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From: "thiago at kde dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/109896] Missed optimisation: overflow detection in multiplication instructions for operator new
Date: Thu, 18 May 2023 00:13:07 +0000	[thread overview]
Message-ID: <bug-109896-4-K51TmmAxhT@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-109896-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109896

--- Comment #5 from Thiago Macieira <thiago at kde dot org> ---
(In reply to Andrew Pinski from comment #4)
> If you are that picky for cycles, these cycles are not going to be a problem
> compared to the dynamic allocation that is just about to happen ......

Yeah, I realised that after I posted the reply. If the calculation is
successful, we're going to allocate memory and that's neither fast nor
determinstic. If it overflows, we're going to unwind the stack, which is even
worse. I had only looked at the multiplication and failed to consider what
comes after it.

So, yeah, do this if it's a low-hanging fruit.

  parent reply	other threads:[~2023-05-18  0:13 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-17 18:34 [Bug target/109896] New: " thiago at kde dot org
2023-05-17 18:45 ` [Bug target/109896] " pinskia at gcc dot gnu.org
2023-05-17 20:39 ` hjl.tools at gmail dot com
2023-05-17 23:42 ` thiago at kde dot org
2023-05-17 23:46 ` pinskia at gcc dot gnu.org
2023-05-18  0:13 ` thiago at kde dot org [this message]
2023-05-18  8:33 ` redi at gcc dot gnu.org
2023-05-18 14:08 ` thiago at kde dot org
2024-06-06 16:49 ` [Bug c++/109896] " pinskia at gcc dot gnu.org
2024-06-06 22:03 ` pinskia at gcc dot gnu.org
2024-06-07  1:42 ` pinskia at gcc dot gnu.org
2024-06-07 14:05 ` pinskia at gcc dot gnu.org

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