[d3d11] Ignore explicit flush if there are unresolved render targets

Cursed perf hack for some Unity Engine games.

src/d3d11/d3d11_context_imm.cpp

@@ -156,6 +156,7 @@ namespace dxvk {
   void STDMETHODCALLTYPE D3D11ImmediateContext::Flush() {
     D3D10DeviceLock lock = LockContext();
 
+    if (!IgnoreExplicitFlush())
       ExecuteFlush(GpuFlushType::ExplicitFlush, nullptr, true);
   }
 
@@ -165,6 +166,7 @@ namespace dxvk {
           HANDLE                      hEvent) {
     D3D10DeviceLock lock = LockContext();
 
+    if (!IgnoreExplicitFlush())
       ExecuteFlush(GpuFlushType::ExplicitFlush, hEvent, true);
   }
   
@@ -1078,6 +1080,22 @@ namespace dxvk {
   }
 
 
+  bool D3D11ImmediateContext::IgnoreExplicitFlush() {
+    // This is sketchy in general since not respecting an explicit flush can
+    // keep resources alive indefinitely when they shouldn't be. Only do this
+    // in tiler mode if flushing would prevent resolve optimizations, and if
+    // we don't break submission order w.r.t. other D3D devices.
+    if (!m_device->perfHints().preferRenderPassOps)
+      return false;
+
+    if (m_parent->Is11on12Device()
+     || m_parent->HasSharedResources())
+      return false;
+
+    return m_hasPendingMsaaResolve;
+  }
+
+
   GpuFlushType D3D11ImmediateContext::GetMaxFlushType(
           D3D11Device*    pParent,
     const Rc<DxvkDevice>& Device) {

src/d3d11/d3d11_context_imm.h

@@ -210,6 +210,8 @@ namespace dxvk {
 
     DxvkStagingBufferStats GetStagingMemoryStatistics();
 
+    bool IgnoreExplicitFlush();
+
     static GpuFlushType GetMaxFlushType(
             D3D11Device*    pParent,
       const Rc<DxvkDevice>& Device);

src/d3d11/d3d11_device.cpp

@@ -2375,6 +2375,8 @@ namespace dxvk {
       Logger::err(e.message());
       return E_INVALIDARG;
     }
+
+    m_hasSharedResources.store(true, std::memory_order_release);
 #else
     Logger::warn("D3D11Device::OpenSharedResourceGeneric: Not supported on this platform.");
     return E_INVALIDARG;

src/d3d11/d3d11_device.h

@@ -464,6 +464,10 @@ namespace dxvk {
 
     bool Is11on12Device() const;
 
+    bool HasSharedResources() const {
+      return m_hasSharedResources.load(std::memory_order_acquire);
+    }
+
     static D3D_FEATURE_LEVEL GetMaxFeatureLevel(
       const Rc<DxvkInstance>& Instance,
       const Rc<DxvkAdapter>&  Adapter);
@@ -512,6 +516,8 @@ namespace dxvk {
     D3D_FEATURE_LEVEL               m_maxFeatureLevel;
     D3D11DeviceFeatures             m_deviceFeatures;
 
+    std::atomic<bool>               m_hasSharedResources = { false };
+
     HRESULT CreateShaderModule(
             D3D11CommonShader*      pShaderModule,
             DxvkShaderKey           ShaderKey,