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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/113774] wrong code with _BitInt() arithmetics at -O2
Date: Thu, 08 Feb 2024 13:54:32 +0000	[thread overview]
Message-ID: <bug-113774-4-c47EcvttLo@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-113774-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113774

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 57359
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57359&action=edit
gcc14-pr113774.patch

So far lightly tested optimization on the bitint lowering side which emits
more optimal code for that (for the unsigned 255 -> 257 bit extension and
m_upwards_2limb low is 3 and high is 4, so when processing first limb in the
loop, the idx < 3 condition is always true (as idx is 0 or 2) and when
processing the second limb in the loop, similarly idxp1 <= 3 condition is
always true (as idxp1 is 1 or 3) while idxp1 == 3 still needs to be compared.

This makes the PRE (or VN?) bug latent.

  parent reply	other threads:[~2024-02-08 13:54 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-05 18:13 [Bug tree-optimization/113774] New: " zsojka at seznam dot cz
2024-02-06 12:04 ` [Bug tree-optimization/113774] " zsojka at seznam dot cz
2024-02-07 18:28 ` jakub at gcc dot gnu.org
2024-02-07 20:24 ` jakub at gcc dot gnu.org
2024-02-08 13:54 ` jakub at gcc dot gnu.org [this message]
2024-02-08 14:04 ` rguenth at gcc dot gnu.org
2024-02-08 14:12 ` jakub at gcc dot gnu.org
2024-02-08 14:18 ` rguenth at gcc dot gnu.org
2024-02-09 10:06 ` cvs-commit at gcc dot gnu.org
2024-02-09 10:14 ` jakub at gcc dot gnu.org
2024-02-15  8:47 ` pinskia at gcc dot gnu.org

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