Vulkan: Add read dependency for push constants fallback

When a shader uses push constants fallback the push constants are
stored inside a uniform buffer. The uniform buffer needs to be guarded
with a read barrier.

Pull Request: https://projects.blender.org/blender/blender/pulls/123777

source/blender/gpu/vulkan/vk_context.cc

@@ -255,6 +255,15 @@ void VKContext::update_pipeline_data(VKShader &vk_shader,
     r_pipeline_data.push_constants_data = vk_shader.push_constants.data();
   }
 
+  /* When using the push constant fallback we need to add a read access dependency to the uniform
+   * buffer after the buffer has been updated.
+   * NOTE: this alters the context instance variable `access_info_` which isn't clear from the API.
+   */
+  if (push_constants_layout.storage_type_get() == VKPushConstants::StorageType::UNIFORM_BUFFER) {
+    access_info_.buffers.append(
+        {vk_shader.push_constants.uniform_buffer_get()->vk_handle(), VK_ACCESS_UNIFORM_READ_BIT});
+  }
+
   /* Update descriptor set. */
   r_pipeline_data.vk_descriptor_set = VK_NULL_HANDLE;
   if (vk_shader.has_descriptor_set()) {

source/blender/gpu/vulkan/vk_push_constants.hh

@@ -46,6 +46,8 @@ class VKDevice;
  * data.
  */
 class VKPushConstants : VKResourceTracker<VKUniformBuffer> {
+  friend class VKContext;
+
  public:
   /** Different methods to store push constants. */
   enum class StorageType {