gcc/doc/gccint/rtl-representation/reading-rtl.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. _reading-rtl:
   7
   8 Reading RTL
   9 ***********
  10
  11 To read an RTL object from a file, call ``read_rtx``.  It takes one
  12 argument, a stdio stream, and returns a single RTL object.  This routine
  13 is defined in :samp:`read-rtl.cc`.  It is not available in the compiler
  14 itself, only the various programs that generate the compiler back end
  15 from the machine description.
  16
  17 People frequently have the idea of using RTL stored as text in a file as
  18 an interface between a language front end and the bulk of GCC.  This
  19 idea is not feasible.
  20
  21 GCC was designed to use RTL internally only.  Correct RTL for a given
  22 program is very dependent on the particular target machine.  And the RTL
  23 does not contain all the information about the program.
  24
  25 The proper way to interface GCC to a new language front end is with
  26 the 'tree' data structure, described in the files :samp:`tree.h` and
  27 :samp:`tree.def`.  The documentation for this structure (see :ref:`generic`)
  28 is incomplete.