import from github

agbcc/gcc_arm/LANGUAGES

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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 incompatable
+changes we've made.
+
+Aug 31, 1998:
+  The interface to HANDLE_PRAGMA has changed.  It now takes three arguments.
+  The first two are pointers to functions that should be used to read characters
+  from the input stream, and to push them back into the input stream respectively.
+  The third argument is a pointer to a null terminate string which is the first
+  word after #pragma.  The expression supplied by HANDLE_PRAGMA should return
+  non-zero if it parsed and implemented the pragma.  Otherwise it should return
+  zero, and leave the input stream as it was before the expression was evaluated.
+
+  A new back-end definable macro has been added: INSERT_ATTRIBUTES.  This macro
+  allows backend to add attributes to decls as they are created.
+
+Jun 10, 1998:
+  The interface to lang_decode_option has changed. It now uses and argc/argv
+  interface to allow for options that use more than one input string. The new
+  declaration is: int lang_decode_option (int argc, char** argv). It now
+  returns the number of input strings processed, or 0 if the option is
+  unknown.
+
+Jun  7, 1998:
+  Front-ends must now define lang_init_options.  It is safe for this
+  function to do nothing.  See c-lang.c.
+
+Apr 21, 1998:
+  Front ends which link with c-common or other files from the C/C++
+  front-ends may need to handle TI types.  Look for references to
+  [unsigned]int_DI_type_node in your front end.  If you have references
+  to these variables, you'll need up update the front end.
+
+  To update the front end you must mirror all the code which currently
+  deals with intDI_type_node to also handle intTI_type_node.
+
+
+Apr 7, 1998:
+  The interface between toplev.c and the language front ends for opening the
+  source file has changed:
+
+  o init_lex() has been renamed to init_parse (char *filename) where filename
+    is the name of the source file.
+  o The code in toplev.c which opened the source file should be moved to
+    the new init_parse function.
+  o toplev.c now calls finish_parse() instead of closing the source file
+    using fclose(). This should now be done in finish_parse, if necessary.
+
+Apr 1, 1998:
+  Front-ends must now define lang_print_xnode.  It is safe for this
+  function to do nothing.  See c-lang.c.
+
+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.
+
+    We've updated C, C++, Fortran & Objective-C to work with the new
+    scheme.  Other languages will need to be updated accordingly.
+    Contact amylaar@cygnus.com for additional information.
+
+?? 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
+  effect 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)