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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95729] Failure to optimize away certain
 returns when the condition to reach them is a calculation that already
 results in that value
Date: Wed, 17 Nov 2021 09:41:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95729

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot =
gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
;; a !=3D b ? a - b : 0
Something like:
(simplify
 (cond (ne:c @0 @1) (minus@2 @0 @1) zero_p)
 (if (!HONOR_NANS (type) && !HONOR_SIGNED_ZEROS (type))
 @2)
(simplify
 (cond (eq:c @0 @1) zero_p (minus@2 @0 @1))
 (if (!HONOR_NANS (type) && !HONOR_SIGNED_ZEROS (type))
 @2)

Note I noticed LLVM 13 no longer does this optimization (I wonder if they h=
ave
a testsuite).=