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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/95408] Failure to optimize bitwise and with
 negated conditional using the same operand to conditional with decremented
 operand
Date: Sat, 13 May 2023 05:47:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95408

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot =
gnu.org
   Last reconfirmed|                            |2023-05-13
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
For unsigned x (to simplify things first).
In forwardprop4 we have
  _1 =3D x_4(D) <=3D 121211;
  _3 =3D _1 ? x_4(D) : 0;
  _5 =3D _3 !=3D 0;

This could be done as:
x_4(D) <=3D 121211 ? x_4(D) !=3D 0 : 0

Which then would be:
(x_4(D) <=3D 121211 & x_4(D) !=3D 0)=20
((x_4(D) - 1) <=3D 121210)

So I have a patch which does the second step into the 3rd expression (there=
 is
another bug or 2 about it). the 3rd expression into the final is already do=
ne.
It is just the first that needs to happen to written up.

Something like this for the first step.
(for op (tcc_comparison)
/* (c ? a : CST0) op CST1  -->  c ? (a op CST1) : (CST0 op CST1) */
 (simplify
  (op (cond:s @0 @1 CONSTANT_CLASS_P@2) CONSTANT_CLASS_P@3)
  (cond! @0 (op @1 @3) (op @2 @4)))

So mine.=