From: Richard Biener <rguenther@suse.de>
To: Jason Merrill <jason@redhat.com>
Cc: Nathaniel Shead <nathanieloshead@gmail.com>, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] c++: End lifetime of objects in constexpr after destructor call [PR71093]
Date: Sun, 10 Dec 2023 11:22:28 +0100 [thread overview]
Message-ID: <F55D5934-35C0-4641-A7FB-D0EA8F647813@suse.de> (raw)
In-Reply-To: <a7ca6f02-e73a-4f2c-b6f5-fe4d8dc10bfe@redhat.com>
> Am 09.12.2023 um 21:13 schrieb Jason Merrill <jason@redhat.com>:
>
> On 11/2/23 21:18, Nathaniel Shead wrote:
>> Bootstrapped and regtested on x86-64_pc_linux_gnu.
>> I'm not entirely sure if the change I made to have destructors clobber with
>> CLOBBER_EOL instead of CLOBBER_UNDEF is appropriate, but nothing seemed to have
>> broken by doing this and I wasn't able to find anything else that really
>> depended on this distinction other than a warning pass. Otherwise I could
>> experiment with a new clobber kind for destructor calls.
>
> It seems wrong to me: CLOBBER_EOL is documented to mean that the storage is expiring at that point as well, which a (pseudo-)destructor does not imply; it's perfectly valid to destroy an object and then create another in the same storage.
>
> We probably do want another clobber kind for end of object lifetime. And/or one for beginning of object lifetime.
There’s not much semantically different between UNDEF and end of object but not storage lifetime? At least for what middle-end optimizations do.
EOL is used by stack slot sharing and that operates on the underlying storage, not individual objects live in it.
Richard
> Jason
>
next prev parent reply other threads:[~2023-12-10 10:22 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-03 1:18 Nathaniel Shead
2023-11-03 1:34 ` Nathaniel Shead
2023-11-27 11:08 ` Nathaniel Shead
2023-12-09 20:12 ` Jason Merrill
2023-12-10 10:22 ` Richard Biener [this message]
2023-12-10 11:21 ` Alexander Monakov
2023-12-10 15:58 ` Richard Biener
2023-12-10 18:34 ` Jason Merrill
2023-12-11 8:02 ` Richard Biener
2023-12-11 19:12 ` Jason Merrill
2023-12-11 19:17 ` Richard Biener
2023-12-11 19:21 ` Marek Polacek
2023-12-11 22:00 ` Jason Merrill
2023-12-11 22:22 ` Marek Polacek
2023-12-11 23:03 ` Jakub Jelinek
2023-12-12 11:13 ` Alexander Monakov
2023-12-12 11:15 ` Jakub Jelinek
2023-12-12 15:24 ` Jason Merrill
2023-12-12 17:50 ` Jason Merrill
2023-12-13 4:40 ` Jason Merrill
2023-12-13 16:47 ` [pushed 1/4] c++: copy location to AGGR_INIT_EXPR Jason Merrill
2023-12-13 16:47 ` [pushed 2/4] c++: constant direct-initialization [PR108243] Jason Merrill
2023-12-13 16:47 ` [pushed 3/4] c++: fix in-charge parm in constexpr Jason Merrill
2023-12-13 16:47 ` [pushed 4/4] c++: End lifetime of objects in constexpr after destructor call [PR71093] Jason Merrill
2023-12-13 18:05 ` [pushed 1/4] c++: copy location to AGGR_INIT_EXPR Patrick Palka
2023-12-13 20:06 ` [pushed] c++: TARGET_EXPR location in default arg [PR96997] Jason Merrill
2023-12-14 0:00 ` [pushed 1/4] c++: copy location to AGGR_INIT_EXPR Marek Polacek
2023-12-14 1:38 ` Jason Merrill
2023-12-14 14:25 ` Marek Polacek
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