vk_rasterizer: Add lazy default buffer maker and use it for empty buffers

Introduce a default buffer getter that lazily constructs an empty
buffer. This is intended to match OpenGL's buffer 0.

Use this for disabled vertex and uniform buffers.

While we are at it, include vertex buffer usages for staging buffers to
silence validation errors.

1 files changed, 33 insertions, 3 deletions

diff --git a/src/video_core/renderer_vulkan/vk_rasterizer.cpp b/src/video_core/renderer_vulkan/vk_rasterizer.cpp
index 2ebf34fc4..538cf73a6 100644
--- a/src/video_core/renderer_vulkan/vk_rasterizer.cpp
+++ b/src/video_core/renderer_vulkan/vk_rasterizer.cpp
@@ -836,6 +836,10 @@ void RasterizerVulkan::SetupVertexArrays(FixedPipelineState::VertexInput& vertex
 
         ASSERT(end >= start);
         const std::size_t size{end - start};
+        if (size == 0) {
+            buffer_bindings.AddVertexBinding(DefaultBuffer(), 0);
+            continue;
+        }
         const auto [buffer, offset] = buffer_cache.UploadMemory(start, size);
         buffer_bindings.AddVertexBinding(buffer, offset);
     }
@@ -990,8 +994,7 @@ void RasterizerVulkan::SetupConstBuffer(const ConstBufferEntry& entry,
                                         const Tegra::Engines::ConstBufferInfo& buffer) {
     if (!buffer.enabled) {
         // Set values to zero to unbind buffers
-        update_descriptor_queue.AddBuffer(buffer_cache.GetEmptyBuffer(sizeof(float)), 0,
-                                          sizeof(float));
+        update_descriptor_queue.AddBuffer(DefaultBuffer(), 0, DEFAULT_BUFFER_SIZE);
         return;
     }
 
@@ -1014,7 +1017,9 @@ void RasterizerVulkan::SetupGlobalBuffer(const GlobalBufferEntry& entry, GPUVAdd
     if (size == 0) {
         // Sometimes global memory pointers don't have a proper size. Upload a dummy entry
         // because Vulkan doesn't like empty buffers.
-        constexpr std::size_t dummy_size = 4;
+        // Note: Do *not* use DefaultBuffer() here, storage buffers can be written breaking the
+        // default buffer.
+        static constexpr std::size_t dummy_size = 4;
         const auto buffer = buffer_cache.GetEmptyBuffer(dummy_size);
         update_descriptor_queue.AddBuffer(buffer, 0, dummy_size);
         return;
@@ -1226,4 +1231,29 @@ RenderPassParams RasterizerVulkan::GetRenderPassParams(Texceptions texceptions)
     return renderpass_params;
 }
 
+VkBuffer RasterizerVulkan::DefaultBuffer() {
+    if (default_buffer) {
+        return *default_buffer;
+    }
+
+    VkBufferCreateInfo ci;
+    ci.sType = VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO;
+    ci.pNext = nullptr;
+    ci.flags = 0;
+    ci.size = DEFAULT_BUFFER_SIZE;
+    ci.usage = VK_BUFFER_USAGE_TRANSFER_DST_BIT | VK_BUFFER_USAGE_VERTEX_BUFFER_BIT |
+               VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT;
+    ci.sharingMode = VK_SHARING_MODE_EXCLUSIVE;
+    ci.queueFamilyIndexCount = 0;
+    ci.pQueueFamilyIndices = nullptr;
+    default_buffer = device.GetLogical().CreateBuffer(ci);
+    default_buffer_commit = memory_manager.Commit(default_buffer, false);
+
+    scheduler.RequestOutsideRenderPassOperationContext();
+    scheduler.Record([buffer = *default_buffer](vk::CommandBuffer cmdbuf) {
+        cmdbuf.FillBuffer(buffer, 0, DEFAULT_BUFFER_SIZE, 0);
+    });
+    return *default_buffer;
+}
+
 } // namespace Vulkan