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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107043] range information not used in popcount
Date: Tue, 27 Sep 2022 15:22:20 +0000	[thread overview]
Message-ID: <bug-107043-4-ZlD9GxLB1V@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-107043-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107043

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I think ccp tracks instead a pair of value and mask,
X & ~mask == value & ~mask.
So, set bits in the mask mean don't know if the bit is set or clear,
clear bits mean we know it and the corresponding bit in value says if it is
known to be zero or non-zero.
That way we can express these 5 bits are known to be zero and these other 3
bits are known to be set, the rest unknown.

  parent reply	other threads:[~2022-09-27 15:22 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-26 20:10 [Bug tree-optimization/107043] New: " drepper.fsp+rhbz at gmail dot com
2022-09-26 20:27 ` [Bug tree-optimization/107043] " pinskia at gcc dot gnu.org
2022-09-27 10:19 ` drepper.fsp+rhbz at gmail dot com
2022-09-27 14:29 ` aldyh at gcc dot gnu.org
2022-09-27 15:22 ` jakub at gcc dot gnu.org [this message]
2023-07-12 21:16 ` cvs-commit at gcc dot gnu.org
2023-07-12 21:19 ` aldyh at gcc dot gnu.org

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