19.20 Reading RTL

To read an RTL object from a file, call read_rtx. It takes one argument, a stdio stream, and returns a single RTL object.

Reading RTL from a file is very slow. This is not currently a problem since reading RTL occurs only as part of building the compiler.

People frequently have the idea of using RTL stored as text in a file as an interface between a language front end and the bulk of GNU CC. This idea is not feasible.

GNU CC was designed to use RTL internally only. Correct RTL for a given program is very dependent on the particular target machine. And the RTL does not contain all the information about the program.

The proper way to interface GNU CC to a new language front end is with the "tree" data structure, described in the files `tree.h' and `tree.def'. The documentation for this structure (see section 18. Trees: The intermediate representation used by the C and C++ front-ends) is incomplete.