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
92004-09-09:
10  In an effort to decrease execution time, single char tree code
11  classes were changed to enumerated values.
12
13  Old way:
14
15    DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
16
17  New way:
18
19    DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", tcc_declaration, 0)
20
212001-02-26:
22  A DECL_INITIAL of NULL_TREE or error_mark_node in a VAR_DECL is no longer
23  taken to signify a tentative definition which should not be emitted until
24  end-of-file.  Frontends which want that behavior should set
25  DECL_DEFER_OUTPUT before calling rest_of_decl_compilation.
26
27Feb 1, 1998:
28
29  GCC used to store structure sizes & offsets to elements as bitsize
30  quantities.  This causes problems because a structure can only be
31  (target memsize / 8) bytes long (this may effect arrays too).  This
32  is particularly problematical on machines with small address spaces.
33
34  So:
35
36    All trees that represent sizes in bits should have a TREE_TYPE of
37    bitsizetype (rather than sizetype).
38
39    Accordingly, when such values are computed / initialized, care has to
40    be takes to use / compute the proper type.
41
42    When a size in bits is converted into a size in bytes, which is expressed
43    in trees, care should be taken to change the tree's type again to sizetype.
44
45?? 1997:
46
47  In an effort to decrease cache thrashing and useless loads we've changed the
48  third argument to the DEFTREECODE macro to be a single char.  This will
49  affect languages that defined their own tree codes (usually in a .def file).
50
51  Old way:
52
53    DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", "d", 0)
54
55  New way:
56
57    DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
58