Re: extract_range_from_binary* cleanups for VRP

[Richard Biener <richard dot guenther at gmail dot com>]

On Fri, Jun 29, 2018 at 7:55 PM Aldy Hernandez <aldyh@redhat.com> wrote:
>
> Howdy!
>
> Attached are some cleanups to the VRP code dealing with PLUS/MINUS_EXPR
> on ranges.  This will make it easier to share code with any other range
> implementation in the future, but is completely independent from any
> other work.
>
> Currently there is a lot of code duplication in the PLUS/MINUS_EXPR
> code, which we can easily abstract out and make everything easier to
> read.  I have tried to keep functionality changes to a minimum to help
> in reviewing.
>
> A few minor things that are different:
>
> 1. As mentioned in a previous thread with Richard
> (https://gcc.gnu.org/ml/gcc/2018-06/msg00100.html), I would like to use
> the first variant here, as they seem to ultimately do the same thing:
>
> -         /* Get the lower and upper bounds of the type.  */
> -         if (TYPE_OVERFLOW_WRAPS (expr_type))
> -           {
> -             type_min = wi::min_value (prec, sgn);
> -             type_max = wi::max_value (prec, sgn);
> -           }
> -         else
> -           {
> -             type_min = wi::to_wide (vrp_val_min (expr_type));
> -             type_max = wi::to_wide (vrp_val_max (expr_type));
> -           }
>
> 2. I've removed the code below, as it seems to be a remnant from when
> the comparisons were being done with double_int's.  The overflow checks
> were/are being done prior anyhow.  For that matter, I put in some
> gcc_unreachables in the code below, and never triggered it in a
> bootstrap + regtest.
>
> -         /* Check for type overflow.  */
> -         if (min_ovf == 0)
> -           {
> -             if (wi::cmp (wmin, type_min, sgn) == -1)
> -               min_ovf = -1;
> -             else if (wi::cmp (wmin, type_max, sgn) == 1)
> -               min_ovf = 1;
> -           }
> -         if (max_ovf == 0)
> -           {
> -             if (wi::cmp (wmax, type_min, sgn) == -1)
> -               max_ovf = -1;
> -             else if (wi::cmp (wmax, type_max, sgn) == 1)
> -               max_ovf = 1;
> -           }
>
> Everything else is exactly as it was, just abstracted and moved around.
>
> To test this, I compared the results of every binary op before and after
> this patch, to make sure that we were getting the same exact ranges.
> There were no differences in a bootstrap plus regtest.
>
> OK for trunk?

OK.

Thanks,
Richard.