[dxvk] Add spec constants for pixel shader output mapping

src/dxvk/dxvk_graphics.cpp

@@ -237,6 +237,11 @@ namespace dxvk {
       omBlendAttachments[i].colorWriteMask = util::remapComponentMask(
         state.omBlendAttachments[i].colorWriteMask,
         state.omComponentMapping[i]);
+      
+      specData.outputMappings[4 * i + 0] = util::getComponentIndex(state.omComponentMapping[i].r, 0);
+      specData.outputMappings[4 * i + 1] = util::getComponentIndex(state.omComponentMapping[i].g, 1);
+      specData.outputMappings[4 * i + 2] = util::getComponentIndex(state.omComponentMapping[i].b, 2);
+      specData.outputMappings[4 * i + 3] = util::getComponentIndex(state.omComponentMapping[i].a, 3);
     }
 
     // Generate per-instance attribute divisors

src/dxvk/dxvk_shader.h

@@ -21,7 +21,12 @@ namespace dxvk {
    */
   enum class DxvkSpecConstantId : uint32_t {
     RasterizerSampleCount       = 0x10000,
-    
+
+    /// Special constant ranges that do not count
+    /// towards the spec constant min/max values
+    ColorComponentMappings      = 0x20000,
+
+    /// Lowest and highest known spec constant IDs
     SpecConstantIdMin           = RasterizerSampleCount,
     SpecConstantIdMax           = RasterizerSampleCount,
   };

src/dxvk/dxvk_spec_const.cpp

@@ -11,9 +11,12 @@ namespace dxvk {
   
   DxvkSpecConstantMap::DxvkSpecConstantMap() {
     SET_CONSTANT_ENTRY(DxvkSpecConstantId::RasterizerSampleCount, rasterizerSampleCount);
-    
+
     for (uint32_t i = 0; i < MaxNumActiveBindings; i++)
       this->setBindingEntry(i);
+    
+    for (uint32_t i = 0; i < MaxNumRenderTargets; i++)
+      this->setOutputMappingEntry(i);
   }
   
   
@@ -27,8 +30,8 @@ namespace dxvk {
     entry.size       = size;
     m_mapEntries[uint32_t(specId) - uint32_t(DxvkSpecConstantId::SpecConstantIdMin)] = entry;
   }
-  
+
-  
+
   void DxvkSpecConstantMap::setBindingEntry(
           uint32_t            binding) {
     VkSpecializationMapEntry entry;
@@ -37,5 +40,19 @@ namespace dxvk {
     entry.size       = sizeof(VkBool32);
     m_mapEntries[MaxNumSpecConstants + binding] = entry;
   }
+
+
+  void DxvkSpecConstantMap::setOutputMappingEntry(
+          uint32_t            output) {
+    for (uint32_t i = 0; i < 4; i++) {
+      uint32_t constId = 4 * output + i;
+
+      VkSpecializationMapEntry entry;
+      entry.constantID = uint32_t(DxvkSpecConstantId::ColorComponentMappings) + constId;
+      entry.offset     = sizeof(uint32_t) * constId + offsetof(DxvkSpecConstantData, outputMappings);
+      entry.size       = sizeof(uint32_t);
+      m_mapEntries[MaxNumSpecConstants + MaxNumActiveBindings + constId] = entry;
+    }
+  }
   
 }

src/dxvk/dxvk_spec_const.h

@@ -18,6 +18,7 @@ namespace dxvk {
    */
   struct DxvkSpecConstantData {
     uint32_t rasterizerSampleCount;
+    uint32_t outputMappings[MaxNumRenderTargets * 4];
     VkBool32 activeBindings[MaxNumActiveBindings];
   };
   
@@ -55,7 +56,10 @@ namespace dxvk {
     
   private:
     
-    std::array<VkSpecializationMapEntry, MaxNumSpecConstants + MaxNumActiveBindings> m_mapEntries;
+    std::array<VkSpecializationMapEntry,
+      MaxNumSpecConstants  +
+      MaxNumActiveBindings +
+      MaxNumRenderTargets * 4> m_mapEntries;
     
     void setConstantEntry(
             DxvkSpecConstantId  specId,
@@ -65,6 +69,9 @@ namespace dxvk {
     void setBindingEntry(
             uint32_t            binding);
     
+    void setOutputMappingEntry(
+            uint32_t            output);
+    
   };
   
   extern DxvkSpecConstantMap g_specConstantMap;

src/dxvk/dxvk_util.cpp

@@ -136,4 +136,17 @@ namespace dxvk::util {
     return result;
   }
 
+
+  uint32_t getComponentIndex(
+          VkComponentSwizzle          component,
+          uint32_t                    identity) {
+    switch (component) {
+      case VK_COMPONENT_SWIZZLE_R: return 0;
+      case VK_COMPONENT_SWIZZLE_G: return 1;
+      case VK_COMPONENT_SWIZZLE_B: return 2;
+      case VK_COMPONENT_SWIZZLE_A: return 3;
+      default: return identity; /* identity, zero, one */
+    }
+  }
+
 }

src/dxvk/dxvk_util.h

@@ -201,6 +201,17 @@ namespace dxvk::util {
   VkComponentMapping invertComponentMapping(
           VkComponentMapping          mapping);
   
+  /**
+   * \brief Computes component index for a component swizzle
+   * 
+   * \param [in] component The component swizzle
+   * \param [in] identity Value for SWIZZLE_IDENTITY
+   * \returns Component index
+   */
+  uint32_t getComponentIndex(
+          VkComponentSwizzle          component,
+          uint32_t                    identity);
+  
 }