[d3d11] Chjeck whether input layouts are identical

Prevents redundant state changes when a game switches between
identical input layouts. Reduces the the number of Vulkan
calls in Grim Dawn by ~30%.

src/d3d11/d3d11_context.cpp

@@ -1235,7 +1235,17 @@ namespace dxvk {
     auto inputLayout = static_cast<D3D11InputLayout*>(pInputLayout);
     
     if (m_state.ia.inputLayout != inputLayout) {
+      bool equal = false;
+      
+      // Some games (e.g. Grim Dawn) create lots and lots of
+      // identical input layouts, so we'll only apply the state
+      // if the input layouts has actually changed between calls.
+      if (m_state.ia.inputLayout != nullptr && inputLayout != nullptr)
+        equal = m_state.ia.inputLayout->Compare(inputLayout);
+      
       m_state.ia.inputLayout = inputLayout;
+      
+      if (!equal)
         ApplyInputLayout();
     }
   }

src/d3d11/d3d11_input_layout.cpp

@@ -55,4 +55,25 @@ namespace dxvk {
       m_bindings.data());
   }
   
+  
+  bool D3D11InputLayout::Compare(const D3D11InputLayout* pOther) const {
+    bool eq = m_attributes.size() == pOther->m_attributes.size()
+           && m_bindings.size()   == pOther->m_bindings.size();
+    
+    for (uint32_t i = 0; eq && i < m_attributes.size(); i++) {
+      eq &= m_attributes[i].location == pOther->m_attributes[i].location
+         && m_attributes[i].binding  == pOther->m_attributes[i].binding
+         && m_attributes[i].format   == pOther->m_attributes[i].format
+         && m_attributes[i].offset   == pOther->m_attributes[i].offset;
+    }
+    
+    for (uint32_t i = 0; eq && i < m_bindings.size(); i++) {
+      eq &= m_bindings[i].binding    == pOther->m_bindings[i].binding
+         && m_bindings[i].fetchRate  == pOther->m_bindings[i].fetchRate
+         && m_bindings[i].inputRate  == pOther->m_bindings[i].inputRate;
+    }
+    
+    return eq;
+  }
+  
 }

src/d3d11/d3d11_input_layout.h

@@ -29,6 +29,9 @@ namespace dxvk {
     void BindToContext(
       const Rc<DxvkContext>&      ctx);
     
+    bool Compare(
+      const D3D11InputLayout*     pOther) const;
+    
   private:
     
     Com<D3D11Device> m_device;