Re: Q about Ada and value ranges in types

[kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)]

Sorry it took me so long to get to this.

    > You're not showing where this comes from, so it's hard to say.  However
    > D.1480 is created by the gimplifier, not the Ada front end.  There could
    > easily be a typing problem in the tree there (e.g., that of the
    > subtraction) but I can't tell for sure.

As it turned out, there was.

    So, after calling sinfo__chars() and subtracting 300000361, the
    FE is emitting that range check.  AFAICT, the call to
    sinfo__chars(e_5) comes from ada/sem_intr.adb:148

	     Nam : constant Name_Id   := Chars (E);

    and 'if (D.1480_32 <= 1)' is at line 155:

I'd also assumed this was where the bogus tree came from, but I was wrong.
The node in question was not made by the Ada front end but by
build_range_check in clearly incorrect code that does the subtraction in the
wrong type.

This fixes that problem.  Are you in a position to check if it fixes the
original issue?

*** fold-const.c	25 Jun 2005 01:59:57 -0000	1.599
--- fold-const.c	27 Jun 2005 20:44:56 -0000
*************** build_range_check (tree type, tree exp, 
*** 4027,4034 ****
  
    if (value != 0 && ! TREE_OVERFLOW (value))
!     return build_range_check (type,
! 			      fold_build2 (MINUS_EXPR, etype, exp, low),
! 			      1, fold_convert (etype, integer_zero_node),
! 			      value);
  
    return 0;
--- 4027,4045 ----
  
    if (value != 0 && ! TREE_OVERFLOW (value))
!     {
!       /* There is no requirement that LOW be within the range of ETYPE
! 	 if the latter is a subtype.  It must, however, be within the base
! 	 type of ETYPE.  So be sure we do the subtraction in that type.  */
!       if (TREE_TYPE (etype))
! 	{
! 	  etype = TREE_TYPE (etype);
! 	  value = fold_convert (etype, value);
! 	}
! 
!       return build_range_check (type,
! 				fold_build2 (MINUS_EXPR, etype, exp, low),
! 				1, fold_convert (etype, integer_zero_node),
! 				value);
!     }
  
    return 0;