Thanks for the help. I guess I just had a hard time understanding how gcc creates trees for constants. Now I have everything working. I just wanted to know how I could test vector_cst. I tried: typedef short someType __attribute__((vector_size(8))); someType someName = {1,-1}; But it produces a Constructor with vector type instead. What is the right way to produce a vector_cst? Thanks once again and Happy new year! Primrose