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From: "law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/110199] [12/13/14 Regression] Missing VRP
 transformation with MIN_EXPR and known relation
Date: Thu, 07 Mar 2024 13:34:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110199

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |law at gcc dot gnu.=
org
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-03-07
                 CC|                            |law at gcc dot gnu.org

--- Comment #6 from Jeffrey A. Law <law at gcc dot gnu.org> ---
I think this is trivial to do in DOM and not handling these cases could eas=
ily
be seen as an oversight.

When we fail to find an expression in the hash table of available expressio=
ns,
we have a bit of existing code that can ask about a relation between two
operands of a binary operator and based on that relation possibly simplify =
the
original expression.

So for example, if we have:

 _4 =3D MIN_EXPR <a_2(D), b_3(D)>;

And the MIN_EXPR expression isn't in the hash table, we look to see if we h=
ave
recorded a_2 =3D=3D b_3 and if so we simplify the MIN_EXPR into a copy.

So this is just a matter of extending that code ever so slightly to do an
additional lookup.=