1) I know that auto-vectorization is done on GIMPLE. I think I need to understand entire syntax GIMPLE to understand internal files of gcc which does auto-vectorization like tree-vectorizer.c. Isn't it? 2)Where can I get complete syntax of GIMPLE? 3) Is it possible to compile a .gimple/.ssa/.rtl file? Actually I want to modify above representations of a .c program and compile the modified file. If it is possible tell me how to do? Thanks in advance. ___________________________________________________________ Inbox full of unwanted email? Get leading protection and 1GB storage with All New Yahoo! Mail. http://uk.docs.yahoo.com/nowyoucan.html