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From: "H. Peter Anvin" <hpa@zytor.com>
To: Nick Desaulniers <ndesaulniers@google.com>,
	Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	stable <stable@vger.kernel.org>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	"kernelci . org bot" <bot@kernelci.org>,
	Andy Shevchenko <andriy.shevchenko@intel.com>,
	Ilie Halip <ilie.halip@gmail.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	Marco Elver <elver@google.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Daniel Axtens <dja@axtens.net>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH] x86: bitops: fix build regression
Date: Fri, 8 May 2020 10:31:36 -0700	[thread overview]
Message-ID: <8f53b69e-86cc-7ff9-671e-5e0a67ff75a2@zytor.com> (raw)
In-Reply-To: <CAKwvOd=hVKrFU+imSGeX+MEKMpW97gE7bzn1C637qdns9KSnUA@mail.gmail.com>

On 2020-05-08 10:21, Nick Desaulniers wrote:
>>
>> One last suggestion.  Add the "b" modifier to the mask operand: "orb
>> %b1, %0".  That forces the compiler to use the 8-bit register name
>> instead of trying to deduce the width from the input.
> 
> Ah right: https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#x86Operandmodifiers
> 
> Looks like that works for both compilers.  In that case, we can likely
> drop the `& 0xff`, too.  Let me play with that, then I'll hopefully
> send a v3 today.
> 

Good idea. I requested a while ago that they document these modifiers; they
chose not to document them all which in some ways is good; it shows what they
are willing to commit to indefinitely.

	-hpa

  reply	other threads:[~2020-05-08 17:32 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-05 17:44 [PATCH] x86: bitops: fix build regression Nick Desaulniers
2020-05-05 18:07 ` hpa
2020-05-05 18:22   ` Nick Desaulniers
2020-05-07 11:34   ` Peter Zijlstra
2020-05-07 14:00     ` Brian Gerst
2020-05-07 19:19       ` Nick Desaulniers
2020-05-07 22:29         ` Nick Desaulniers
2020-05-08  1:57           ` Brian Gerst
2020-05-08 17:21             ` Nick Desaulniers
2020-05-08 17:31               ` H. Peter Anvin [this message]
2020-05-08 18:05                 ` [PATCH v3] " Nick Desaulniers
2020-05-08 18:08                   ` Nick Desaulniers
2020-05-08 18:22                   ` Brian Gerst
2020-05-08 18:28                     ` [PATCH v4] " Nick Desaulniers
2020-05-08 18:32                       ` [PATCH v5] " Nick Desaulniers
2020-05-08 20:28                         ` Nathan Chancellor
2020-05-08 23:47                           ` Jesse Brandeburg
2020-05-09  4:44                             ` Sedat Dilek
2020-05-09 12:20                         ` Andy Shevchenko
2020-05-09 15:43                           ` Brian Gerst
2020-05-11 17:22                           ` Nick Desaulniers
2020-05-10 13:54                         ` David Laight
2020-05-11 18:52                         ` Brian Gerst
2020-05-14 23:47                           ` Nick Desaulniers
2020-05-10 11:59                 ` [PATCH] " David Laight
2020-05-10 12:33                   ` hpa
2020-05-07 19:29     ` hpa
2020-05-06  4:30 ` Nathan Chancellor
2020-05-06  9:22   ` Sedat Dilek
2020-05-06 15:41   ` Nathan Chancellor
2020-05-06 16:37   ` Nick Desaulniers
2020-05-06 16:55     ` Ilie Halip
2020-05-06 17:05       ` [PATCH v2] " Nick Desaulniers
2020-05-07  6:18 ` [PATCH] " Brian Gerst
2020-05-07  7:02   ` hpa
2020-05-07 13:32     ` Brian Gerst
2020-05-07 15:09       ` David Laight
2020-05-07 19:31         ` hpa
2020-05-07 19:29       ` hpa
2020-05-07  7:44   ` David Laight
2020-05-07  7:59     ` hpa
2020-05-07  8:35       ` David Laight
2020-05-07  8:38         ` hpa
2020-05-07  9:17     ` Andy Shevchenko
2020-05-07 19:22   ` Nick Desaulniers

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