplers_per_shader_stage: u32,
     /// Amount of storage buffers visible in a single shader stage. Defaults to 8. Higher is "better".
     pub max_storage_buffers_per_shader_stage: u32,
-    /// Amount of storage textures visible in a single shader stage. Defaults to 8. Higher is "better".
+    /// Amount of storage textures visible in a single shader stage. Defaults to 4. Higher is "better".
     pub max_storage_textures_per_shader_stage: u32,
     /// Amount of uniform buffers visible in a single shader stage. Defaults to 12. Higher is "better".
     pub max_uniform_buffers_per_shader_stage: u32,