From: Helmut Eller <eller.helmut@gmail.com>
To: "Mattias Engdegård" <mattias.engdegard@gmail.com>
Cc: Eli Zaretskii <eliz@gnu.org>,
gerd.moellmann@gmail.com, emacs-devel@gnu.org
Subject: Re: MPS prstack
Date: Mon, 27 May 2024 16:54:52 +0200 [thread overview]
Message-ID: <87ikyzl2yr.fsf@gmail.com> (raw)
In-Reply-To: <8E2D3922-AD21-4638-BFAA-FC4DF49284D6@gmail.com> ("Mattias Engdegård"'s message of "Mon, 27 May 2024 16:37:56 +0200")
On Mon, May 27 2024, Mattias Engdegård wrote:
> 27 maj 2024 kl. 16.15 skrev Helmut Eller <eller.helmut@gmail.com>:
>
>> prstack.stack[prstack.sp] = e;
>> __atomic_store_n (&prstack.sp, prstack.sp + 1, __ATOMIC_SEQ_CST);
>
> Surely that is a severe overkill when all we need is a compiler barrier?
> Or have I misunderstood the context the scanners are called in?
> Shouldn't they have the same view of memory as the mutator?
The __atomic_store_n mainly prevents the compiler from reordering
instructions. The generated code uses xchg in one version and mov in
the other. I doubt that it makes any difference to the hardware, but
using __atomic_store_n documents a subtle point.
next prev parent reply other threads:[~2024-05-27 14:54 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-20 17:54 MPS prstack Helmut Eller
2024-05-20 18:21 ` Gerd Möllmann
2024-05-20 18:32 ` Helmut Eller
2024-05-21 3:30 ` Gerd Möllmann
2024-05-22 16:27 ` Helmut Eller
2024-05-22 17:55 ` Gerd Möllmann
2024-05-24 14:17 ` Helmut Eller
2024-05-24 14:27 ` Gerd Möllmann
2024-05-25 13:45 ` Gerd Möllmann
2024-05-27 7:27 ` Helmut Eller
2024-05-27 8:43 ` Gerd Möllmann
2024-05-27 9:15 ` Helmut Eller
2024-05-27 9:47 ` Gerd Möllmann
2024-05-27 11:45 ` Eli Zaretskii
2024-05-27 12:39 ` Helmut Eller
2024-05-27 13:12 ` Eli Zaretskii
2024-05-27 14:15 ` Helmut Eller
2024-05-27 14:37 ` Mattias Engdegård
2024-05-27 14:54 ` Helmut Eller [this message]
2024-05-27 14:43 ` Po Lu
2024-05-27 15:08 ` Helmut Eller
2024-05-27 11:34 ` Eli Zaretskii
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