gcc/LANGUAGES

   1 Right now there is no documentation for the GCC tree -> rtl interfaces
   2 (or more generally the interfaces for adding new languages).
   3
   4 Such documentation would be of great benefit to the project.  Until such
   5 time as we can formally start documenting the interface this file will
   6 serve as a repository for information on these interface and any incompatable
   7 changes we've made.
   8
   9
  10 Feb 1, 1998:
  11
  12   GCC used to store structure sizes & offsets to elements as bitsize
  13   quantities.  This causes problems because a structure can only be
  14   (target memsize / 8) bytes long (this may effect arrays too).  This
  15   is particularly problematical on machines with small address spaces.
  16
  17   So:
  18
  19     All trees that represent sizes in bits should have a TREE_TYPE of
  20     bitsizetype (rather than sizetype).
  21
  22     Accordingly, when such values are computed / initialized, care has to
  23     be takes to use / compute the proper type.
  24
  25     When a size in bits is converted into a size in bytes, which is expressed
  26     in trees, care should be taken to change the tree's type again to sizetype.
  27
  28     We've updated C, C++, Fortran & Objective-C to work with the new
  29     scheme.  Other languages will need to be updated accordingly.
  30     Contact amylaar@cygnus.com for additional information.
  31
  32