WIP rough sketch of vulkan backend structure.

src/xenia/gpu/vulkan/buffer_cache.h

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+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2016 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_GPU_VULKAN_BUFFER_CACHE_H_
+#define XENIA_GPU_VULKAN_BUFFER_CACHE_H_
+
+#include "xenia/gpu/register_file.h"
+#include "xenia/gpu/shader.h"
+#include "xenia/gpu/xenos.h"
+#include "xenia/ui/vulkan/vulkan.h"
+#include "xenia/ui/vulkan/vulkan_device.h"
+
+namespace xe {
+namespace gpu {
+namespace vulkan {
+
+// Efficiently manages buffers of various kinds.
+// Used primarily for uploading index and vertex data from guest memory and
+// transient data like shader constants.
+class BufferCache {
+ public:
+  BufferCache(RegisterFile* register_file, ui::vulkan::VulkanDevice* device,
+              size_t capacity);
+  ~BufferCache();
+
+  // Descriptor set containing the dynamic uniform buffer used for constant
+  // uploads. Used in conjunction with a dynamic offset returned by
+  // UploadConstantRegisters.
+  // The set contains two bindings:
+  //   binding = 0: for use in vertex shaders
+  //   binding = 1: for use in fragment shaders
+  VkDescriptorSet constant_descriptor_set() const {
+    return transient_descriptor_set_;
+  }
+
+  // Uploads the constants specified in the register maps to the transient
+  // uniform storage buffer.
+  // The registers are tightly packed in order as [floats, ints, bools].
+  // Returns an offset that can be used with the transient_descriptor_set or
+  // VK_WHOLE_SIZE if the constants could not be uploaded (OOM).
+  VkDeviceSize UploadConstantRegisters(
+      const Shader::ConstantRegisterMap& constant_register_map);
+
+  // Uploads index buffer data from guest memory, possibly eliding with
+  // recently uploaded data or cached copies.
+  // Returns a buffer and offset that can be used with vkCmdBindIndexBuffer.
+  // Size will be VK_WHOLE_SIZE if the data could not be uploaded (OOM).
+  std::pair<VkBuffer, VkDeviceSize> UploadIndexBuffer(const void* source_ptr,
+                                                      size_t source_length,
+                                                      IndexFormat format);
+
+  // Uploads vertex buffer data from guest memory, possibly eliding with
+  // recently uploaded data or cached copies.
+  // Returns a buffer and offset that can be used with vkCmdBindVertexBuffers.
+  // Size will be VK_WHOLE_SIZE if the data could not be uploaded (OOM).
+  std::pair<VkBuffer, VkDeviceSize> UploadVertexBuffer(const void* source_ptr,
+                                                       size_t source_length);
+
+  // Flushes all pending data to the GPU.
+  // Until this is called the GPU is not guaranteed to see any data.
+  // The given command buffer will be used to queue up events so that the
+  // cache can determine when data has been consumed.
+  void Flush(VkCommandBuffer command_buffer);
+
+  // Marks the cache as potentially invalid.
+  // This is not as strong as ClearCache and is a hint that any and all data
+  // should be verified before being reused.
+  void InvalidateCache();
+
+  // Clears all cached content and prevents future elision with pending data.
+  void ClearCache();
+
+ private:
+  // Allocates a block of memory in the transient buffer.
+  // Returns VK_WHOLE_SIZE if requested amount of memory is not available.
+  VkDeviceSize AllocateTransientData(size_t alignment, size_t length);
+
+  RegisterFile* register_file_ = nullptr;
+  VkDevice device_ = nullptr;
+
+  // Staging ringbuffer we cycle through fast. Used for data we don't
+  // plan on keeping past the current frame.
+  size_t transient_capacity_ = 0;
+  VkBuffer transient_uniform_buffer_ = nullptr;
+  VkBuffer transient_index_buffer_ = nullptr;
+  VkBuffer transient_vertex_buffer_ = nullptr;
+  VkDeviceMemory transient_buffer_memory_ = nullptr;
+  void* transient_buffer_data_ = nullptr;
+
+  // Required alignemnts for our various types.
+  // All allocations must start at the appropriate alignment.
+  VkDeviceSize uniform_buffer_alignment_ = 0;
+  VkDeviceSize index_buffer_alignment_ = 0;
+  VkDeviceSize vertex_buffer_alignment_ = 0;
+
+  VkDescriptorPool descriptor_pool_ = nullptr;
+  VkDescriptorSetLayout descriptor_set_layout_ = nullptr;
+  VkDescriptorSet transient_descriptor_set_ = nullptr;
+};
+
+}  // namespace vulkan
+}  // namespace gpu
+}  // namespace xe
+
+#endif  // XENIA_GPU_VULKAN_BUFFER_CACHE_H_