[d3d11] Revert index buffer optimization

This causes some problems when the app uses a combination of index
buffer offset and StartIndexLocation that overflows 32-bit integers.

In my testing, there haven't been many games benefitting from this
optimization anyway, so just reverting it should not have tangible
effects on performance.

src/d3d11/d3d11_context.cpp

@@ -1465,7 +1465,6 @@ namespace dxvk {
           UINT            StartIndexLocation,
           INT             BaseVertexLocation) {
     D3D10DeviceLock lock = LockContext();
-    StartIndexLocation += m_state.ia.indexBuffer.firstIndex;
     
     EmitCs([=] (DxvkContext* ctx) {
       ctx->drawIndexed(
@@ -1500,7 +1499,6 @@ namespace dxvk {
           INT             BaseVertexLocation,
           UINT            StartInstanceLocation) {
     D3D10DeviceLock lock = LockContext();
-    StartIndexLocation += m_state.ia.indexBuffer.firstIndex;
     
     EmitCs([=] (DxvkContext* ctx) {
       ctx->drawIndexed(
@@ -1675,12 +1673,6 @@ namespace dxvk {
     if (needsUpdate)
       m_state.ia.indexBuffer.buffer = newBuffer;
 
-    if (likely(m_state.ia.indexBuffer.optimized)) {
-      uint32_t shift = Format == DXGI_FORMAT_R16_UINT ? 1 : 2;
-      m_state.ia.indexBuffer.firstIndex = Offset >> shift;
-      Offset = 0;
-    }
-
     needsUpdate |= m_state.ia.indexBuffer.offset != Offset
                 || m_state.ia.indexBuffer.format != Format;
 
@@ -1740,12 +1732,8 @@ namespace dxvk {
     if (pFormat != nullptr)
       *pFormat = m_state.ia.indexBuffer.format;
     
-    if (pOffset != nullptr) {
+    if (pOffset != nullptr)
-      uint32_t shift = m_state.ia.indexBuffer.format == DXGI_FORMAT_R16_UINT ? 1 : 2;
+      *pOffset = m_state.ia.indexBuffer.offset;
-      *pOffset = m_state.ia.indexBuffer.optimized
-        ? m_state.ia.indexBuffer.firstIndex << shift
-        : m_state.ia.indexBuffer.offset;
-    }
   }
   
   
@@ -3401,13 +3389,7 @@ namespace dxvk {
 
   void D3D11DeviceContext::BindFramebuffer() {
     DxvkRenderTargets attachments;
-
+    
-    // Re-enable index buffer optimization here. Some games will
-    // use indirect draws for actual scene rendering, but then
-    // use direct draws for things like the user interface.
-    if (!m_state.ia.indexBuffer.optimized)
-      SetIndexBufferOptimized(true);
-
     // D3D11 doesn't have the concept of a framebuffer object,
     // so we'll just create a new one every time the render
     // target bindings are updated. Set up the attachments.
@@ -3602,39 +3584,12 @@ namespace dxvk {
   }
 
 
-  void D3D11DeviceContext::SetIndexBufferOptimized(
-          BOOL                              Enable) {
-    uint32_t shift = m_state.ia.indexBuffer.format == DXGI_FORMAT_R16_UINT ? 1 : 2;
-
-    if (Enable) {
-      m_state.ia.indexBuffer.firstIndex = m_state.ia.indexBuffer.offset >> shift;
-      m_state.ia.indexBuffer.offset = 0;
-    } else {
-      m_state.ia.indexBuffer.offset += m_state.ia.indexBuffer.firstIndex << shift;
-      m_state.ia.indexBuffer.firstIndex = 0;
-    }
-
-    m_state.ia.indexBuffer.optimized = Enable;
-
-    BindIndexBuffer(
-      m_state.ia.indexBuffer.buffer.ptr(),
-      m_state.ia.indexBuffer.offset,
-      m_state.ia.indexBuffer.format);
-  }
-
-
   void D3D11DeviceContext::SetDrawBuffers(
           ID3D11Buffer*                     pBufferForArgs,
           ID3D11Buffer*                     pBufferForCount) {
     auto argBuffer = static_cast<D3D11Buffer*>(pBufferForArgs);
     auto cntBuffer = static_cast<D3D11Buffer*>(pBufferForCount);
 
-    // Bind index buffer with the actual offset since otherwise the
-    // first index members of the indirect draw structures would be
-    // incorrect.
-    if (unlikely(m_state.ia.indexBuffer.optimized))
-      SetIndexBufferOptimized(false);
-
     if (m_state.id.argBuffer != argBuffer
      || m_state.id.cntBuffer != cntBuffer) {
       m_state.id.argBuffer = argBuffer;

src/d3d11/d3d11_context.h

@@ -786,9 +786,6 @@ namespace dxvk {
             ID3D11Resource*                   pResource,
             UINT                              Subresource);
     
-    void SetIndexBufferOptimized(
-            BOOL                              Enable);
-    
     void SetDrawBuffers(
             ID3D11Buffer*                     pBufferForArgs,
             ID3D11Buffer*                     pBufferForCount);

src/d3d11/d3d11_context_state.h

@@ -103,8 +103,6 @@ namespace dxvk {
     Com<D3D11Buffer> buffer = nullptr;
     UINT             offset = 0;
     DXGI_FORMAT      format = DXGI_FORMAT_UNKNOWN;
-    UINT             firstIndex = 0;
-    BOOL             optimized  = true;
   };