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98 lines
4.0 KiB
Plaintext
98 lines
4.0 KiB
Plaintext
Right now there is no documentation for the GCC tree -> rtl interfaces
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(or more generally the interfaces for adding new languages).
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Such documentation would be of great benefit to the project. Until such
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time as we can formally start documenting the interface this file will
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serve as a repository for information on these interface and any incompatable
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changes we've made.
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2001-02-26:
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A DECL_INITIAL of NULL_TREE or error_mark_node in a VAR_DECL is no longer
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taken to signify a tentative definition which should not be emitted until
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end-of-file. Frontends which want that behavior should set
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DECL_DEFER_OUTPUT before calling rest_of_decl_compilation.
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Aug 31, 1998:
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The interface to HANDLE_PRAGMA has changed. It now takes three arguments.
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The first two are pointers to functions that should be used to read characters
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from the input stream, and to push them back into the input stream respectively.
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The third argument is a pointer to a null terminate string which is the first
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word after #pragma. The expression supplied by HANDLE_PRAGMA should return
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nonzero if it parsed and implemented the pragma. Otherwise it should return
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zero, and leave the input stream as it was before the expression was evaluated.
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A new back-end definable macro has been added: INSERT_ATTRIBUTES. This macro
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allows backend to add attributes to decls as they are created.
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Jun 10, 1998:
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The interface to lang_decode_option has changed. It now uses and argc/argv
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interface to allow for options that use more than one input string. The new
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declaration is: int lang_decode_option (int argc, char** argv). It now
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returns the number of input strings processed, or 0 if the option is
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unknown.
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Jun 7, 1998:
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Front-ends must now define lang_init_options. It is safe for this
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function to do nothing. See c-lang.c.
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Apr 21, 1998:
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Front ends which link with c-common or other files from the C/C++
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front-ends may need to handle TI types. Look for references to
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[unsigned]int_DI_type_node in your front end. If you have references
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to these variables, you'll need up update the front end.
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To update the front end you must mirror all the code which currently
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deals with intDI_type_node to also handle intTI_type_node.
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Apr 7, 1998:
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The interface between toplev.c and the language front ends for opening the
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source file has changed:
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o init_lex() has been renamed to init_parse (char *filename) where filename
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is the name of the source file.
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o The code in toplev.c which opened the source file should be moved to
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the new init_parse function.
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o toplev.c now calls finish_parse() instead of closing the source file
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using fclose(). This should now be done in finish_parse, if necessary.
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Apr 1, 1998:
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Front-ends must now define lang_print_xnode. It is safe for this
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function to do nothing. See c-lang.c.
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Feb 1, 1998:
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GCC used to store structure sizes & offsets to elements as bitsize
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quantities. This causes problems because a structure can only be
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(target memsize / 8) bytes long (this may effect arrays too). This
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is particularly problematical on machines with small address spaces.
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So:
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All trees that represent sizes in bits should have a TREE_TYPE of
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bitsizetype (rather than sizetype).
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Accordingly, when such values are computed / initialized, care has to
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be takes to use / compute the proper type.
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When a size in bits is converted into a size in bytes, which is expressed
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in trees, care should be taken to change the tree's type again to sizetype.
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We've updated C, C++, Fortran & Objective-C to work with the new
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scheme. Other languages will need to be updated accordingly.
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Contact amylaar@cygnus.com for additional information.
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?? 1997:
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In an effort to decrease cache thrashing and useless loads we've changed the
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third argument to the DEFTREECODE macro to be a single char. This will
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affect languages that defined their own tree codes (usually in a .def file).
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Old way:
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DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", "d", 0)
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New way:
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DEFTREECODE (CLASS_METHOD_DECL, "class_method_decl", 'd', 0)
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