Re: [PATCH] [PR tree-optimization/107355] Handle NANs in abs range-op entry.

[Aldy Hernandez <aldyh@redhat.com>]

Tested on x86-64 Linux.

Pushed.

On Mon, Oct 24, 2022 at 3:33 PM Aldy Hernandez <aldyh@redhat.com> wrote:
>
> The problem here is that the threader is coming up with a path where
> the only valid result is a NAN.  When the abs op1_range entry is
> trying to add the negative posibility, it attempts to get the bounds
> of the working range.  NANs don't have bounds so they need to be
> special cased.
>
>         PR tree-optimization/107355
>
> gcc/ChangeLog:
>
>         * range-op-float.cc (foperator_abs::op1_range): Handle NAN.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/tree-ssa/pr107355.c: New test.
> ---
>  gcc/range-op-float.cc                    |  9 +++++++++
>  gcc/testsuite/gcc.dg/tree-ssa/pr107355.c | 13 +++++++++++++
>  2 files changed, 22 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr107355.c
>
> diff --git a/gcc/range-op-float.cc b/gcc/range-op-float.cc
> index 8777bc70d71..04208c88dd1 100644
> --- a/gcc/range-op-float.cc
> +++ b/gcc/range-op-float.cc
> @@ -1269,6 +1269,15 @@ foperator_abs::op1_range (frange &r, tree type,
>    positives.update_nan (/*sign=*/false);
>    positives.intersect (lhs);
>    r = positives;
> +  // Add -NAN if relevant.
> +  if (r.maybe_isnan ())
> +    {
> +      frange neg_nan;
> +      neg_nan.set_nan (type, true);
> +      r.union_ (neg_nan);
> +    }
> +  if (r.known_isnan ())
> +    return true;
>    // Then add the negative of each pair:
>    // ABS(op1) = [5,20] would yield op1 => [-20,-5][5,20].
>    r.union_ (frange (type,
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr107355.c b/gcc/testsuite/gcc.dg/tree-ssa/pr107355.c
> new file mode 100644
> index 00000000000..40796344bfb
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr107355.c
> @@ -0,0 +1,13 @@
> +// { dg-do compile }
> +// { dg-options "-O2 -fno-guess-branch-probability -fsanitize=float-cast-overflow --param=max-jump-thread-duplication-stmts=240" }
> +
> +float f;
> +
> +void
> +foo (double d)
> +{
> +  (char) f;
> +  long l = __builtin_fabs (d);
> +  (char) f;
> +  (long) d;
> +}
> --
> 2.37.3
>