From ebabc0e578e37ba4d33e2d73744c64905ae92431 Mon Sep 17 00:00:00 2001
From: Philip Rebohle <philip.rebohle@tu-dortmund.de>
Date: Sat, 16 Dec 2017 21:30:48 +0100
Subject: [PATCH] [dxvk] Implemented proper swap chain synchronization

---
 src/dxgi/dxgi_presenter.cpp | 16 +++++-----------
 src/dxgi/dxgi_presenter.h   |  3 ---
 src/dxvk/dxvk_swapchain.cpp | 13 +++++++++++++
 src/dxvk/dxvk_swapchain.h   | 33 +++++++++++++++++++++++++++++----
 4 files changed, 47 insertions(+), 18 deletions(-)

diff --git a/src/dxgi/dxgi_presenter.cpp b/src/dxgi/dxgi_presenter.cpp
index 23125f1d..b8800fb5 100644
--- a/src/dxgi/dxgi_presenter.cpp
+++ b/src/dxgi/dxgi_presenter.cpp
@@ -29,10 +29,6 @@ namespace dxvk {
     m_swapchain = m_device->createSwapchain(
       m_surface, swapchainProperties);
     
-    // Synchronization semaphores for swap chain operations
-    m_acquireSync = m_device->createSemaphore();
-    m_presentSync = m_device->createSemaphore();
-    
     // Sampler for presentation
     DxvkSamplerCreateInfo samplerInfo;
     samplerInfo.magFilter       = VK_FILTER_NEAREST;
@@ -172,7 +168,9 @@ namespace dxvk {
         m_backBuffer,        resolveSubresources);
     }
     
-    auto framebuffer     = m_swapchain->getFramebuffer(m_acquireSync);
+    const DxvkSwapSemaphores sem = m_swapchain->getSemaphorePair();
+    
+    auto framebuffer     = m_swapchain->getFramebuffer(sem.acquireSync);
     auto framebufferSize = framebuffer->size();
     
     m_context->bindFramebuffer(framebuffer);
@@ -203,13 +201,9 @@ namespace dxvk {
     
     m_device->submitCommandList(
       m_context->endRecording(),
-      m_acquireSync, m_presentSync);
+      sem.acquireSync, sem.presentSync);
     
-    m_swapchain->present(m_presentSync);
-    
-    // FIXME Make sure that the semaphores and the command
-    // list can be safely used without stalling the device.
-    m_device->waitForIdle();
+    m_swapchain->present(sem.presentSync);
   }
   
   
diff --git a/src/dxgi/dxgi_presenter.h b/src/dxgi/dxgi_presenter.h
index 7389d8b0..acb859ed 100644
--- a/src/dxgi/dxgi_presenter.h
+++ b/src/dxgi/dxgi_presenter.h
@@ -78,9 +78,6 @@ namespace dxvk {
     Rc<DxvkSurface>     m_surface;
     Rc<DxvkSwapchain>   m_swapchain;
     
-    Rc<DxvkSemaphore>   m_acquireSync;
-    Rc<DxvkSemaphore>   m_presentSync;
-    
     Rc<DxvkSampler>     m_sampler;
     
     Rc<DxvkImage>       m_backBuffer;
diff --git a/src/dxvk/dxvk_swapchain.cpp b/src/dxvk/dxvk_swapchain.cpp
index 581ffd21..ccacb6ec 100644
--- a/src/dxvk/dxvk_swapchain.cpp
+++ b/src/dxvk/dxvk_swapchain.cpp
@@ -26,6 +26,14 @@ namespace dxvk {
   }
   
   
+  DxvkSwapSemaphores DxvkSwapchain::getSemaphorePair() {
+    // It doesn't really matter that we increment the
+    // counter *before* returning the semaphore pair
+    m_frameIndex = (m_frameIndex + 1) % m_semaphoreSet.size();
+    return m_semaphoreSet.at(m_frameIndex);
+  }
+  
+  
   Rc<DxvkFramebuffer> DxvkSwapchain::getFramebuffer(
     const Rc<DxvkSemaphore>& wakeSync) {
     VkResult status = this->acquireNextImage(wakeSync);
@@ -131,7 +139,9 @@ namespace dxvk {
     
     // Retrieve swap images
     auto swapImages = this->retrieveSwapImages();
+    
     m_framebuffers.resize(swapImages.size());
+    m_semaphoreSet.resize(swapImages.size());
     
     DxvkImageCreateInfo imageInfo;
     imageInfo.type          = VK_IMAGE_TYPE_2D;
@@ -169,6 +179,9 @@ namespace dxvk {
       
       m_framebuffers.at(i) = new DxvkFramebuffer(
         m_vkd, m_renderPass, renderTargets);
+      
+      m_semaphoreSet.at(i).acquireSync = m_device->createSemaphore();
+      m_semaphoreSet.at(i).presentSync = m_device->createSemaphore();
     }
   }
   
diff --git a/src/dxvk/dxvk_swapchain.h b/src/dxvk/dxvk_swapchain.h
index a6c5984b..cb5ff103 100644
--- a/src/dxvk/dxvk_swapchain.h
+++ b/src/dxvk/dxvk_swapchain.h
@@ -10,7 +10,19 @@ namespace dxvk {
   class DxvkSurface;
   
   /**
-   * \brief 
+   * \brief Swap chain semaphore pair
+   * 
+   * Holds the two semaphores requires for
+   * synchronizing swap chain operations.
+   */
+  struct DxvkSwapSemaphores {
+    Rc<DxvkSemaphore> acquireSync; ///< Post-acquire semaphore
+    Rc<DxvkSemaphore> presentSync; ///< Pre-present semaphore
+  };
+  
+  
+  /**
+   * \brief Swap chain properties
    */
   struct DxvkSwapchainProperties {
     VkSurfaceFormatKHR preferredSurfaceFormat;
@@ -22,7 +34,9 @@ namespace dxvk {
   /**
    * \brief DXVK swapchain
    * 
-   * Manages a Vulkan swapchain object.
+   * Manages a Vulkan swap chain object. Implements
+   * acquire and present methods and recreates the
+   * underlying swap chain object as necessary.
    */
   class DxvkSwapchain : public RcObject {
     
@@ -34,6 +48,16 @@ namespace dxvk {
       const DxvkSwapchainProperties&  properties);
     ~DxvkSwapchain();
     
+    /**
+     * \brief Acquires a pair of semaphores
+     * 
+     * Retrieves a set of semaphores for the acquire
+     * and present operations. This must be called
+     * \e before \c getFramebuffer.
+     * \returns Semaphore pair
+     */
+    DxvkSwapSemaphores getSemaphorePair();
+    
     /**
      * \brief Retrieves the framebuffer for the current frame
      * 
@@ -78,8 +102,9 @@ namespace dxvk {
     uint32_t                m_imageIndex = 0;
     uint32_t                m_frameIndex = 0;
     
-    Rc<DxvkRenderPass>               m_renderPass;
-    std::vector<Rc<DxvkFramebuffer>> m_framebuffers;
+    Rc<DxvkRenderPass>                m_renderPass;
+    std::vector<Rc<DxvkFramebuffer>>  m_framebuffers;
+    std::vector<DxvkSwapSemaphores>   m_semaphoreSet;
     
     VkResult acquireNextImage(
       const Rc<DxvkSemaphore>& wakeSync);