From: Jeff Law <law@redhat.com>
To: Richard Guenther <richard.guenther@gmail.com>
Cc: Aldy Hernandez <aldyh@redhat.com>,
gcc-patches <gcc-patches@gcc.gnu.org>,
Jakub Jelinek <jakub@redhat.com>
Subject: Re: [cxx-mem-model] bitfield tests
Date: Thu, 31 Mar 2011 14:58:00 -0000 [thread overview]
Message-ID: <4D949416.5000307@redhat.com> (raw)
In-Reply-To: <AANLkTi=9XUrhoX=aDKe4gpAXZTQzjbGHynRhfq-d2+=L@mail.gmail.com>
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On 03/30/11 08:19, Richard Guenther wrote:
>
> Well, I'm not sure that strict-align targets that provide byte access do
> not simply hide the issue inside the CPU (thus, perform the read-modify-write
> there and do not guarantee any atomicity unless you ask for it).
Certainly some do this internally, but that's clearly out of our
control. However, some really do sub-word accesses.
I even vaguely remember this being controllable by bits in page table
entries on one architecture. You could set the bit which meant if I ask
for a byte access, then do it byte-wise, otherwise the processor would
do a read-modify-write. Clearly this was meant to make it easier for
dealing with memory mapped devices.
Jeff
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next prev parent reply other threads:[~2011-03-31 14:48 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-29 17:28 Aldy Hernandez
2011-03-30 10:50 ` Richard Guenther
2011-03-30 14:24 ` Aldy Hernandez
2011-03-30 14:25 ` Richard Guenther
2011-03-30 14:41 ` Aldy Hernandez
2011-03-30 14:43 ` Richard Guenther
2011-03-30 15:13 ` Mike Stump
2011-03-31 14:58 ` Jeff Law [this message]
2011-03-31 15:35 ` Richard Guenther
2011-04-01 16:24 ` Richard Henderson
2011-04-01 19:42 ` Andrew Pinski
2011-04-02 7:56 ` Richard Guenther
2011-04-04 12:56 ` Aldy Hernandez
2011-04-04 12:58 ` Aldy Hernandez
2011-04-06 15:29 ` Michael Matz
2011-04-06 17:16 ` Aldy Hernandez
2011-04-04 18:06 ` Jeff Law
2011-03-30 14:39 ` Michael Matz
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