Re: Q about Ada and value ranges in types

[ja2morri@csclub.uwaterloo.ca (James A. Morrison)]

kenner@vlsi1.ultra.nyu.edu (Richard Kenner) writes:

> 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),
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 RTH has been suggesting to use build_int_cst (etype, 0) instead.

> ! 				value);
> !     }
>   
>     return 0;
> 


-- 
Thanks,
Jim

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