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From: Jeff Law <jeffreyalaw@gmail.com>
To: Richard Biener <rguenther@suse.de>
Cc: gcc-patches@gcc.gnu.org, Jan Hubicka <hubicka@ucw.cz>
Subject: Re: [PATCH] Improve DSE to handle stores before __builtin_unreachable ()
Date: Thu, 22 Jun 2023 07:36:45 -0600	[thread overview]
Message-ID: <b26de798-7467-e385-abee-164296204316@gmail.com> (raw)
In-Reply-To: <nycvar.YFH.7.77.849.2306220626010.4723@jbgna.fhfr.qr>



On 6/22/23 00:31, Richard Biener wrote:
> I think there's a difference in that __builtin_trap () is observable
> while __builtin_unreachable () is not and reaching __builtin_unreachable
> () invokes undefined behavior while reaching __builtin_trap () does not.
> 
> So the isolation code marking the trapping code volatile should be
> enough and the trap () is just there to end the basic block
> (and maybe be on the safe side to really trap).
Agreed WRT observability -- but that's not really the point of the trap 
and if we wanted we could change that behavior.

The trap is there to halt execution immediately rather than letting it 
keep running.  That was a design decision from a security standpoint. 
If we've detected that we're executing undefined behavior, stop rather 
than potentially letting a malicious actor turn a bug into an exploit.

jeff

  reply	other threads:[~2023-06-22 13:36 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20230620070009.C11983858D1E@sourceware.org>
2023-06-20 13:27 ` Jeff Law
2023-06-21  6:41   ` Richard Biener
2023-06-21  9:55     ` Jan Hubicka
2023-06-21 14:04     ` Jeff Law
2023-06-22  6:31       ` Richard Biener
2023-06-22 13:36         ` Jeff Law [this message]
2023-06-22 13:42           ` Jan Hubicka
2023-06-24 14:24             ` Jeff Law
2023-06-25 16:33               ` Jan Hubicka
2023-06-26 17:21   ` Jan Hubicka
2023-06-26 22:37     ` Jeff Law
2023-06-20  6:59 Richard Biener

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