DirectX using C++_error X3539:ps1_x is no longer supported...解决方案

PixelShader = compile ps_1_1 PS();

//create pixel shader
ID3DXBuffer* codeBuffer        = 0;
ID3DXBuffer* errorBuffer       = 0;
HRESULT hr = D3DXCompileShaderFromFile("ps.txt",
                                       0,
                                       0,
                                       "PS_Main", // entry point function name
                                       "ps_2_0",  //ps_1_1 is error X3539
                                       D3DXSHADER_DEBUG,
                                       &codeBuffer,
                                       &errorBuffer,
                                       &pixelConstTable);