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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/94899] Failure to optimize out add before
 compare with INT_MIN
Date: Fri, 01 May 2020 01:37:16 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94899

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
/* X + Z < Y + Z is the same as X < Y when there is no overflow.  */
(for op (lt le ge gt)
 (simplify
  (op (plus:c @0 @2) (plus:c @1 @2))
  (if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
       && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
   (op @0 @1))))
...
/* X - Z < Y - Z is the same as X < Y when there is no overflow.  */
(for op (lt le ge gt)
 (simplify
  (op (minus @0 @2) (minus @1 @2))
  (if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
       && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
   (op @0 @1))))

This is invalid as 0x80000000 is unsigned (C90/C++03) or long (C99/C++11) in
type.
Which means then overflow is not undefined but rather wrapping.

THIS ALSO means clang is broken.=