From 0369d9b2cbe9491b7e75615dfb21ac92786f5431 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Fri, 8 Aug 2025 11:03:03 +0200
Subject: [PATCH] Optimize `CSSetShader` on D3D11 when remains unchanged

---
 .../DirectX/DX11/GPUContextDX11.cpp               | 15 +++++++++++++--
 .../GraphicsDevice/DirectX/DX11/GPUContextDX11.h  |  1 +
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.cpp b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.cpp
index b68f5e595..62f9afd3a 100644
--- a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.cpp
+++ b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.cpp
@@ -95,6 +95,7 @@ void GPUContextDX11::FrameBegin()
     _srMaskDirtyCompute = 0;
     _rtCount = 0;
     _vertexLayout = nullptr;
+    _currentCompute = nullptr;
     _currentState = nullptr;
     _rtDepth = nullptr;
     Platform::MemoryClear(_rtHandles, sizeof(_rtHandles));
@@ -497,7 +498,12 @@ void GPUContextDX11::Dispatch(GPUShaderProgramCS* shader, uint32 threadGroupCoun
     flushOM();
 
     // Dispatch
-    _context->CSSetShader((ID3D11ComputeShader*)shader->GetBufferHandle(), nullptr, 0);
+    auto compute = (ID3D11ComputeShader*)shader->GetBufferHandle();
+    if (_currentCompute != compute)
+    {
+        _currentCompute = compute;
+        _context->CSSetShader(compute, nullptr, 0);
+    }
     _context->Dispatch(threadGroupCountX, threadGroupCountY, threadGroupCountZ);
     RENDER_STAT_DISPATCH_CALL();
 
@@ -518,7 +524,12 @@ void GPUContextDX11::DispatchIndirect(GPUShaderProgramCS* shader, GPUBuffer* buf
     flushOM();
 
     // Dispatch
-    _context->CSSetShader((ID3D11ComputeShader*)shader->GetBufferHandle(), nullptr, 0);
+    auto compute = (ID3D11ComputeShader*)shader->GetBufferHandle();
+    if (_currentCompute != compute)
+    {
+        _currentCompute = compute;
+        _context->CSSetShader(compute, nullptr, 0);
+    }
     _context->DispatchIndirect(bufferForArgsDX11->GetBuffer(), offsetForArgs);
     RENDER_STAT_DISPATCH_CALL();
 
diff --git a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.h b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.h
index 48de69b3f..6d1877534 100644
--- a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.h
+++ b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUContextDX11.h
@@ -59,6 +59,7 @@ private:
     bool _iaInputLayoutDirtyFlag;
 
     // Pipeline State
+    ID3D11ComputeShader* _currentCompute;
     GPUPipelineStateDX11* _currentState;
     ID3D11BlendState* CurrentBlendState;
     ID3D11RasterizerState* CurrentRasterizerState;