Revert "[dxbc] Do not emit per-vertex input block"

This reverts commit 4ce64bd8865bbb25baa25d622437c9258126c4d2.

Fixes a regression in Sniper: Ghost Warrior 2 and Dishonored 2.

src/dxbc/dxbc_compiler.cpp

@@ -588,9 +588,6 @@ namespace dxvk {
       bool skipSv = sv == DxbcSystemValue::ClipDistance
                  || sv == DxbcSystemValue::CullDistance;
       
-      if (m_version.type() != DxbcProgramType::PixelShader)
-        skipSv = skipSv || sv == DxbcSystemValue::Position;
-      
       if (!skipSv)
         m_vMappings.push_back({ regIdx, regMask, sv });
     }
@@ -1083,7 +1080,11 @@ namespace dxvk {
     m_gs.inputPrimitive = ins.controls.primitive;
     m_module.setExecutionMode(m_entryPointId, mode);
     
-    emitDclInputArray(primitiveVertexCount(m_gs.inputPrimitive));
+    const uint32_t vertexCount
+      = primitiveVertexCount(m_gs.inputPrimitive);
+    
+    emitDclInputArray(vertexCount);
+    emitDclInputPerVertex(vertexCount, "gs_vertex_in");
   }
   
   
@@ -4929,9 +4930,34 @@ namespace dxvk {
           DxbcSystemValue         sv,
           DxbcRegMask             mask,
           uint32_t                vertexId) {
+    switch (sv) {
+      case DxbcSystemValue::Position: {
+        const std::array<uint32_t, 2> indices = {
+          m_module.consti32(vertexId),
+          m_module.consti32(PerVertex_Position),
+        };
+        
+        DxbcRegisterPointer ptrIn;
+        ptrIn.type.ctype  = DxbcScalarType::Float32;
+        ptrIn.type.ccount = 4;
+        
+        ptrIn.id = m_module.opAccessChain(
+          m_module.defPointerType(
+            getVectorTypeId(ptrIn.type),
+            spv::StorageClassInput),
+          m_perVertexIn,
+          indices.size(),
+          indices.data());
+        
+        return emitRegisterExtract(
+          emitValueLoad(ptrIn), mask);
+      } break;
+      
+      default:
         throw DxvkError(str::format(
           "DxbcCompiler: Unhandled GS SV input: ", sv));
     }
+  }
   
   
   DxbcRegisterValue DxbcCompiler::emitPsSystemValueLoad(
@@ -5672,6 +5698,25 @@ namespace dxvk {
   }
   
   
+  void DxbcCompiler::emitDclInputPerVertex(
+          uint32_t          vertexCount,
+    const char*             varName) {
+    uint32_t typeId = getPerVertexBlockId();
+    
+    if (vertexCount != 0) {
+      typeId = m_module.defArrayType(typeId,
+        m_module.constu32(vertexCount));
+    }
+    
+    const uint32_t ptrTypeId = m_module.defPointerType(
+      typeId, spv::StorageClassInput);
+    
+    m_perVertexIn = m_module.newVar(
+      ptrTypeId, spv::StorageClassInput);
+    m_module.setDebugName(m_perVertexIn, varName);
+  }
+  
+  
   uint32_t DxbcCompiler::emitDclClipCullDistanceArray(
           uint32_t          length,
           spv::BuiltIn      builtIn,

src/dxbc/dxbc_compiler.h

@@ -390,6 +390,7 @@ namespace dxvk {
     ////////////////////////////////////////////////////
     // Per-vertex input and output blocks. Depending on
     // the shader stage, these may be declared as arrays.
+    uint32_t m_perVertexIn  = 0;
     uint32_t m_perVertexOut = 0;
     
     uint32_t m_clipDistances = 0;
@@ -943,6 +944,10 @@ namespace dxvk {
     void emitDclInputArray(
             uint32_t          vertexCount);
     
+    void emitDclInputPerVertex(
+            uint32_t          vertexCount,
+      const char*             varName);
+    
     uint32_t emitDclClipCullDistanceArray(
             uint32_t          length,
             spv::BuiltIn      builtIn,