LANGUAGES revision 50397 
1Right now there is no documentation for the GCC tree -> rtl interfaces
2(or more generally the interfaces for adding new languages).
3
4Such documentation would be of great benefit to the project.  Until such
5time as we can formally start documenting the interface this file will
6serve as a repository for information on these interface and any incompatable
7changes we've made.
8
9Jun 10, 1998:
10  The interface to lang_decode_option has changed. It now uses and argc/argv
11  interface to allow for options that use more than one input string. The new
12  declaration is: int lang_decode_option (int argc, char** argv). It now
13  returns the number of input strings processed, or 0 if the option is
14  unknown.
15
16Jun  7, 1998:
17  Front-ends must now define lang_init_options.  It is safe for this
18  function to do nothing.  See c-lang.c.
19
20Apr 21, 1998:
21  Front ends which link with c-common or other files from the C/C++
22  front-ends may need to handle TI types.  Look for references to
23  [unsigned]int_DI_type_node in your front end.  If you have references
24  to these variables, you'll need up update the front end.
25
26  To update the front end you must mirror all the code which currently
27  deals with intDI_type_node to also handle intTI_type_node.
28
29
30Apr 7, 1998:
31  The interface between toplev.c and the language front ends for opening the
32  source file has changed:
33
34  o init_lex() has been renamed to init_parse (char *filename) where filename
35    is the name of the source file.
36  o The code in toplev.c which opened the source file should be moved to
37    the new init_parse function.
38  o toplev.c now calls finish_parse() instead of closing the source file
39    using fclose(). This should now be done in finish_parse, if necessary.
40
41Apr 1, 1998:
42  Front-ends must now define lang_print_xnode.  It is safe for this
43  function to do nothing.  See c-lang.c.
44
45Feb 1, 1998:
46
47  GCC used to store structure sizes & offsets to elements as bitsize
48  quantities.  This causes problems because a structure can only be
49  (target memsize / 8) bytes long (this may effect arrays too).  This
50  is particularly problematical on machines with small address spaces.
51
52  So:
53
54    All trees that represent sizes in bits should have a TREE_TYPE of
55    bitsizetype (rather than sizetype).
56
57    Accordingly, when such values are computed / initialized, care has to
58    be takes to use / compute the proper type.
59
60    When a size in bits is converted into a size in bytes, which is expressed
61    in trees, care should be taken to change the tree's type again to sizetype.
62
63    We've updated C, C++, Fortran & Objective-C to work with the new
64    scheme.  Other languages will need to be updated accordingly.
65    Contact amylaar@cygnus.com for additional information.
66
67?? 1997:
68
69  In an effort to decrease cache thrashing and useless loads we've changed the
70  third argument to the DEFTREECODE macro to be a single char.  This will
71  effect languages that defined their own tree codes (usually in a .def file).
72
73  Old way:
74
75    DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", "d", 0)
76
77  New way:
78
79    DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
80