From: David Laight <David.Laight@ACULAB.COM>
To: 'Niklas Schnelle' <schnelle@linux.ibm.com>,
'Jason Gunthorpe' <jgg@nvidia.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"David S. Miller" <davem@davemloft.net>,
"Eric Dumazet" <edumazet@google.com>,
Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
"Heiko Carstens" <hca@linux.ibm.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Justin Stitt <justinstitt@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Leon Romanovsky <leon@kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
"llvm@lists.linux.dev" <llvm@lists.linux.dev>,
Ingo Molnar <mingo@redhat.com>, Bill Wendling <morbo@google.com>,
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Paolo Abeni <pabeni@redhat.com>,
Salil Mehta <salil.mehta@huawei.com>,
Jijie Shao <shaojijie@huawei.com>,
Sven Schnelle <svens@linux.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
"x86@kernel.org" <x86@kernel.org>,
Yisen Zhuang <yisen.zhuang@huawei.com>,
Arnd Bergmann <arnd@arndb.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Leon Romanovsky <leonro@mellanox.com>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Michael Guralnik <michaelgur@mellanox.com>,
"patches@lists.linux.dev" <patches@lists.linux.dev>,
Will Deacon <will@kernel.org>
Subject: RE: [PATCH 4/6] arm64/io: Provide a WC friendly __iowriteXX_copy()
Date: Fri, 23 Feb 2024 11:05:29 +0000 [thread overview]
Message-ID: <3227d5224a9745e388738d016fdae87a@AcuMS.aculab.com> (raw)
In-Reply-To: <61931c626d9bc54369d73fda8f8ee59bbb5e95bc.camel@linux.ibm.com>
...
> > > > > + if ((_count % 8) >= 4) {
> > > >
> > > > If (_count & 4) {
> > >
> > > That would be obfuscating, IMHO. The compiler doesn't need such things
> > > to generate optimal code.
> >
> > Try it: https://godbolt.org/z/EvvGrTxv3
> > And it isn't that obfuscated - no more so than your version.
>
> The godbolt link does "n % 8 > 4" instead of "... >= 4" as in Jason's
> original code. With ">=" the compiled code matches that for "n & 4".
Bugger :-)
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
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next prev parent reply other threads:[~2024-02-23 11:05 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-21 1:17 [PATCH 0/6] Fix mlx5 write combining support on new ARM64 cores Jason Gunthorpe
2024-02-21 1:17 ` [PATCH 1/6] x86: Stop using weak symbols for __iowrite32_copy() Jason Gunthorpe
2024-02-21 1:17 ` [PATCH 2/6] s390: Implement __iowrite32_copy() Jason Gunthorpe
2024-02-21 1:17 ` [PATCH 3/6] s390: Stop using weak symbols for __iowrite64_copy() Jason Gunthorpe
2024-02-21 1:17 ` [PATCH 4/6] arm64/io: Provide a WC friendly __iowriteXX_copy() Jason Gunthorpe
2024-02-21 19:22 ` Will Deacon
2024-02-21 23:28 ` Jason Gunthorpe
2024-02-22 22:05 ` David Laight
2024-02-22 22:36 ` Jason Gunthorpe
2024-02-23 9:07 ` David Laight
2024-02-23 11:01 ` Niklas Schnelle
2024-02-23 11:05 ` David Laight [this message]
2024-02-23 12:53 ` Jason Gunthorpe
2024-02-23 11:38 ` Niklas Schnelle
2024-02-23 12:19 ` David Laight
2024-02-23 13:03 ` Jason Gunthorpe
2024-02-23 13:52 ` David Laight
2024-02-23 14:44 ` Jason Gunthorpe
2024-02-23 12:58 ` Jason Gunthorpe
2024-02-23 16:35 ` Niklas Schnelle
2024-02-23 17:05 ` Jason Gunthorpe
2024-02-27 10:37 ` Catalin Marinas
2024-02-28 23:06 ` Jason Gunthorpe
2024-02-29 10:24 ` Catalin Marinas
2024-02-29 13:28 ` Jason Gunthorpe
2024-02-29 10:33 ` Catalin Marinas
2024-02-29 13:29 ` Jason Gunthorpe
2024-03-01 18:52 ` Catalin Marinas
2024-02-21 1:17 ` [PATCH 5/6] net: hns3: Remove io_stop_wc() calls after __iowrite64_copy() Jason Gunthorpe
2024-02-22 0:57 ` Jijie Shao
2024-02-21 1:17 ` [PATCH 6/6] IB/mlx5: Use __iowrite64_copy() for write combining stores Jason Gunthorpe
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