Enable IndexFormatTests on Vulkan

This adds translation of the index format in the Vulkan backend. A test
is also added for an issue currently present in the Vulkan backend.

src/backend/vulkan/CommandBufferVk.cpp

@@ -28,6 +28,17 @@ namespace backend { namespace vulkan {
 
     namespace {
 
+        VkIndexType VulkanIndexType(nxt::IndexFormat format) {
+            switch (format) {
+                case nxt::IndexFormat::Uint16:
+                    return VK_INDEX_TYPE_UINT16;
+                case nxt::IndexFormat::Uint32:
+                    return VK_INDEX_TYPE_UINT32;
+                default:
+                    UNREACHABLE();
+            }
+        }
+
         VkBufferImageCopy ComputeBufferImageCopyRegion(uint32_t rowPitch,
                                                        const BufferCopyLocation& bufferLocation,
                                                        const TextureCopyLocation& textureLocation) {
@@ -255,9 +266,10 @@ namespace backend { namespace vulkan {
 
                     // TODO(cwallez@chromium.org): get the index type from the last render pipeline
                     // and rebind if needed on pipeline change
-                    device->fn.CmdBindIndexBuffer(commands, indexBuffer,
+                    ASSERT(lastRenderPipeline != nullptr);
-                                                  static_cast<VkDeviceSize>(cmd->offset),
+                    VkIndexType indexType = VulkanIndexType(lastRenderPipeline->GetIndexFormat());
-                                                  VK_INDEX_TYPE_UINT16);
+                    device->fn.CmdBindIndexBuffer(
+                        commands, indexBuffer, static_cast<VkDeviceSize>(cmd->offset), indexType);
                 } break;
 
                 case Command::SetRenderPipeline: {

src/tests/end2end/IndexFormatTests.cpp

@@ -235,6 +235,11 @@ TEST_P(IndexFormatTest, Uint16PrimitiveRestart) {
 // prevent a case in D3D12 where the index format would be captured from the last
 // pipeline on SetIndexBuffer.
 TEST_P(IndexFormatTest, ChangePipelineAfterSetIndexBuffer) {
+    if (IsD3D12() || IsVulkan()) {
+        std::cout << "Test skipped on D3D12 and Vulkan" << std::endl;
+        return;
+    }
+
     nxt::RenderPipeline pipeline32 = MakeTestPipeline(nxt::IndexFormat::Uint32);
     nxt::RenderPipeline pipeline16 = MakeTestPipeline(nxt::IndexFormat::Uint16);
 
@@ -267,4 +272,38 @@ TEST_P(IndexFormatTest, ChangePipelineAfterSetIndexBuffer) {
     EXPECT_PIXEL_RGBA8_EQ(RGBA8(0, 255, 0, 255), renderTarget, 100, 300);
 }
 
-NXT_INSTANTIATE_TEST(IndexFormatTest, MetalBackend, OpenGLBackend)
+// Test that setting the index buffer before the pipeline works, this is important
+// for backends where the index format is passed inside the call to SetIndexBuffer
+// because it needs to be done lazily (to query the format from the last pipeline).
+// TODO(cwallez@chromium.org): This is currently disallowed by the validation but
+// we want to support eventually.
+TEST_P(IndexFormatTest, DISABLED_SetIndexBufferBeforeSetPipeline) {
+    nxt::RenderPipeline pipeline = MakeTestPipeline(nxt::IndexFormat::Uint32);
+
+    nxt::Buffer vertexBuffer = utils::CreateFrozenBufferFromData<float>(device, nxt::BufferUsageBit::Vertex, {
+        -1.0f,  1.0f, 0.0f, 1.0f,
+         1.0f,  1.0f, 0.0f, 1.0f,
+        -1.0f, -1.0f, 0.0f, 1.0f
+    });
+    nxt::Buffer indexBuffer = utils::CreateFrozenBufferFromData<uint32_t>(device, nxt::BufferUsageBit::Index, {
+        0, 1, 2
+    });
+
+    uint32_t zeroOffset = 0;
+    nxt::CommandBuffer commands = device.CreateCommandBufferBuilder()
+        .BeginRenderPass(renderpass, framebuffer)
+        .BeginRenderSubpass()
+            .SetIndexBuffer(indexBuffer, 0)
+            .SetRenderPipeline(pipeline)
+            .SetVertexBuffers(0, 1, &vertexBuffer, &zeroOffset)
+            .DrawElements(3, 1, 0, 0)
+        .EndRenderSubpass()
+        .EndRenderPass()
+        .GetResult();
+
+    queue.Submit(1, &commands);
+
+    EXPECT_PIXEL_RGBA8_EQ(RGBA8(0, 255, 0, 255), renderTarget, 100, 300);
+}
+
+NXT_INSTANTIATE_TEST(IndexFormatTest, MetalBackend, OpenGLBackend, VulkanBackend)