Date: Tue, 18 Sep 2012 17:03:21 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Konstantin Belousov <kostikbel@gmail.com> Cc: attilio@freebsd.org, arch@freebsd.org Subject: Re: Aliasing issue with TAILQ on ppc64 ? Message-ID: <22549.1347987801@critter.freebsd.dk> In-Reply-To: Your message of "Tue, 18 Sep 2012 19:48:26 %2B0300." <20120918164826.GI37286@deviant.kiev.zoral.com.ua>
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In message <20120918164826.GI37286@deviant.kiev.zoral.com.ua>, Konstantin Belou sov writes: >[...] compiler must not reorder accesses which >provably causes change in the behaviour. As I said, I'm not entirely sure why this goes wrong, and I didn't feel like learning PPC64 assembler constraints just now to find out. My understanding is that the cast from entry->head effectively obscures from the compiler what goes on in this case, making that optimization fair game. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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