From: Jakub Jelinek <jakub@redhat.com>
To: Tobias Burnus <tobias@codesourcery.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>, fortran <fortran@gcc.gnu.org>
Subject: Re: [Patch] OpenMP: Support acquires/release in 'omp require atomic_default_mem_order'
Date: Fri, 8 Dec 2023 14:47:41 +0100 [thread overview]
Message-ID: <ZXMefWsqrdTsl384@tucnak> (raw)
In-Reply-To: <e15951ed-3430-46bf-9a5f-2d57c16452d0@codesourcery.com>
On Tue, Nov 28, 2023 at 12:28:05PM +0100, Tobias Burnus wrote:
> I stumbled over this omission when looking at Sandra's patch. It turned out that this is
> a new OpenMP 5.2 feature - probably added to simplify/unify the syntax. I guess the reason
> that release/acquire wasn't added before is that it cannot be universally be used - read/write
> do only accept one of them.
I thought when this was discussed that it was meant to behave right (choose
some more appropriate memory model if one was not allowed), but reading 5.2
I think that is not what ended up in the spec, because [213:11-13] says that
atomic_default_mem_order is as if the argument appeared on any atomic
directive without explicit mem-order clause and atomic directive has the
[314:9-10] restrictions.
I'd bring this to omp-lang whether it was really meant that
#pragma omp requires atomic_default_mem_order (release)
int foo (int *p) {
int t;
#pragma omp atomic read
t = *p;
return t;
}
and
#pragma omp requires atomic_default_mem_order (acquire)
void bar (int *p) {
#pragma omp atomic write
*p = 0;
}
are meant to be invalid.
Another comment, atomic_default_mem_order arguments aren't handled
just in the requires parsing, but also in context selectors.
So, the additions would need to be reflected in
omp_check_context_selector and omp_context_selector_matches
as well.
Jakub
prev parent reply other threads:[~2023-12-08 13:47 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-28 11:28 Tobias Burnus
2023-12-08 13:47 ` Jakub Jelinek [this message]
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