ABS_EXPR anti range handling in extract_range_from_unary_expr() useless?

[Aldy Hernandez]

Howdy.

I'm looking at the ABS_EXPR code in extract_range_from_unary_expr() and 
have noticed that by the time we get here:

       /* If a VR_ANTI_RANGEs contains zero, then we have
	 ~[-INF, min(MIN, MAX)].  */
       if (vr0.type == VR_ANTI_RANGE)

...we have already handled VR_VARYING, VR_UNDEFINED, and symbolics. 
Which means, we only have VR_RANGE of constants to deal with. 
Furthermore, we have previously split a VR_ANTI_RANGE into its 
constituents and handled them piecemeal:

   /* Now canonicalize anti-ranges to ranges when they are not symbolic
      and express op ~[]  as (op []') U (op []'').  */
   if (vr0.type == VR_ANTI_RANGE
       && ranges_from_anti_range (&vr0, &vrtem0, &vrtem1))

Am I missing something, or is this entire block dead code?

>       /* If a VR_ANTI_RANGEs contains zero, then we have
> 	 ~[-INF, min(MIN, MAX)].  */
>       if (vr0.type == VR_ANTI_RANGE)
> 	{
> 	  if (range_includes_zero_p (vr0.min, vr0.max) == 1)
> 	    {
> 	      /* Take the lower of the two values.  */
> 	      if (cmp != 1)
> 		max = min;
> 
> 	      /* Create ~[-INF, min (abs(MIN), abs(MAX))]
> 	         or ~[-INF + 1, min (abs(MIN), abs(MAX))] when
> 		 flag_wrapv is set and the original anti-range doesn't include
> 	         TYPE_MIN_VALUE, remember -TYPE_MIN_VALUE = TYPE_MIN_VALUE.  */
> 	      if (TYPE_OVERFLOW_WRAPS (type))
> 		{
> 		  tree type_min_value = TYPE_MIN_VALUE (type);
> 
> 		  min = (vr0.min != type_min_value
> 			 ? int_const_binop (PLUS_EXPR, type_min_value,
> 					    build_int_cst (TREE_TYPE (type_min_value), 1))
> 			 : type_min_value);
> 		}
> 	      else
> 		min = TYPE_MIN_VALUE (type);
> 	    }
> 	  else
> 	    {
> 	      /* All else has failed, so create the range [0, INF], even for
> 	         flag_wrapv since TYPE_MIN_VALUE is in the original
> 	         anti-range.  */
> 	      vr0.type = VR_RANGE;
> 	      min = build_int_cst (type, 0);
> 	      max = TYPE_MAX_VALUE (type);
> 	    }
> 	}

I tried putting a gcc_unreachable() there, and it never gets triggered 
in either a bootstrap or a full test run.  I also tried exercising 
programmatically extract_range_from_unary_expr() for the entire domain 
of a signed char and unsigned char, with and without flag_wrapv (ranges 
and anti-ranges), and I can't get the above code to trigger.

Thanks.
Aldy