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From: Segher Boessenkool <segher@kernel.crashing.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: kbuild test robot <lkp@intel.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Paul Mackerras <paulus@samba.org>,
	Nathan Chancellor <natechancellor@gmail.com>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] powerpc: workaround clang codegen bug in dcbz
Date: Tue, 30 Jul 2019 12:07:28 -0500	[thread overview]
Message-ID: <20190730170728.GQ31406@gate.crashing.org> (raw)
In-Reply-To: <20190730161637.GP31406@gate.crashing.org>

On Tue, Jul 30, 2019 at 11:16:37AM -0500, Segher Boessenkool wrote:
> in_le32 and friends?  Yeah, huh.  If LLVM copies that to the stack as
> well, its (not byte reversing) read will be atomic just fine, so things
> will still work correctly.
> 
> The things defined with DEF_MMIO_IN_D (instead of DEF_MMIO_IN_X) do not
> look like they will work correctly if an update form address is chosen,
> but that won't happen because the constraint is "m" instead of "m<>",
> making the %Un pretty useless (it will always be the empty string).

Btw, this is true since GCC 4.8; before 4.8, plain "m" *could* have an
automodify (autoinc, autodec, etc.) side effect.  What is the minimum
GCC version required, these days?

https://gcc.gnu.org/PR44492
https://gcc.gnu.org/r161328


Segher

  reply	other threads:[~2019-07-30 17:09 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
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 [this message]
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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