The GNU Modula-2 front end to GCC

The PIM system module

DEFINITION MODULE SYSTEM ;

(*
   Description: Implements the SYSTEM dependent module
                in the Modula-2 compiler.
*)

EXPORT QUALIFIED BITSPERBYTE, BYTESPERWORD,
                 LOC, WORD, BYTE, ADDRESS, INTEGER8,
                 INTEGER16, INTEGER32, INTEGER64, CARDINAL8,
                 CARDINAL16, CARDINAL32, CARDINAL64, WORD16,
                 WORD32, WORD64, BITSET8, BITSET16,
                 BITSET32, REAL32, REAL64, REAL96,
                 REAL128, COMPLEX32, COMPLEX64, COMPLEX96,
                 COMPLEX128,
                 ADR, TSIZE, ROTATE, SHIFT, THROW, TBITSIZE ;
                 (* SIZE is also exported if -fpim2 is used *)

CONST

  BITSPERBYTE   = __ATTRIBUTE__ __BUILTIN__ ((BITS_PER_UNIT)) ;

  BYTESPERWORD  = __ATTRIBUTE__ __BUILTIN__ ((UNITS_PER_WORD)) ;


(* all the following types are declared internally to gm2
TYPE

   LOC ;

   WORD ;

   BYTE ;

   ADDRESS ;

   INTEGER8 ;

   INTEGER16 ;

   INTEGER32 ;

   INTEGER64 ;

   CARDINAL8 ;

   CARDINAL16 ;

   CARDINAL32 ;

   CARDINAL64 ;

   WORD16 ;

   WORD32 ;

   WORD64 ;

   BITSET8 ;

   BITSET16 ;

   BITSET32 ;

   REAL32 ;

   REAL64 ;

   REAL96 ;

   REAL128 ;

   COMPLEX32 ;

   COMPLEX64 ;

   COMPLEX96 ;

   COMPLEX128 ;
*)


(*
   all the functions below are declared internally to gm2
   ====================================================


PROCEDURE ADR (VAR v: <anytype>): ADDRESS;
  (* Returns the address of variable v. *)


PROCEDURE SIZE (v: <type>) : ZType;
  (* Returns the number of BYTES used to store a v of
     any specified <type>.  Only available if -fpim2 is used.
  *)


PROCEDURE TSIZE (<type>) : CARDINAL;
  (* Returns the number of BYTES used to store a value of the
     specified <type>.
  *)


PROCEDURE ROTATE (val: <a set type>;
                  num: INTEGER): <type of first parameter>;
  (* Returns a bit sequence obtained from val by rotating up or down
     (left or right) by the absolute value of num.  The direction is
     down if the sign of num is negative, otherwise the direction is up.
  *)


PROCEDURE SHIFT (val: <a set type>;
                 num: INTEGER): <type of first parameter>;
  (* Returns a bit sequence obtained from val by shifting up or down
     (left or right) by the absolute value of num, introducing
     zeros as necessary.  The direction is down if the sign of
     num is negative, otherwise the direction is up.
  *)


PROCEDURE THROW (i: INTEGER) ;
  (*
     THROW is a GNU extension and was not part of the PIM or ISO
     standards.  It throws an exception which will be caught by the EXCEPT
     block (assuming it exists).  This is a compiler builtin function which
     interfaces to the GCC exception handling runtime system.
     GCC uses the term throw, hence the naming distinction between
     the GCC builtin and the Modula-2 runtime library procedure Raise.
     The later library procedure Raise will call SYSTEM.THROW after
     performing various housekeeping activities.
  *)


PROCEDURE TBITSIZE (<type>) : CARDINAL ;
  (* Returns the minimum number of bits necessary to represent
     <type>.  This procedure function is only useful for determining
     the number of bits used for any type field within a packed RECORD.
     It is not particularly useful elsewhere since <type> might be
     optimized for speed, for example a BOOLEAN could occupy a WORD.
  *)
*)

(* The following procedures are invoked by GNU Modula-2 to
   shift non word sized set types. They are not strictly part
   of the core PIM Modula-2, however they are used by
   GNU Modula-2 to implement the SHIFT procedure defined above,
   which are in turn used by the Logitech compatible libraries.

   Users will access these procedures by using the procedure
   SHIFT above and GNU Modula-2 will map SHIFT onto one of
   the following procedures.
*)

(*
   ShiftVal - is a runtime procedure whose job is to implement
              the SHIFT procedure of ISO SYSTEM. GNU Modula-2 will
              inline a SHIFT of a single WORD sized set and will only
              call this routine for larger sets.
*)


PROCEDURE ShiftVal (VAR s, d: ARRAY OF BITSET;
                    SetSizeInBits: CARDINAL;
                    ShiftCount: INTEGER) ;


(*
   ShiftLeft - performs the shift left for a multi word set.
               This procedure might be called by the back end of
               GNU Modula-2 depending whether amount is known at compile
               time.
*)


PROCEDURE ShiftLeft (VAR s, d: ARRAY OF BITSET;
                     SetSizeInBits: CARDINAL;
                     ShiftCount: CARDINAL) ;

(*
   ShiftRight - performs the shift left for a multi word set.
                This procedure might be called by the back end of
                GNU Modula-2 depending whether amount is known at compile
                time.
*)


PROCEDURE ShiftRight (VAR s, d: ARRAY OF BITSET;
                     SetSizeInBits: CARDINAL;
                     ShiftCount: CARDINAL) ;


(*
   RotateVal - is a runtime procedure whose job is to implement
               the ROTATE procedure of ISO SYSTEM. GNU Modula-2 will
               inline a ROTATE of a single WORD (or less)
               sized set and will only call this routine for larger sets.
*)


PROCEDURE RotateVal (VAR s, d: ARRAY OF BITSET;
                     SetSizeInBits: CARDINAL;
                     RotateCount: INTEGER) ;


(*
   RotateLeft - performs the rotate left for a multi word set.
                This procedure might be called by the back end of
                GNU Modula-2 depending whether amount is known at compile
                time.
*)


PROCEDURE RotateLeft (VAR s, d: ARRAY OF BITSET;
                      SetSizeInBits: CARDINAL;
                      RotateCount: CARDINAL) ;


(*
   RotateRight - performs the rotate right for a multi word set.
                 This procedure might be called by the back end of
                 GNU Modula-2 depending whether amount is known at compile
                 time.
*)


PROCEDURE RotateRight (VAR s, d: ARRAY OF BITSET;
                       SetSizeInBits: CARDINAL;
                       RotateCount: CARDINAL) ;


END SYSTEM.

The different dialects of Modula-2 PIM-[234] and ISO Modula-2 declare the function SIZE in different places. PIM-[34] and ISO Modula-2 declare SIZE as a pervasive function (declared in the base module). PIM-2 defined SIZE in the SYSTEM module (as shown above).

GNU Modula-2 allows users to specify the dialect of Modula-2 by using the -fiso and -fpim2 command line switches.