From: Nathan Chancellor <natechancellor@gmail.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: arnd@arndb.de, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org, kbuild test robot <lkp@intel.com>
Subject: Re: [PATCH] powerpc: fix inline asm constraints for dcbz
Date: Fri, 9 Aug 2019 13:36:45 -0700 [thread overview]
Message-ID: <20190809203645.GA85763@archlinux-threadripper> (raw)
In-Reply-To: <20190809182106.62130-1-ndesaulniers@google.com>
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On Fri, Aug 09, 2019 at 11:21:05AM -0700, Nick Desaulniers wrote:
> The input parameter is modified, so it should be an output parameter
> with "=" to make it so that a copy of the input is not made by Clang.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42762
> Link: https://gcc.gnu.org/onlinedocs/gcc/Modifiers.html#Modifiers
> Link: https://github.com/ClangBuiltLinux/linux/issues/593
> Link: https://godbolt.org/z/QwhZXi
> Link: https://lore.kernel.org/lkml/20190721075846.GA97701@archlinux-threadripper/
> Fixes: 6c5875843b87 ("powerpc: slightly improve cache helpers")
> Debugged-by: Nathan Chancellor <natechancellor@gmail.com>
> Reported-by: Nathan Chancellor <natechancellor@gmail.com>
> Reported-by: kbuild test robot <lkp@intel.com>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
I applied this patch as well as a revert of the original patch and both
clang and GCC appear to generate the same code; I think a straight
revert would be better.
Crude testing script and the generated files attached.
Cheers,
Nathan
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next prev parent reply other threads:[~2019-08-09 20:38 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 [this message]
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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