From: David Laight <David.Laight@ACULAB.COM>
To: 'Brian Gerst' <brgerst@gmail.com>, "H. Peter Anvin" <hpa@zytor.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
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>,
"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@googlegroups.com"
<clang-built-linux@googlegroups.com>
Subject: RE: [PATCH] x86: bitops: fix build regression
Date: Thu, 7 May 2020 15:09:35 +0000 [thread overview]
Message-ID: <9c701ca55bc442c1899a70896f3ea73e@AcuMS.aculab.com> (raw)
In-Reply-To: <CAMzpN2iCgr0rb=MCYPGMx8tcfLq2qdzv0h7YnX5hkzBB+O7JJQ@mail.gmail.com>
From: Brian Gerst
> Sent: 07 May 2020 14:32
...
> I think the bug this worked around was that the compiler didn't detect
> that CONST_MASK(nr) was also constant and doesn't need to be put into
> a register. The question is does that bug still exist on compiler
> versions we care about?
Hmmm...
That ought to have been fixed instead of worrying about the fact
that an invalid register was used.
Alternatively is there any reason not to use the bts/btc instructions?
Yes, I know they'll do wider accesses, but variable bit numbers do.
It is also possible that the assembler will support constant bit
numbers >= 32 by adding to the address offset.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-05-07 15:09 UTC|newest]
Thread overview: 30+ 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
2020-05-10 11:59 ` 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
2020-05-07 6:18 ` Brian Gerst
2020-05-07 7:02 ` hpa
2020-05-07 13:32 ` Brian Gerst
2020-05-07 15:09 ` David Laight [this message]
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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