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From: Nick Desaulniers <ndesaulniers@google.com>
To: Brian Gerst <brgerst@gmail.com>
Cc: 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>,
	"H. Peter Anvin" <hpa@zytor.com>, Marco Elver <elver@google.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.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: Thu, 7 May 2020 12:22:30 -0700	[thread overview]
Message-ID: <CAKwvOdkBaxyOiO8+_cdBenkOj5cqcn9OhThOLmbt1uMyTW1P6g@mail.gmail.com> (raw)
In-Reply-To: <CAMzpN2idWF2_4wtPebM2B2HVyksknr9hAqK8HJi_vjQ06bgu2g@mail.gmail.com>

On Wed, May 6, 2020 at 11:18 PM Brian Gerst <brgerst@gmail.com> wrote:
>
> I think a better fix would be to make CONST_MASK() return a u8 value
> rather than have to cast on every use.
>
> Also I question the need for the "q" constraint.  It was added in
> commit 437a0a54 as a workaround for GCC 3.4.4.  Now that the minimum
> GCC version is 4.6, is this still necessary?

TL;DR yes

ah, thanks for the git archeology, it's useful.  I don't think this is
a compiler bug however, just the compiler being more strict that the
`b` suffix on `orb` requires a 8b register operand.  For 32b x86, `q`
asm constraint is required, because not all GPR's had lower 8b
register aliases, as Arnd found and HPA noted as well.

I like your suggested change to CONST_MASK, and will send that in a bit.
-- 
Thanks,
~Nick Desaulniers

      parent reply	other threads:[~2020-05-07 19:22 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
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 [this message]

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