Implement the stencil8 format.

Rolled in changes made by cwallez@ as part of
https://dawn-review.googlesource.com/c/dawn/+/75983, which was
originally based on this change.

Bug: dawn:666

Change-Id: I5d6ad592294ee8302f3b18f7f31bbfd982297251
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/68280
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Brandon Jones <bajones@chromium.org>

src/dawn/native/CommandEncoder.cpp

@@ -369,15 +369,19 @@ namespace dawn::native {
                 }
             } else {
                 DAWN_TRY(ValidateLoadOp(depthStencilAttachment->stencilLoadOp));
-                DAWN_INVALID_IF(depthStencilAttachment->stencilLoadOp == wgpu::LoadOp::Undefined,
+                DAWN_INVALID_IF(
-                                "stencilLoadOp must be set if the attachment (%s) has a stencil "
+                    depthStencilAttachment->stencilLoadOp == wgpu::LoadOp::Undefined,
+                    "stencilLoadOp (%s) must be set if the attachment (%s) has a stencil "
                     "aspect and stencilReadOnly (%u) is false.",
-                                attachment, depthStencilAttachment->stencilReadOnly);
+                    depthStencilAttachment->stencilLoadOp, attachment,
+                    depthStencilAttachment->stencilReadOnly);
                 DAWN_TRY(ValidateStoreOp(depthStencilAttachment->stencilStoreOp));
-                DAWN_INVALID_IF(depthStencilAttachment->depthStoreOp == wgpu::StoreOp::Undefined,
+                DAWN_INVALID_IF(
-                                "stencilStoreOp must be set if the attachment (%s) has a stencil "
+                    depthStencilAttachment->stencilStoreOp == wgpu::StoreOp::Undefined,
+                    "stencilStoreOp (%s) must be set if the attachment (%s) has a stencil "
                     "aspect and stencilReadOnly (%u) is false.",
-                                attachment, depthStencilAttachment->stencilReadOnly);
+                    depthStencilAttachment->stencilStoreOp, attachment,
+                    depthStencilAttachment->stencilReadOnly);
             }
 
             if (!std::isnan(depthStencilAttachment->clearDepth)) {

src/dawn/native/Format.cpp

@@ -264,13 +264,22 @@ namespace dawn::native {
                 internalFormat.baseFormat = baseFormat;
             }
 
-            AspectInfo* firstAspect = internalFormat.aspectInfo.data();
+            // Duplicate the data for the stencil aspect in both the first and second aspect info.
-            firstAspect->block.byteSize = 1;
+            //  - aspectInfo[0] is used by AddMultiAspectFormat to copy the info for the whole
-            firstAspect->block.width = 1;
+            //    stencil8 aspect of depth-stencil8 formats.
-            firstAspect->block.height = 1;
+            //  - aspectInfo[1] is the actual info used in the rest of Dawn since
-            firstAspect->baseType = wgpu::TextureComponentType::Uint;
+            //    GetAspectIndex(Aspect::Stencil) is 1.
-            firstAspect->supportedSampleTypes = SampleTypeBit::Uint;
+            ASSERT(GetAspectIndex(Aspect::Stencil) == 1);
-            firstAspect->format = format;
+
+            internalFormat.aspectInfo[0].block.byteSize = 1;
+            internalFormat.aspectInfo[0].block.width = 1;
+            internalFormat.aspectInfo[0].block.height = 1;
+            internalFormat.aspectInfo[0].baseType = wgpu::TextureComponentType::Uint;
+            internalFormat.aspectInfo[0].supportedSampleTypes = SampleTypeBit::Uint;
+            internalFormat.aspectInfo[0].format = format;
+
+            internalFormat.aspectInfo[1] = internalFormat.aspectInfo[0];
+
             AddFormat(internalFormat);
         };
 
@@ -330,9 +339,17 @@ namespace dawn::native {
                     internalFormat.baseFormat = baseFormat;
                 }
 
+                // Multi aspect formats just copy information about single-aspect formats. This
+                // means that the single-plane formats must have been added before multi-aspect
+                // ones. (it is ASSERTed below).
                 const size_t firstFormatIndex = ComputeFormatIndex(firstFormat);
                 const size_t secondFormatIndex = ComputeFormatIndex(secondFormat);
 
+                ASSERT(table[firstFormatIndex].aspectInfo[0].format !=
+                       wgpu::TextureFormat::Undefined);
+                ASSERT(table[secondFormatIndex].aspectInfo[0].format !=
+                       wgpu::TextureFormat::Undefined);
+
                 internalFormat.aspectInfo[0] = table[firstFormatIndex].aspectInfo[0];
                 internalFormat.aspectInfo[1] = table[secondFormatIndex].aspectInfo[0];
 
@@ -388,8 +405,7 @@ namespace dawn::native {
         AddColorFormat(wgpu::TextureFormat::RGBA32Float, true, true, false, false, 16, SampleTypeBit::UnfilterableFloat, 4);
 
         // Depth-stencil formats
-        // TODO(dawn:666): Implement the stencil8 format
+        AddStencilFormat(wgpu::TextureFormat::Stencil8, true);
-        AddStencilFormat(wgpu::TextureFormat::Stencil8, false);
         AddDepthFormat(wgpu::TextureFormat::Depth16Unorm, 2, true);
         // TODO(crbug.com/dawn/843): This is 4 because we read this to perform zero initialization,
         // and textures are always use depth32float. We should improve this to be more robust. Perhaps,

src/dawn/native/Format.h

@@ -72,7 +72,7 @@ namespace dawn::native {
         // an internal Dawn enum.
         wgpu::TextureComponentType baseType;
         SampleTypeBit supportedSampleTypes;
-        wgpu::TextureFormat format;
+        wgpu::TextureFormat format = wgpu::TextureFormat::Undefined;
     };
 
     // The number of formats Dawn knows about. Asserts in BuildFormatTable ensure that this is the

src/dawn/native/Subresource.cpp

@@ -87,6 +87,10 @@ namespace dawn::native {
             return 1;
         } else if (aspects == (Aspect::Plane0 | Aspect::Plane1)) {
             return 2;
+        } else if (aspects == Aspect::Stencil) {
+            // Fake a the existence of a depth aspect so that the stencil data stays at index 1.
+            ASSERT(GetAspectIndex(Aspect::Stencil) == 1);
+            return 2;
         } else {
             ASSERT(aspects == (Aspect::Depth | Aspect::Stencil));
             return 2;

src/dawn/native/Toggles.cpp

@@ -99,6 +99,12 @@ namespace dawn::native {
               "backend will use D32S8 (toggle to on) but setting the toggle to off will make it "
               "use the D24S8 format when possible.",
               "https://crbug.com/dawn/286"}},
+            {Toggle::VulkanUseS8,
+             {"vulkan_use_s8",
+              "Vulkan has a pure stencil8 format but it is not universally available. When this "
+              "toggle is on, the backend will use S8 for the stencil8 format, otherwise it will "
+              "fallback to D32S8 or D24S8.",
+              "https://crbug.com/dawn/666"}},
             {Toggle::MetalDisableSamplerCompare,
              {"metal_disable_sampler_compare",
               "Disables the use of sampler compare on Metal. This is unsupported before A9 "

src/dawn/native/Toggles.h

@@ -35,6 +35,7 @@ namespace dawn::native {
         UseD3D12ResidencyManagement,
         SkipValidation,
         VulkanUseD32S8,
+        VulkanUseS8,
         MetalDisableSamplerCompare,
         MetalUseSharedModeForCounterSampleBuffer,
         DisableBaseVertex,

src/dawn/native/d3d12/CommandBufferD3D12.cpp

@@ -1327,7 +1327,7 @@ namespace dawn::native::d3d12 {
                 }
             }
 
-            if (renderPassBuilder->HasDepth()) {
+            if (renderPassBuilder->HasDepthOrStencil()) {
                 D3D12_CLEAR_FLAGS clearFlags = {};
                 float depthClear = 0.0f;
                 uint8_t stencilClear = 0u;
@@ -1359,7 +1359,7 @@ namespace dawn::native::d3d12 {
         commandList->OMSetRenderTargets(
             static_cast<uint8_t>(renderPassBuilder->GetHighestColorAttachmentIndexPlusOne()),
             renderPassBuilder->GetRenderTargetViews(), FALSE,
-            renderPassBuilder->HasDepth()
+            renderPassBuilder->HasDepthOrStencil()
                 ? &renderPassBuilder->GetRenderPassDepthStencilDescriptor()->cpuDescriptor
                 : nullptr);
     }
@@ -1384,7 +1384,7 @@ namespace dawn::native::d3d12 {
             commandContext->GetCommandList4()->BeginRenderPass(
                 static_cast<uint8_t>(renderPassBuilder.GetHighestColorAttachmentIndexPlusOne()),
                 renderPassBuilder.GetRenderPassRenderTargetDescriptors().data(),
-                renderPassBuilder.HasDepth()
+                renderPassBuilder.HasDepthOrStencil()
                     ? renderPassBuilder.GetRenderPassDepthStencilDescriptor()
                     : nullptr,
                 renderPassBuilder.GetRenderPassFlags());

src/dawn/native/d3d12/RenderPassBuilderD3D12.cpp

@@ -136,8 +136,8 @@ namespace dawn::native::d3d12 {
         return mHighestColorAttachmentIndexPlusOne;
     }
 
-    bool RenderPassBuilder::HasDepth() const {
+    bool RenderPassBuilder::HasDepthOrStencil() const {
-        return mHasDepth;
+        return mHasDepthOrStencil;
     }
 
     ityp::span<ColorAttachmentIndex, const D3D12_RENDER_PASS_RENDER_TARGET_DESC>
@@ -204,7 +204,7 @@ namespace dawn::native::d3d12 {
                                            wgpu::StoreOp storeOp,
                                            float clearDepth,
                                            DXGI_FORMAT format) {
-        mHasDepth = true;
+        mHasDepthOrStencil = true;
         mRenderPassDepthStencilDesc.DepthBeginningAccess.Type = D3D12BeginningAccessType(loadOp);
         if (loadOp == wgpu::LoadOp::Clear) {
             mRenderPassDepthStencilDesc.DepthBeginningAccess.Clear.ClearValue.DepthStencil.Depth =
@@ -218,6 +218,7 @@ namespace dawn::native::d3d12 {
                                              wgpu::StoreOp storeOp,
                                              uint8_t clearStencil,
                                              DXGI_FORMAT format) {
+        mHasDepthOrStencil = true;
         mRenderPassDepthStencilDesc.StencilBeginningAccess.Type = D3D12BeginningAccessType(loadOp);
         if (loadOp == wgpu::LoadOp::Clear) {
             mRenderPassDepthStencilDesc.StencilBeginningAccess.Clear.ClearValue.DepthStencil

src/dawn/native/d3d12/RenderPassBuilderD3D12.h

@@ -52,7 +52,7 @@ namespace dawn::native::d3d12 {
         // Returns attachment RTVs to use with OMSetRenderTargets.
         const D3D12_CPU_DESCRIPTOR_HANDLE* GetRenderTargetViews() const;
 
-        bool HasDepth() const;
+        bool HasDepthOrStencil() const;
 
         // Functions that set the appropriate values in the render pass descriptors.
         void SetDepthAccess(wgpu::LoadOp loadOp,
@@ -83,7 +83,7 @@ namespace dawn::native::d3d12 {
 
       private:
         ColorAttachmentIndex mHighestColorAttachmentIndexPlusOne{uint8_t(0)};
-        bool mHasDepth = false;
+        bool mHasDepthOrStencil = false;
         D3D12_RENDER_PASS_FLAGS mRenderPassFlags = D3D12_RENDER_PASS_FLAG_NONE;
         D3D12_RENDER_PASS_DEPTH_STENCIL_DESC mRenderPassDepthStencilDesc;
         ityp::

src/dawn/native/d3d12/RenderPipelineD3D12.cpp

@@ -279,7 +279,11 @@ namespace dawn::native::d3d12 {
 
         D3D12_DEPTH_STENCIL_DESC ComputeDepthStencilDesc(const DepthStencilState* descriptor) {
             D3D12_DEPTH_STENCIL_DESC mDepthStencilDescriptor;
-            mDepthStencilDescriptor.DepthEnable = TRUE;
+            mDepthStencilDescriptor.DepthEnable =
+                (descriptor->depthCompare == wgpu::CompareFunction::Always &&
+                 !descriptor->depthWriteEnabled)
+                    ? FALSE
+                    : TRUE;
             mDepthStencilDescriptor.DepthWriteMask = descriptor->depthWriteEnabled
                                                          ? D3D12_DEPTH_WRITE_MASK_ALL
                                                          : D3D12_DEPTH_WRITE_MASK_ZERO;

src/dawn/native/d3d12/ResourceAllocatorManagerD3D12.cpp

@@ -299,7 +299,8 @@ namespace dawn::native::d3d12 {
         // incorrectly allocate a mismatched size.
         if (resourceInfo.SizeInBytes == 0 ||
             resourceInfo.SizeInBytes == std::numeric_limits<uint64_t>::max()) {
-            return DAWN_OUT_OF_MEMORY_ERROR("Resource allocation size was invalid.");
+            return DAWN_OUT_OF_MEMORY_ERROR(absl::StrFormat(
+                "Resource allocation size (%u) was invalid.", resourceInfo.SizeInBytes));
         }
 
         BuddyMemoryAllocator* allocator =

src/dawn/native/d3d12/TextureD3D12.cpp

@@ -178,6 +178,8 @@ namespace dawn::native::d3d12 {
                 case wgpu::TextureFormat::Depth24Plus:
                     return DXGI_FORMAT_R32_TYPELESS;
 
+                // Depth24UnormStencil8 is the smallest format supported on D3D12 that has stencil.
+                case wgpu::TextureFormat::Stencil8:
                 case wgpu::TextureFormat::Depth24UnormStencil8:
                     return DXGI_FORMAT_R24G8_TYPELESS;
                 case wgpu::TextureFormat::Depth24PlusStencil8:
@@ -253,8 +255,6 @@ namespace dawn::native::d3d12 {
                 case wgpu::TextureFormat::ASTC12x12UnormSrgb:
 
                 case wgpu::TextureFormat::R8BG8Biplanar420Unorm:
-                // TODO(dawn:666): implement stencil8
-                case wgpu::TextureFormat::Stencil8:
                 case wgpu::TextureFormat::Undefined:
                     UNREACHABLE();
             }
@@ -346,6 +346,8 @@ namespace dawn::native::d3d12 {
             case wgpu::TextureFormat::Depth32Float:
             case wgpu::TextureFormat::Depth24Plus:
                 return DXGI_FORMAT_D32_FLOAT;
+            // Depth24UnormStencil8 is the smallest format supported on D3D12 that has stencil.
+            case wgpu::TextureFormat::Stencil8:
             case wgpu::TextureFormat::Depth24UnormStencil8:
                 return DXGI_FORMAT_D24_UNORM_S8_UINT;
             case wgpu::TextureFormat::Depth24PlusStencil8:
@@ -424,8 +426,6 @@ namespace dawn::native::d3d12 {
             case wgpu::TextureFormat::ASTC12x12Unorm:
             case wgpu::TextureFormat::ASTC12x12UnormSrgb:
 
-            // TODO(dawn:666): implement stencil8
-            case wgpu::TextureFormat::Stencil8:
             case wgpu::TextureFormat::Undefined:
                 UNREACHABLE();
         }
@@ -684,6 +684,7 @@ namespace dawn::native::d3d12 {
             case wgpu::TextureFormat::Depth24UnormStencil8:
             case wgpu::TextureFormat::Depth24PlusStencil8:
             case wgpu::TextureFormat::Depth32FloatStencil8:
+            case wgpu::TextureFormat::Stencil8:
                 switch (aspect) {
                     case Aspect::Depth:
                         return DXGI_FORMAT_R32_FLOAT;
@@ -1179,6 +1180,7 @@ namespace dawn::native::d3d12 {
                 case wgpu::TextureFormat::Depth16Unorm:
                     mSrvDesc.Format = DXGI_FORMAT_R16_UNORM;
                     break;
+                case wgpu::TextureFormat::Stencil8:
                 case wgpu::TextureFormat::Depth24UnormStencil8:
                     switch (descriptor->aspect) {
                         case wgpu::TextureAspect::DepthOnly:

src/dawn/native/metal/TextureMTL.mm

@@ -289,6 +289,8 @@ namespace dawn::native::metal {
                     // TODO (dawn:1181): Allow non-conformant implementation on macOS 10.11
                     UNREACHABLE();
                 }
+            case wgpu::TextureFormat::Stencil8:
+                return MTLPixelFormatStencil8;
 
 #if defined(DAWN_PLATFORM_MACOS)
             case wgpu::TextureFormat::Depth24UnormStencil8:
@@ -383,8 +385,6 @@ namespace dawn::native::metal {
             case wgpu::TextureFormat::ASTC12x12Unorm:
             case wgpu::TextureFormat::ASTC12x12UnormSrgb:
 
-            // TODO(dawn:666): implement stencil8
-            case wgpu::TextureFormat::Stencil8:
             case wgpu::TextureFormat::Undefined:
                 UNREACHABLE();
         }

src/dawn/native/opengl/GLFormat.cpp

@@ -95,6 +95,7 @@ namespace dawn::native::opengl {
         AddFormat(wgpu::TextureFormat::Depth24Plus, GL_DEPTH_COMPONENT32F, GL_DEPTH_COMPONENT, GL_FLOAT, Type::DepthStencil);
         AddFormat(wgpu::TextureFormat::Depth24PlusStencil8, GL_DEPTH32F_STENCIL8, GL_DEPTH_STENCIL, GL_FLOAT_32_UNSIGNED_INT_24_8_REV, Type::DepthStencil);
         AddFormat(wgpu::TextureFormat::Depth16Unorm, GL_DEPTH_COMPONENT16, GL_DEPTH_COMPONENT, GL_UNSIGNED_SHORT, Type::DepthStencil);
+        AddFormat(wgpu::TextureFormat::Stencil8, GL_STENCIL_INDEX8, GL_STENCIL, GL_UNSIGNED_BYTE, Type::DepthStencil);
 
         // Block compressed formats
         AddFormat(wgpu::TextureFormat::BC1RGBAUnorm, GL_COMPRESSED_RGBA_S3TC_DXT1_EXT, GL_RGBA, GL_UNSIGNED_BYTE, Type::Float);

src/dawn/native/opengl/UtilsGL.cpp

@@ -46,6 +46,9 @@ namespace dawn::native::opengl {
     GLint GetStencilMaskFromStencilFormat(wgpu::TextureFormat depthStencilFormat) {
         switch (depthStencilFormat) {
             case wgpu::TextureFormat::Depth24PlusStencil8:
+            case wgpu::TextureFormat::Depth24UnormStencil8:
+            case wgpu::TextureFormat::Depth32FloatStencil8:
+            case wgpu::TextureFormat::Stencil8:
                 return 0xFF;
 
             default:

src/dawn/native/vulkan/AdapterVk.cpp

@@ -44,7 +44,7 @@ namespace dawn::native::vulkan {
 
     bool Adapter::IsDepthStencilFormatSupported(VkFormat format) {
         ASSERT(format == VK_FORMAT_D16_UNORM_S8_UINT || format == VK_FORMAT_D24_UNORM_S8_UINT ||
-               format == VK_FORMAT_D32_SFLOAT_S8_UINT);
+               format == VK_FORMAT_D32_SFLOAT_S8_UINT || format == VK_FORMAT_S8_UINT);
 
         VkFormatProperties properties;
         mVulkanInstance->GetFunctions().GetPhysicalDeviceFormatProperties(mPhysicalDevice, format,

src/dawn/native/vulkan/DeviceVk.cpp

@@ -93,9 +93,9 @@ namespace dawn::native::vulkan {
 
         DAWN_TRY(PrepareRecordingContext());
 
-        // The environment can request to use D32S8 or D24S8 when it's not available. Override
+        // The environment can request to various options for depth-stencil formats that could be
-        // the decision if it is not applicable.
+        // unavailable. Override the decision if it is not applicable.
-        ApplyDepth24PlusS8Toggle();
+        ApplyDepthStencilFormatToggles();
 
         // The environment can only request to use VK_KHR_zero_initialize_workgroup_memory when the
         // extension is available. Override the decision if it is no applicable.
@@ -518,13 +518,17 @@ namespace dawn::native::vulkan {
         // By default try to initialize workgroup memory with OpConstantNull according to the Vulkan
         // extension VK_KHR_zero_initialize_workgroup_memory.
         SetToggle(Toggle::VulkanUseZeroInitializeWorkgroupMemoryExtension, true);
+
+        // By default try to use S8 if available.
+        SetToggle(Toggle::VulkanUseS8, true);
     }
 
-    void Device::ApplyDepth24PlusS8Toggle() {
+    void Device::ApplyDepthStencilFormatToggles() {
         bool supportsD32s8 =
             ToBackend(GetAdapter())->IsDepthStencilFormatSupported(VK_FORMAT_D32_SFLOAT_S8_UINT);
         bool supportsD24s8 =
             ToBackend(GetAdapter())->IsDepthStencilFormatSupported(VK_FORMAT_D24_UNORM_S8_UINT);
+        bool supportsS8 = ToBackend(GetAdapter())->IsDepthStencilFormatSupported(VK_FORMAT_S8_UINT);
 
         ASSERT(supportsD32s8 || supportsD24s8);
 
@@ -534,6 +538,9 @@ namespace dawn::native::vulkan {
         if (!supportsD32s8) {
             ForceSetToggle(Toggle::VulkanUseD32S8, false);
         }
+        if (!supportsS8) {
+            ForceSetToggle(Toggle::VulkanUseS8, false);
+        }
     }
 
     void Device::ApplyUseZeroInitializeWorkgroupMemoryExtensionToggle() {

src/dawn/native/vulkan/DeviceVk.h

@@ -151,7 +151,7 @@ namespace dawn::native::vulkan {
 
         uint32_t FindComputeSubgroupSize() const;
         void InitTogglesFromDriver();
-        void ApplyDepth24PlusS8Toggle();
+        void ApplyDepthStencilFormatToggles();
         void ApplyUseZeroInitializeWorkgroupMemoryExtensionToggle();
 
         void DestroyImpl() override;

src/dawn/native/vulkan/TextureVk.cpp

@@ -318,6 +318,14 @@ namespace dawn::native::vulkan {
                 return VK_FORMAT_D24_UNORM_S8_UINT;
             case wgpu::TextureFormat::Depth32FloatStencil8:
                 return VK_FORMAT_D32_SFLOAT_S8_UINT;
+            case wgpu::TextureFormat::Stencil8:
+                // Try to use the stencil8 format if possible, otherwise use whatever format we can
+                // use that contains a stencil8 component.
+                if (device->IsToggleEnabled(Toggle::VulkanUseS8)) {
+                    return VK_FORMAT_S8_UINT;
+                } else {
+                    return VulkanImageFormat(device, wgpu::TextureFormat::Depth24PlusStencil8);
+                }
 
             case wgpu::TextureFormat::BC1RGBAUnorm:
                 return VK_FORMAT_BC1_RGBA_UNORM_BLOCK;
@@ -429,8 +437,6 @@ namespace dawn::native::vulkan {
             case wgpu::TextureFormat::R8BG8Biplanar420Unorm:
                 return VK_FORMAT_G8_B8R8_2PLANE_420_UNORM;
 
-            // TODO(dawn:666): implement stencil8
-            case wgpu::TextureFormat::Stencil8:
             case wgpu::TextureFormat::Undefined:
                 break;
         }
@@ -982,6 +988,12 @@ namespace dawn::native::vulkan {
     // single plane in a new SubresourceStorage<TextureUsage>. The barriers will be produced
     // for DEPTH | STENCIL since the SubresourceRange uses Aspect::CombinedDepthStencil.
     bool Texture::ShouldCombineDepthStencilBarriers() const {
+        // If the Stencil8 format is being emulated then memory barriers also need to include
+        // the depth aspect. (See: crbug.com/dawn/1331)
+        if (GetFormat().format == wgpu::TextureFormat::Stencil8 &&
+            !GetDevice()->IsToggleEnabled(Toggle::VulkanUseS8)) {
+            return true;
+        }
         return GetFormat().aspects == (Aspect::Depth | Aspect::Stencil);
     }
 

src/dawn/tests/end2end/DepthStencilCopyTests.cpp

@@ -126,53 +126,6 @@ class DepthStencilCopyTests : public DawnTestWithParams<DepthStencilCopyTestPara
         return device.CreateTexture(&texDescriptor);
     }
 
-    void PopulatePipelineDescriptorWriteDepth(utils::ComboRenderPipelineDescriptor* desc,
-                                              wgpu::TextureFormat format,
-                                              float regionDepth) {
-        desc->vertex.module = mVertexModule;
-
-        std::string fsSource = R"(
-        @stage(fragment) fn main() -> @builtin(frag_depth) f32 {
-            return )" + std::to_string(regionDepth) +
-                               ";\n}";
-
-        desc->cFragment.module = utils::CreateShaderModule(device, fsSource.c_str());
-        wgpu::DepthStencilState* depthStencil = desc->EnableDepthStencil(format);
-        depthStencil->depthWriteEnabled = true;
-        desc->cFragment.targetCount = 0;
-    }
-
-    // Initialize the depth/stencil values for the texture using a render pass.
-    // The texture will be cleared to the "clear" value, and then bottom left corner will
-    // be written with the "region" value.
-    void InitializeDepthTextureRegion(wgpu::Texture texture,
-                                      wgpu::TextureFormat depthFormat,
-                                      float clearDepth,
-                                      float regionDepth,
-                                      uint32_t mipLevel = 0) {
-        wgpu::TextureViewDescriptor viewDesc = {};
-        viewDesc.baseMipLevel = mipLevel;
-        viewDesc.mipLevelCount = 1;
-
-        utils::ComboRenderPassDescriptor renderPassDesc({}, texture.CreateView(&viewDesc));
-        renderPassDesc.UnsetDepthStencilLoadStoreOpsForFormat(depthFormat);
-        renderPassDesc.cDepthStencilAttachmentInfo.depthClearValue = clearDepth;
-
-        utils::ComboRenderPipelineDescriptor renderPipelineDesc;
-        PopulatePipelineDescriptorWriteDepth(&renderPipelineDesc, GetParam().mTextureFormat,
-                                             regionDepth);
-
-        wgpu::RenderPipeline pipeline = device.CreateRenderPipeline(&renderPipelineDesc);
-        wgpu::CommandEncoder commandEncoder = device.CreateCommandEncoder();
-        wgpu::RenderPassEncoder pass = commandEncoder.BeginRenderPass(&renderPassDesc);
-        pass.SetPipeline(pipeline);
-        pass.Draw(6);
-        pass.End();
-
-        wgpu::CommandBuffer commands = commandEncoder.Finish();
-        queue.Submit(1, &commands);
-    }
-
     // Initialize the depth/stencil values for the texture using a render pass.
     // The texture will be cleared to the "clear" values, and then bottom left corner will
     // be written with the "region" values.
@@ -182,21 +135,43 @@ class DepthStencilCopyTests : public DawnTestWithParams<DepthStencilCopyTestPara
                                              uint8_t clearStencil,
                                              uint8_t regionStencil,
                                              uint32_t mipLevel = 0) {
+        wgpu::TextureFormat format = GetParam().mTextureFormat;
+        // Create the render pass used for the initialization.
+        utils::ComboRenderPipelineDescriptor renderPipelineDesc;
+        renderPipelineDesc.vertex.module = mVertexModule;
+        renderPipelineDesc.cFragment.targetCount = 0;
+
+        wgpu::DepthStencilState* depthStencil = renderPipelineDesc.EnableDepthStencil(format);
+
+        if (utils::IsStencilOnlyFormat(format)) {
+            depthStencil->depthCompare = wgpu::CompareFunction::Always;
+            renderPipelineDesc.cFragment.module = utils::CreateShaderModule(device, R"(
+                @stage(fragment) fn main() {}
+            )");
+        } else {
+            depthStencil->depthWriteEnabled = true;
+            renderPipelineDesc.cFragment.module = utils::CreateShaderModule(device, std::string(R"(
+                @stage(fragment) fn main() -> @builtin(frag_depth) f32 {
+                    return )" + std::to_string(regionDepth) + R"(;
+                })")
+                                                                                        .c_str());
+        }
+        if (!utils::IsDepthOnlyFormat(format)) {
+            depthStencil->stencilFront.passOp = wgpu::StencilOperation::Replace;
+        }
+
+        wgpu::RenderPipeline pipeline = device.CreateRenderPipeline(&renderPipelineDesc);
+
+        // Build the render pass used for initialization.
         wgpu::TextureViewDescriptor viewDesc = {};
         viewDesc.baseMipLevel = mipLevel;
         viewDesc.mipLevelCount = 1;
 
         utils::ComboRenderPassDescriptor renderPassDesc({}, texture.CreateView(&viewDesc));
+        renderPassDesc.UnsetDepthStencilLoadStoreOpsForFormat(format);
         renderPassDesc.cDepthStencilAttachmentInfo.depthClearValue = clearDepth;
         renderPassDesc.cDepthStencilAttachmentInfo.stencilClearValue = clearStencil;
 
-        utils::ComboRenderPipelineDescriptor renderPipelineDesc;
-        PopulatePipelineDescriptorWriteDepth(&renderPipelineDesc, GetParam().mTextureFormat,
-                                             regionDepth);
-        renderPipelineDesc.cDepthStencil.stencilFront.passOp = wgpu::StencilOperation::Replace;
-
-        wgpu::RenderPipeline pipeline = device.CreateRenderPipeline(&renderPipelineDesc);
-
         // Draw the quad (two triangles)
         wgpu::CommandEncoder commandEncoder = device.CreateCommandEncoder();
         wgpu::RenderPassEncoder pass = commandEncoder.BeginRenderPass(&renderPassDesc);
@@ -471,7 +446,7 @@ TEST_P(DepthCopyTests, FromDepthAspect) {
         kWidth, kHeight, wgpu::TextureUsage::RenderAttachment | wgpu::TextureUsage::CopySrc);
 
     constexpr float kInitDepth = 0.2f;
-    InitializeDepthTextureRegion(texture, GetParam().mTextureFormat, 0.f, kInitDepth);
+    InitializeDepthStencilTextureRegion(texture, 0.f, kInitDepth, 0, 0);
 
     // This expectation is the test as it performs the CopyTextureToBuffer.
     if (GetParam().mTextureFormat == wgpu::TextureFormat::Depth16Unorm) {
@@ -511,7 +486,7 @@ TEST_P(DepthCopyTests, FromNonZeroMipDepthAspect) {
         9, 9, wgpu::TextureUsage::RenderAttachment | wgpu::TextureUsage::CopySrc, 2);
 
     constexpr float kInitDepth = 0.4f;
-    InitializeDepthTextureRegion(depthTexture, GetParam().mTextureFormat, 0.f, kInitDepth, 1);
+    InitializeDepthStencilTextureRegion(depthTexture, 0.f, kInitDepth, 0, 0, /*mipLevel*/ 1);
 
     // This expectation is the test as it performs the CopyTextureToBuffer.
     if (GetParam().mTextureFormat == wgpu::TextureFormat::Depth16Unorm) {
@@ -670,17 +645,19 @@ TEST_P(StencilCopyTests, ToStencilAspect) {
     // Create a stencil texture
     constexpr uint32_t kWidth = 4;
     constexpr uint32_t kHeight = 4;
+    const bool hasDepth = !utils::IsStencilOnlyFormat(GetParam().mTextureFormat);
 
     wgpu::Texture depthStencilTexture =
         CreateDepthStencilTexture(kWidth, kHeight,
                                   wgpu::TextureUsage::RenderAttachment |
                                       wgpu::TextureUsage::CopySrc | wgpu::TextureUsage::CopyDst);
 
-    {
+    if (hasDepth) {
         wgpu::CommandEncoder commandEncoder = device.CreateCommandEncoder();
 
         // Clear depth to 0.7, so we can check that the stencil copy doesn't mutate the depth.
         utils::ComboRenderPassDescriptor passDescriptor({}, depthStencilTexture.CreateView());
+        passDescriptor.UnsetDepthStencilLoadStoreOpsForFormat(GetParam().mTextureFormat);
         passDescriptor.cDepthStencilAttachmentInfo.depthClearValue = 0.7;
 
         wgpu::RenderPassEncoder pass = commandEncoder.BeginRenderPass(&passDescriptor);
@@ -727,10 +704,14 @@ TEST_P(StencilCopyTests, ToStencilAspect) {
         renderPipelineDesc.cFragment.module = utils::CreateShaderModule(device, R"(
             @stage(fragment) fn main() {
             })");
+        renderPipelineDesc.cFragment.targetCount = 0;
         wgpu::DepthStencilState* depthStencil =
             renderPipelineDesc.EnableDepthStencil(GetParam().mTextureFormat);
         depthStencil->stencilFront.passOp = wgpu::StencilOperation::DecrementClamp;
-        renderPipelineDesc.cFragment.targetCount = 0;
+        if (!hasDepth) {
+            depthStencil->depthWriteEnabled = false;
+            depthStencil->depthCompare = wgpu::CompareFunction::Always;
+        }
 
         wgpu::RenderPipeline pipeline = device.CreateRenderPipeline(&renderPipelineDesc);
 
@@ -739,6 +720,7 @@ TEST_P(StencilCopyTests, ToStencilAspect) {
         utils::ComboRenderPassDescriptor passDescriptor({}, depthStencilTexture.CreateView());
         passDescriptor.cDepthStencilAttachmentInfo.stencilLoadOp = wgpu::LoadOp::Load;
         passDescriptor.cDepthStencilAttachmentInfo.depthLoadOp = wgpu::LoadOp::Load;
+        passDescriptor.UnsetDepthStencilLoadStoreOpsForFormat(GetParam().mTextureFormat);
 
         // Draw the quad in the bottom left (two triangles).
         wgpu::RenderPassEncoder pass = commandEncoder.BeginRenderPass(&passDescriptor);
@@ -754,8 +736,9 @@ TEST_P(StencilCopyTests, ToStencilAspect) {
     EXPECT_TEXTURE_EQ(expectedStencilData.data(), depthStencilTexture, {0, 0}, {kWidth, kHeight}, 0,
                       wgpu::TextureAspect::StencilOnly);
 
-    ExpectAttachmentDepthTestData(depthStencilTexture, GetParam().mTextureFormat, kWidth, kHeight,
+    if (hasDepth) {
-                                  0, 0,
+        ExpectAttachmentDepthTestData(depthStencilTexture, GetParam().mTextureFormat, kWidth,
+                                      kHeight, 0, 0,
                                       {
                                           0.7, 0.7, 0.7, 0.7,  //
                                           0.7, 0.7, 0.7, 0.7,  //
@@ -763,10 +746,13 @@ TEST_P(StencilCopyTests, ToStencilAspect) {
                                           0.7, 0.7, 0.7, 0.7,  //
                                       });
     }
+}
 
 DAWN_INSTANTIATE_TEST_P(DepthStencilCopyTests,
                         {D3D12Backend(), MetalBackend(), OpenGLBackend(), OpenGLESBackend(),
-                         VulkanBackend()},
+                         // Test with the vulkan_use_s8 toggle forced on and off.
+                         VulkanBackend({"vulkan_use_s8"}, {}),
+                         VulkanBackend({}, {"vulkan_use_s8"})},
                         std::vector<wgpu::TextureFormat>(utils::kDepthAndStencilFormats.begin(),
                                                          utils::kDepthAndStencilFormats.end()));
 
@@ -784,6 +770,8 @@ DAWN_INSTANTIATE_TEST_P(DepthCopyFromBufferTests,
 
 DAWN_INSTANTIATE_TEST_P(StencilCopyTests,
                         {D3D12Backend(), MetalBackend(), OpenGLBackend(), OpenGLESBackend(),
-                         VulkanBackend()},
+                         // Test with the vulkan_use_s8 toggle forced on and off.
+                         VulkanBackend({"vulkan_use_s8"}, {}),
+                         VulkanBackend({}, {"vulkan_use_s8"})},
                         std::vector<wgpu::TextureFormat>(utils::kStencilFormats.begin(),
                                                          utils::kStencilFormats.end()));

src/dawn/utils/TextureUtils.cpp

@@ -215,12 +215,17 @@ namespace utils {
         }
     }
 
+    bool IsStencilOnlyFormat(wgpu::TextureFormat textureFormat) {
+        return textureFormat == wgpu::TextureFormat::Stencil8;
+    }
+
     uint32_t GetTexelBlockSizeInBytes(wgpu::TextureFormat textureFormat) {
         switch (textureFormat) {
             case wgpu::TextureFormat::R8Unorm:
             case wgpu::TextureFormat::R8Snorm:
             case wgpu::TextureFormat::R8Uint:
             case wgpu::TextureFormat::R8Sint:
+            case wgpu::TextureFormat::Stencil8:
                 return 1u;
 
             case wgpu::TextureFormat::R16Uint:
@@ -339,8 +344,6 @@ namespace utils {
             // Block size of a multi-planar format depends on aspect.
             case wgpu::TextureFormat::R8BG8Biplanar420Unorm:
 
-            // TODO(dawn:666): implement stencil8
-            case wgpu::TextureFormat::Stencil8:
             case wgpu::TextureFormat::Undefined:
                 break;
         }
@@ -391,6 +394,7 @@ namespace utils {
             case wgpu::TextureFormat::Depth16Unorm:
             case wgpu::TextureFormat::Depth24UnormStencil8:
             case wgpu::TextureFormat::Depth32FloatStencil8:
+            case wgpu::TextureFormat::Stencil8:
                 return 1u;
 
             case wgpu::TextureFormat::BC1RGBAUnorm:
@@ -457,8 +461,6 @@ namespace utils {
             // Block size of a multi-planar format depends on aspect.
             case wgpu::TextureFormat::R8BG8Biplanar420Unorm:
 
-            // TODO(dawn:666): implement stencil8
-            case wgpu::TextureFormat::Stencil8:
             case wgpu::TextureFormat::Undefined:
                 break;
         }
@@ -509,6 +511,7 @@ namespace utils {
             case wgpu::TextureFormat::Depth16Unorm:
             case wgpu::TextureFormat::Depth24UnormStencil8:
             case wgpu::TextureFormat::Depth32FloatStencil8:
+            case wgpu::TextureFormat::Stencil8:
                 return 1u;
 
             case wgpu::TextureFormat::BC1RGBAUnorm:
@@ -575,8 +578,6 @@ namespace utils {
             // Block size of a multi-planar format depends on aspect.
             case wgpu::TextureFormat::R8BG8Biplanar420Unorm:
 
-            // TODO(dawn:666): implement stencil8
-            case wgpu::TextureFormat::Stencil8:
             case wgpu::TextureFormat::Undefined:
                 break;
         }

src/dawn/utils/TextureUtils.h

@@ -22,8 +22,7 @@
 #include "dawn/common/Assert.h"
 
 namespace utils {
-    // TODO(dawn:666): Add Stencil8 format when it's implemented.
+    static constexpr std::array<wgpu::TextureFormat, 95> kAllTextureFormats = {
-    static constexpr std::array<wgpu::TextureFormat, 94> kAllTextureFormats = {
         wgpu::TextureFormat::R8Unorm,
         wgpu::TextureFormat::R8Snorm,
         wgpu::TextureFormat::R8Uint,
@@ -66,6 +65,7 @@ namespace utils {
         wgpu::TextureFormat::Depth24PlusStencil8,
         wgpu::TextureFormat::Depth24UnormStencil8,
         wgpu::TextureFormat::Depth32FloatStencil8,
+        wgpu::TextureFormat::Stencil8,
         wgpu::TextureFormat::BC1RGBAUnorm,
         wgpu::TextureFormat::BC1RGBAUnormSrgb,
         wgpu::TextureFormat::BC2RGBAUnorm,
@@ -206,16 +206,16 @@ namespace utils {
                       kBCFormats.size() + kETC2Formats.size() + kASTCFormats.size(),
                   "Number of compressed format must equal number of BC, ETC2, and ASTC formats.");
 
-    // TODO(dawn:666): Add Stencil8 format when it's implemented.
     static constexpr std::array<wgpu::TextureFormat, 6> kDepthFormats = {
         wgpu::TextureFormat::Depth16Unorm,         wgpu::TextureFormat::Depth32Float,
         wgpu::TextureFormat::Depth24Plus,          wgpu::TextureFormat::Depth24PlusStencil8,
         wgpu::TextureFormat::Depth24UnormStencil8, wgpu::TextureFormat::Depth32FloatStencil8,
     };
-    static constexpr std::array<wgpu::TextureFormat, 3> kStencilFormats = {
+    static constexpr std::array<wgpu::TextureFormat, 4> kStencilFormats = {
         wgpu::TextureFormat::Depth24PlusStencil8,
         wgpu::TextureFormat::Depth24UnormStencil8,
         wgpu::TextureFormat::Depth32FloatStencil8,
+        wgpu::TextureFormat::Stencil8,
     };
     static constexpr std::array<wgpu::TextureFormat, 3> kDepthAndStencilFormats = {
         wgpu::TextureFormat::Depth24PlusStencil8,
@@ -230,6 +230,7 @@ namespace utils {
     bool IsASTCTextureFormat(wgpu::TextureFormat textureFormat);
 
     bool IsDepthOnlyFormat(wgpu::TextureFormat textureFormat);
+    bool IsStencilOnlyFormat(wgpu::TextureFormat textureFormat);
 
     bool TextureFormatSupportsMultisampling(wgpu::TextureFormat textureFormat);
     bool TextureFormatSupportsResolveTarget(wgpu::TextureFormat textureFormat);