Make vertex input descriptor optional

Following WebGPU spec change at https://github.com/gpuweb/gpuweb/issues/378,
vertexInput descriptor from GPURenderPipelineDescriptor should not be
required anymore.

BUG=dawn:22

Change-Id: I5d2500a758f44b7a7db2d2c23b359f1012221227
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/10640
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Reviewed-by: Austin Eng <enga@chromium.org>

dawn.json

@@ -648,7 +648,7 @@
         "extensible": true,
         "members": [
             {"name": "index format", "type": "index format", "default": "uint32"},
-            {"name": "buffer count", "type": "uint32_t"},
+            {"name": "buffer count", "type": "uint32_t", "default": 0},
             {"name": "buffers", "type": "vertex buffer descriptor", "annotation": "const*", "length": "buffer count"}
         ]
     },
@@ -1031,7 +1031,7 @@
             {"name": "layout", "type": "pipeline layout"},
             {"name": "vertex stage", "type": "pipeline stage descriptor", "annotation": "const*"},
             {"name": "fragment stage", "type": "pipeline stage descriptor", "annotation": "const*", "optional": true},
-            {"name": "vertex input", "type": "vertex input descriptor", "annotation": "const*"},
+            {"name": "vertex input", "type": "vertex input descriptor", "annotation": "const*", "optional": true},
             {"name": "primitive topology", "type": "primitive topology"},
             {"name": "rasterization state", "type": "rasterization state descriptor", "annotation": "const*", "optional": true},
             {"name": "sample count", "type": "uint32_t", "default": "1"},

src/dawn_native/RenderPipeline.cpp

@@ -272,17 +272,16 @@ namespace dawn_native {
 
         DAWN_TRY(device->ValidateObject(descriptor->layout));
 
-        if (descriptor->vertexInput == nullptr) {
-            return DAWN_VALIDATION_ERROR("Input state must not be null");
-        }
-
         // TODO(crbug.com/dawn/136): Support vertex-only pipelines.
         if (descriptor->fragmentStage == nullptr) {
             return DAWN_VALIDATION_ERROR("Null fragment stage is not supported (yet)");
         }
 
         std::bitset<kMaxVertexAttributes> attributesSetMask;
-        DAWN_TRY(ValidateVertexInputDescriptor(descriptor->vertexInput, &attributesSetMask));
+        if (descriptor->vertexInput) {
+            DAWN_TRY(ValidateVertexInputDescriptor(descriptor->vertexInput, &attributesSetMask));
+        }
+
         DAWN_TRY(ValidatePrimitiveTopology(descriptor->primitiveTopology));
         DAWN_TRY(ValidatePipelineStageDescriptor(device, descriptor->vertexStage,
                                                  descriptor->layout, SingleShaderStage::Vertex));
@@ -358,7 +357,6 @@ namespace dawn_native {
         : PipelineBase(device,
                        descriptor->layout,
                        dawn::ShaderStage::Vertex | dawn::ShaderStage::Fragment),
-          mVertexInput(*descriptor->vertexInput),
           mAttachmentState(device->GetOrCreateAttachmentState(descriptor)),
           mPrimitiveTopology(descriptor->primitiveTopology),
           mSampleMask(descriptor->sampleMask),
@@ -368,6 +366,12 @@ namespace dawn_native {
           mFragmentModule(descriptor->fragmentStage->module),
           mFragmentEntryPoint(descriptor->fragmentStage->entryPoint),
           mIsBlueprint(blueprint) {
+        if (descriptor->vertexInput != nullptr) {
+            mVertexInput = *descriptor->vertexInput;
+        } else {
+            mVertexInput = VertexInputDescriptor();
+        }
+
         for (uint32_t slot = 0; slot < mVertexInput.bufferCount; ++slot) {
             if (mVertexInput.buffers[slot].attributeCount == 0) {
                 continue;

src/tests/end2end/VertexInputTests.cpp

@@ -518,3 +518,52 @@ DAWN_INSTANTIATE_TEST(VertexInputTest, D3D12Backend, MetalBackend, OpenGLBackend
 //  - Add checks for alignement of vertex buffers and attributes if needed
 //  - Check for attribute narrowing
 //  - Check that the input state and the pipeline vertex input types match
+
+class OptionalVertexInputTest : public DawnTest {};
+
+// Test that vertex input is not required in render pipeline descriptor.
+TEST_P(OptionalVertexInputTest, Basic) {
+    utils::BasicRenderPass renderPass = utils::CreateBasicRenderPass(device, 3, 3);
+
+    dawn::ShaderModule vsModule =
+        utils::CreateShaderModule(device, utils::SingleShaderStage::Vertex, R"(
+            #version 450
+            void main() {
+                gl_Position = vec4(0.0f, 0.0f, 0.0f, 1.0f);
+            })");
+
+    dawn::ShaderModule fsModule =
+        utils::CreateShaderModule(device, utils::SingleShaderStage::Fragment, R"(
+            #version 450
+            layout(location = 0) out vec4 fragColor;
+            void main() {
+                fragColor = vec4(0.0f, 1.0f, 0.0f, 1.0f);
+            })");
+
+    utils::ComboRenderPipelineDescriptor descriptor(device);
+    descriptor.cVertexStage.module = vsModule;
+    descriptor.cFragmentStage.module = fsModule;
+    descriptor.primitiveTopology = dawn::PrimitiveTopology::PointList;
+    descriptor.vertexInput = nullptr;
+
+    dawn::RenderPipeline pipeline = device.CreateRenderPipeline(&descriptor);
+
+    dawn::CommandEncoder encoder = device.CreateCommandEncoder();
+    {
+        dawn::RenderPassEncoder pass = encoder.BeginRenderPass(&renderPass.renderPassInfo);
+        pass.SetPipeline(pipeline);
+        pass.Draw(1, 1, 0, 0);
+        pass.EndPass();
+    }
+
+    dawn::CommandBuffer commands = encoder.Finish();
+    queue.Submit(1, &commands);
+
+    EXPECT_PIXEL_RGBA8_EQ(RGBA8(0, 255, 0, 255), renderPass.color, 1, 1);
+}
+
+DAWN_INSTANTIATE_TEST(OptionalVertexInputTest,
+                      D3D12Backend,
+                      MetalBackend,
+                      OpenGLBackend,
+                      VulkanBackend);

src/tests/unittests/validation/RenderPipelineValidationTests.cpp

@@ -43,11 +43,31 @@ class RenderPipelineValidationTest : public ValidationTest {
 
 // Test cases where creation should succeed
 TEST_F(RenderPipelineValidationTest, CreationSuccess) {
-    utils::ComboRenderPipelineDescriptor descriptor(device);
+    {
-    descriptor.cVertexStage.module = vsModule;
+        utils::ComboRenderPipelineDescriptor descriptor(device);
-    descriptor.cFragmentStage.module = fsModule;
+        descriptor.cVertexStage.module = vsModule;
+        descriptor.cFragmentStage.module = fsModule;
 
-    device.CreateRenderPipeline(&descriptor);
+        device.CreateRenderPipeline(&descriptor);
+    }
+    {
+        // Vertex input should be optional
+        utils::ComboRenderPipelineDescriptor descriptor(device);
+        descriptor.cVertexStage.module = vsModule;
+        descriptor.cFragmentStage.module = fsModule;
+        descriptor.vertexInput = nullptr;
+
+        device.CreateRenderPipeline(&descriptor);
+    }
+    {
+        // Rasterization state should be optional
+        utils::ComboRenderPipelineDescriptor descriptor(device);
+        descriptor.cVertexStage.module = vsModule;
+        descriptor.cFragmentStage.module = fsModule;
+        descriptor.rasterizationState = nullptr;
+
+        device.CreateRenderPipeline(&descriptor);
+    }
 }
 
 // Tests that at least one color state is required.