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From: "navidrahimi at microsoft dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/98956] Failure to optimize out boolean left
 shift
Date: Wed, 17 Nov 2021 04:59:41 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98956

Navid Rahimi <navidrahimi at microsoft dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |navidrahimi at microsoft d=
ot com

--- Comment #3 from Navid Rahimi <navidrahimi at microsoft dot com> ---
I am sending a patch for this:

/* cmp : =3D=3D, !=3D */
/* ((B0 << CST) cmp 0) -> B0 cmp 0 */
(for cmp (eq ne)
 (simplify
  (cmp (lshift (convert @0) INTEGER_CST@1) integer_zerop@2)
  (if (TREE_CODE (TREE_TYPE (@0)) =3D=3D BOOLEAN_TYPE) (cmp @0 @2))))


This does not apply to other arithmetic operations (at least it is not
verifiable). and for cases that it does apply to other arithmetic operators,
GCC already produces optimized code. You can play with the codegen I link
below:

Codegen:
https://compiler-explorer.com/z/nj4PTrecW

Proof:
https://alive2.llvm.org/ce/z/jyJAoS=