row_major float4x4 mWorldViewProj;
//
float3 pos=mul(mWorldViewProj,vPosition);
对应指令为：

dp3 oPos.x, c0, v0  
dp3 oPos.y, c1, v0  
dp3 oPos.z, c2, v0  











column_major float4x4 mWorldViewProj;
//
float3 pos=mul(vPosition，mWorldViewProj);
对应指令为：

dp3 oPos.x, v0, c0  
dp3 oPos.y, v0, c1  
dp3 oPos.z, v0, c2   
原因是：
对于mul指令
Performs matrix multiplication between x and y. 
If x is a vector, it treated as a row vector. 
If y is a vector, it is treated as a column vector.