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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/109441] missed optimization when all elements
 of vector are known
Date: Tue, 11 Apr 2023 13:17:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109441

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-04-11
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
            Version|unknown                     |13.0
                 CC|                            |rguenth at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Well, it doesn't need std::vector for this, a C testcase with a large enough
array (> 16 elements, the unroll limit) suffers from the same "problem".

But IMHO it's academic, right?

GCC only transforms loopy code like you suggest by complete peeling of the
loop, it doesn't attempt to "simulate" IL (and if, then it would only up
to some complexity limit).=