From: Michael Matz <matz@suse.de>
To: Richard Biener <richard.guenther@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>,
GCC Development <gcc@gcc.gnu.org>,
GNU C Library <libc-alpha@sourceware.org>,
qemu-devel@nongnu.org
Subject: Re: Disabling TLS address caching to help QEMU on GNU/Linux
Date: Thu, 22 Jul 2021 16:01:10 +0000 (UTC) [thread overview]
Message-ID: <alpine.LSU.2.20.2107221554460.10537@wotan.suse.de> (raw)
In-Reply-To: <CAFiYyc2UuO8qXhwzVQ63DhPPiBjecm7rzY2t4Z-UMiserEfKKQ@mail.gmail.com>
Hello,
On Thu, 22 Jul 2021, Richard Biener via Gcc wrote:
> But how does TLS usage transfer between threads? On the gimple level
> the TLS pointer is not visible and thus we'd happily CSE its address:
Yes. All take-address operations then need to be encoded explicitely with
a non-CSE-able internal function (or so):
&x --> __ifn_get_tls_addr(&x);
(&x in the argument just so that it's clear that it doesn't access the
value at x and to get the current effects of address-taken marking of
ADDR_EXPR).
(Or of course, ADDR_EXPR could be taken as unstable when applied to TLS
decls).
Quite a big hammer IMHO.
Ciao,
Michael.
prev parent reply other threads:[~2021-07-22 16:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-20 14:52 Florian Weimer
2021-07-20 15:31 ` Iain Sandoe
2021-07-21 7:22 ` Thomas Huth
2021-07-22 12:12 ` Richard Biener
2021-07-22 16:01 ` Michael Matz [this message]
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