Re: [PATCH] Fix up foperator_abs::op1_range [PR107569]

[Aldy Hernandez <aldyh@redhat.com>]

On Wed, Nov 9, 2022 at 11:55 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> foperator_abs::op1_range works except for the NaN handling,
> from:
> [frange] double [-Inf, 1.79769313486231570814527423731704356798070567525844996599e+308 (0x0.fffffffffffff8p+1024)]
> lhs it computes r
> [frange] double [-1.79769313486231570814527423731704356798070567525844996599e+308 (-0x0.fffffffffffff8p+1024), 1.79769313486231570814527423731704356798070567525844996599e+308 (0x0.fffffffffffff8p+1024)] +-NAN
> which is correct except for the +-NAN part.
> For r before the final step it makes sure to add -NAN if there is +NAN
> in the lhs range, but the final r.union_ makes it unconditional +-NAN,
> because the frange ctor sets +-NAN.
> So, I think we need to clear it (or have some set variant which
> says not to set NAN).
>
> This patch fixes that, but isn't enough to fix the PR, something in
> the assumptions handling is still broken (and the PR has other parts).

LGTM.

Sorry I haven't gotten to the PR yet.  I'll poke at it later today.

Thanks.
Aldy

>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2022-11-09  Jakub Jelinek  <jakub@redhat.com>
>
>         PR tree-optimization/107569
>         * range-op-float.cc (foperator_abs::op1_range): Clear NaNs
>         from the negatives frange before unioning it into r.
>
> --- gcc/range-op-float.cc.jj    2022-11-06 11:56:27.138137781 +0100
> +++ gcc/range-op-float.cc       2022-11-08 18:13:18.026974667 +0100
> @@ -1280,9 +1280,10 @@ foperator_abs::op1_range (frange &r, tre
>      return true;
>    // Then add the negative of each pair:
>    // ABS(op1) = [5,20] would yield op1 => [-20,-5][5,20].
> -  r.union_ (frange (type,
> -                   real_value_negate (&positives.upper_bound ()),
> -                   real_value_negate (&positives.lower_bound ())));
> +  frange negatives (type, real_value_negate (&positives.upper_bound ()),
> +                   real_value_negate (&positives.lower_bound ()));
> +  negatives.clear_nan ();
> +  r.union_ (negatives);
>    return true;
>  }
>
>
>         Jakub
>