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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109008] [13 Regression] Wrong code in scipy
 package since r13-3926-gd4c2f1d376da6f
Date: Fri, 03 Mar 2023 13:14:03 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109008

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #8)
> We basically have to consider an input range [a, b] as [a - x, b + y]
> with the largest positive x and y so that correctly rounding the value
> yields a and b again.

So when we have

 [a, b] =3D x + [c, d];

we have to compute

 x =3D [a + a', b + b'] - [c + c', d + d'];

and because we deal with FP actually do

 x =3D [a, b] - [c, d];
 x' =3D [a', b'] - [c', d'];

and yield x U x' as result.  For other operations it might get more
complicated.=