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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/37516] ~(-2 - a) is not being optimized into a + 1
Date: Thu, 23 Feb 2012 08:48:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37516

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2012-02-23
         AssignedTo|unassigned at gcc dot       |pinskia at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-02-23 08:42:01 UTC ---
I have an idea on how to fix this.
basically:
~(C - X)
is the same as:
~ - (X - C)
which then can be simplified to
X - (C+1)

This should be done on both the tree level (on the pinskia/treecombine branch
in tree-ssa-fold.c) and the rtl level in simplify-rtx.c.