From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: kbuild test robot <lkp@intel.com>,
arnd@arndb.de, Nick Desaulniers <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc: workaround clang codegen bug in dcbz
Date: Mon, 29 Jul 2019 16:52:00 -0500 [thread overview]
Message-ID: <20190729215200.GN31406@gate.crashing.org> (raw)
In-Reply-To: <20190729203246.GA117371@archlinux-threadripper>
On Mon, Jul 29, 2019 at 01:32:46PM -0700, Nathan Chancellor wrote:
> For the record:
>
> https://godbolt.org/z/z57VU7
>
> This seems consistent with what Michael found so I don't think a revert
> is entirely unreasonable.
Try this:
https://godbolt.org/z/6_ZfVi
This matters in non-trivial loops, for example. But all current cases
where such non-trivial loops are done with cache block instructions are
actually written in real assembler already, using two registers.
Because performance matters. Not that I recommend writing code as
critical as memset in C with inline asm :-)
Segher
next prev parent reply other threads:[~2019-07-29 21:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 20:25 [PATCH] powerpc: workaround clang codegen bug in dcbz Nick Desaulniers
2019-07-29 20:32 ` Nathan Chancellor
2019-07-29 20:45 ` Nick Desaulniers
2019-07-29 20:47 ` Nathan Chancellor
2019-07-29 20:49 ` Nick Desaulniers
2019-07-29 21:52 ` Segher Boessenkool [this message]
2019-07-30 7:34 ` Arnd Bergmann
2019-07-30 11:17 ` Michael Ellerman
2019-08-09 18:21 ` [PATCH] powerpc: fix inline asm constraints for dcbz Nick Desaulniers
2019-08-09 18:28 ` Arnd Bergmann
2019-08-09 20:03 ` Christophe Leroy
2019-08-09 20:12 ` Arnd Bergmann
2019-08-09 22:03 ` Nick Desaulniers
2019-08-09 22:10 ` Segher Boessenkool
2019-08-09 22:00 ` Segher Boessenkool
2019-08-09 22:03 ` [PATCH v3] Revert "powerpc: slightly improve cache helpers" Nick Desaulniers
2019-08-10 9:09 ` Michael Ellerman
2019-08-09 21:55 ` [PATCH] powerpc: fix inline asm constraints for dcbz Segher Boessenkool
2019-08-09 20:36 ` Nathan Chancellor
2019-07-30 13:48 ` [PATCH] powerpc: workaround clang codegen bug in dcbz Segher Boessenkool
2019-07-30 14:30 ` Arnd Bergmann
2019-07-30 16:16 ` Segher Boessenkool
2019-07-30 17:07 ` Segher Boessenkool
2019-07-30 18:24 ` Arnd Bergmann
2019-07-30 18:24 ` Arnd Bergmann
2019-07-30 19:35 ` Segher Boessenkool
2019-07-30 5:31 ` Christophe Leroy
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