[PATCH][RFC] Pointer to integer conversion

[Richard Guenther <rguenther at suse dot de>]

After some discussion about the implementation defined conversion
of a pointer to a larger integer I was pointed to 
convert.c:convert_to_integer which does

  switch (TREE_CODE (intype))
    {
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      if (integer_zerop (expr))
        return build_int_cst (type, 0);

      /* Convert to an unsigned integer of the correct width first,
         and from there widen/truncate to the required type.  */
      expr = fold_build1 (CONVERT_EXPR,
                          lang_hooks.types.type_for_size (POINTER_SIZE, 
0),
                          expr);
      return fold_build1 (NOP_EXPR, type, expr);


note, that the comment doesn't match the code, as we are requesting
a signed integer from type_for_size (which in turn matches the
implement-c.texi documentation which says our pointers are signed).

I really question if the middle-end is supposed to make any such
decision here - either the frontend or the backend should decide
if pointers are signed or unsigned.  So what about the patch below?
check-gcc tested.

Richard.


Index: convert.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/convert.c,v
retrieving revision 1.70
diff -c -3 -p -r1.70 convert.c
*** convert.c	5 Oct 2005 17:29:41 -0000	1.70
--- convert.c	10 Oct 2005 19:32:02 -0000
*************** convert_to_integer (tree type, tree expr
*** 386,392 ****
!        /* Convert to an unsigned integer of the correct width first,
  	 and from there widen/truncate to the required type.  */
        expr = fold_build1 (CONVERT_EXPR,
! 			  lang_hooks.types.type_for_size (POINTER_SIZE, 0),
  			  expr);
        return fold_build1 (NOP_EXPR, type, expr);
  
--- 386,393 ----
!        /* Convert to an integer of the correct width and signedness first,
  	 and from there widen/truncate to the required type.  */
        expr = fold_build1 (CONVERT_EXPR,
! 			  lang_hooks.types.type_for_size (POINTER_SIZE,
! 							  TYPE_UNSIGNED (intype)),
  			  expr);
        return fold_build1 (NOP_EXPR, type, expr);