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+Right now there is no documentation for the GCC tree -> rtl interfaces
+(or more generally the interfaces for adding new languages).
+
+Such documentation would be of great benefit to the project. Until such
+time as we can formally start documenting the interface this file will
+serve as a repository for information on these interface and any incompatible
+changes we've made.
+
+2004-09-09:
+ In an effort to decrease execution time, single char tree code
+ classes were changed to enumerated values.
+
+ Old way:
+
+ DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
+
+ New way:
+
+ DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", tcc_declaration, 0)
+
+2001-02-26:
+ A DECL_INITIAL of NULL_TREE or error_mark_node in a VAR_DECL is no longer
+ taken to signify a tentative definition which should not be emitted until
+ end-of-file. Frontends which want that behavior should set
+ DECL_DEFER_OUTPUT before calling rest_of_decl_compilation.
+
+Feb 1, 1998:
+
+ GCC used to store structure sizes & offsets to elements as bitsize
+ quantities. This causes problems because a structure can only be
+ (target memsize / 8) bytes long (this may effect arrays too). This
+ is particularly problematical on machines with small address spaces.
+
+ So:
+
+ All trees that represent sizes in bits should have a TREE_TYPE of
+ bitsizetype (rather than sizetype).
+
+ Accordingly, when such values are computed / initialized, care has to
+ be takes to use / compute the proper type.
+
+ When a size in bits is converted into a size in bytes, which is expressed
+ in trees, care should be taken to change the tree's type again to sizetype.
+
+?? 1997:
+
+ In an effort to decrease cache thrashing and useless loads we've changed the
+ third argument to the DEFTREECODE macro to be a single char. This will
+ affect languages that defined their own tree codes (usually in a .def file).
+
+ Old way:
+
+ DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", "d", 0)
+
+ New way:
+
+ DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
+
+
+Copyright (C) 1998-2013 Free Software Foundation, Inc.
+
+Copying and distribution of this file, with or without modification,
+are permitted in any medium without royalty provided the copyright
+notice and this notice are preserved.