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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/94782] Simple multiplication-related
 arithmetic not optimized to direct multiplication
Date: Mon, 27 Apr 2020 07:07:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94782

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-04-27

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Since the inner (a - 1U) * b is unsigned but a * b would be signed due to
undefined signed overflow we cannot optimize to that.  But we could indeed.
optimize to (unsigned)a * (unsigned)b.  fold-const.c contains related
transforms that could be amended.  reassoc could as well but would need
enhancement for signed arithmetic.=