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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) 1998-2017 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.
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