Validate if depth attachment is present when frag_depth is written

Bug: dawn:1636
Change-Id: I47aa4e5734b8e70e8c5a9171872a44a577d168d7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/116859
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Shrek Shao <shrekshao@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/dawn/native/RenderPipeline.cpp

@@ -335,6 +335,7 @@ MaybeError ValidateColorTargetState(
 MaybeError ValidateFragmentState(DeviceBase* device,
                                  const FragmentState* descriptor,
                                  const PipelineLayoutBase* layout,
+                                 const DepthStencilState* depthStencil,
                                  bool alphaToCoverageEnabled) {
     DAWN_INVALID_IF(descriptor->nextInChain != nullptr, "nextInChain must be nullptr.");
 
@@ -351,6 +352,22 @@ MaybeError ValidateFragmentState(DeviceBase* device,
 
     const EntryPointMetadata& fragmentMetadata =
         descriptor->module->GetEntryPoint(descriptor->entryPoint);
+
+    if (fragmentMetadata.usesFragDepth) {
+        DAWN_INVALID_IF(
+            depthStencil == nullptr,
+            "Depth stencil state is not present when fragment stage (%s, entryPoint: %s) is "
+            "writing to frag_depth.",
+            descriptor->module, descriptor->entryPoint);
+        const Format* depthStencilFormat;
+        DAWN_TRY_ASSIGN(depthStencilFormat, device->GetInternalFormat(depthStencil->format));
+        DAWN_INVALID_IF(!depthStencilFormat->HasDepth(),
+                        "Depth stencil state format (%s) has no depth aspect when fragment stage "
+                        "(%s, entryPoint: %s) is "
+                        "writing to frag_depth.",
+                        depthStencil->format, descriptor->module, descriptor->entryPoint);
+    }
+
     ColorAttachmentFormats colorAttachmentFormats;
     for (ColorAttachmentIndex i(uint8_t(0));
          i < ColorAttachmentIndex(static_cast<uint8_t>(descriptor->targetCount)); ++i) {
@@ -477,6 +494,7 @@ MaybeError ValidateRenderPipelineDescriptor(DeviceBase* device,
 
     if (descriptor->fragment != nullptr) {
         DAWN_TRY_CONTEXT(ValidateFragmentState(device, descriptor->fragment, descriptor->layout,
+                                               descriptor->depthStencil,
                                                descriptor->multisample.alphaToCoverageEnabled),
                          "validating fragment state.");
 

src/dawn/tests/unittests/validation/RenderPipelineValidationTests.cpp

@@ -193,6 +193,52 @@ TEST_F(RenderPipelineValidationTest, DepthStencilAspectRequirement) {
     // enabled when Stencil8 format is implemented
 }
 
+// Tests that depth attachment is required when frag_depth is written in fragment stage.
+TEST_F(RenderPipelineValidationTest, DepthAttachmentRequiredWhenFragDepthIsWritten) {
+    wgpu::ShaderModule fsModuleFragDepthOutput = utils::CreateShaderModule(device, R"(
+        struct Output {
+            @builtin(frag_depth) depth_out: f32,
+            @location(0) color : vec4<f32>,
+        }
+        @fragment fn main() -> Output {
+            var o: Output;
+            // We need to make sure this frag_depth isn't optimized out even its value equals "no op".
+            o.depth_out = 0.5;
+            o.color = vec4<f32>(1.0, 1.0, 1.0, 1.0);
+            return o;
+        }
+    )");
+
+    {
+        // Succeeds because there is depth stencil state.
+        utils::ComboRenderPipelineDescriptor descriptor;
+        descriptor.vertex.module = vsModule;
+        descriptor.cFragment.module = fsModuleFragDepthOutput;
+        descriptor.EnableDepthStencil(wgpu::TextureFormat::Depth24PlusStencil8);
+
+        device.CreateRenderPipeline(&descriptor);
+    }
+
+    {
+        // Fails because there is no depth stencil state.
+        utils::ComboRenderPipelineDescriptor descriptor;
+        descriptor.vertex.module = vsModule;
+        descriptor.cFragment.module = fsModuleFragDepthOutput;
+
+        ASSERT_DEVICE_ERROR(device.CreateRenderPipeline(&descriptor));
+    }
+
+    {
+        // Fails because there is depth stencil state but no depth aspect.
+        utils::ComboRenderPipelineDescriptor descriptor;
+        descriptor.vertex.module = vsModule;
+        descriptor.cFragment.module = fsModuleFragDepthOutput;
+        descriptor.EnableDepthStencil(wgpu::TextureFormat::Stencil8);
+
+        ASSERT_DEVICE_ERROR(device.CreateRenderPipeline(&descriptor));
+    }
+}
+
 // Tests that at least one color target state is required.
 TEST_F(RenderPipelineValidationTest, ColorTargetStateRequired) {
     {