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From: Segher Boessenkool <segher@kernel.crashing.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Paul Mackerras <paulus@samba.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	kbuild test robot <lkp@intel.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH] powerpc: fix inline asm constraints for dcbz
Date: Fri, 9 Aug 2019 17:10:52 -0500	[thread overview]
Message-ID: <20190809221052.GP31406@gate.crashing.org> (raw)
In-Reply-To: <CAK8P3a1AwmAe+PpHTRmN153fhG4ZkF_pb+240rj1ZAg-S6SKeg@mail.gmail.com>

On Fri, Aug 09, 2019 at 10:12:56PM +0200, Arnd Bergmann wrote:
> @@ -106,7 +106,7 @@ static inline u##size name(const volatile u##size
> __iomem *addr)    \
>  {                                                                      \
>         u##size ret;                                                    \
>         __asm__ __volatile__("sync;"#insn" %0,%y1;twi 0,%0,0;isync"     \
> -               : "=r" (ret) : "Z" (*addr) : "memory");                 \
> +               : "=r" (ret) : "m" (*addr) : "memory");                 \
>         return ret;                                                     \
>  }

That will no longer compile something like
  u8 *p;
  u16 x = in_le16(p + 12);
(you'll get something like "invalid %y value, try using the 'Z' constraint").

So then you remove the %y, but that makes you get something like
  sync;lhbrx 3,12(3);twi 0,3,0;isync
which is completely wrong.


Segher

  parent reply	other threads:[~2019-08-09 22:11 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 [this message]
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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