The standard defines exactly where they occur. The option of marking these in the SUIF code is provided in case later passes want to use them to print traces of variable values or something of that sort. This is the default. If a NULL pointer is found, an error message is issued giving the source line number and file and the program aborts. This is the default.
Target information is stored in the snoot source file config .
When more changes were made to SUIF that required more information to be preserved that lcc was losing early-on, Chris Wilson rewrote snoot . Various internal transformations and datastructures used by lcc were removed. Now the front-end of lcc is used to generate SUIF code directly.