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From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@infradead.org>,
	Matteo Croce <mcroce@linux.microsoft.com>
Cc: "linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Atish Patra <atish.patra@wdc.com>,
	"Emil Renner Berthing" <kernel@esmil.dk>,
	Akira Tsukamoto <akira.tsukamoto@gmail.com>,
	"Drew Fustini" <drew@beagleboard.org>,
	Bin Meng <bmeng.cn@gmail.com>, Guo Ren <guoren@kernel.org>
Subject: RE: [PATCH v3 1/3] riscv: optimized memcpy
Date: Tue, 22 Jun 2021 08:19:13 +0000	[thread overview]
Message-ID: <17bb90eef20145cd9cca1b8e72a514ad@AcuMS.aculab.com> (raw)
In-Reply-To: <YNChl0tkofSGzvIX@infradead.org>

From: Christoph Hellwig
> Sent: 21 June 2021 15:27
...
> > +		for (next = s.ulong[0]; count >= bytes_long + mask; count -= bytes_long) {
> 
> Please avoid the pointlessly overlong line.  And (just as a matter of
> personal preference) I find for loop that don't actually use a single
> iterator rather confusing.  Wjy not simply:
> 
> 		next = s.ulong[0];
> 		while (count >= bytes_long + mask) {
> 			...
> 			count -= bytes_long;
> 		}

My fist attack on long 'for' statements is just to move the
initialisation to the previous line.
Then make sure there is nothing in the comparison that needs
to be calculated every iteration.
I suspect you can subtract 'mask' from 'count'.
Giving:
		count -= mask;
		next = s.ulong[0];
		for (;; count > bytes_long; count -= bytes_long) {

Next is to shorten the variable names!

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


WARNING: multiple messages have this Message-ID (diff)
From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@infradead.org>,
	Matteo Croce <mcroce@linux.microsoft.com>
Cc: "linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Atish Patra <atish.patra@wdc.com>,
	"Emil Renner Berthing" <kernel@esmil.dk>,
	Akira Tsukamoto <akira.tsukamoto@gmail.com>,
	"Drew Fustini" <drew@beagleboard.org>,
	Bin Meng <bmeng.cn@gmail.com>, Guo Ren <guoren@kernel.org>
Subject: RE: [PATCH v3 1/3] riscv: optimized memcpy
Date: Tue, 22 Jun 2021 08:19:13 +0000	[thread overview]
Message-ID: <17bb90eef20145cd9cca1b8e72a514ad@AcuMS.aculab.com> (raw)
In-Reply-To: <YNChl0tkofSGzvIX@infradead.org>

From: Christoph Hellwig
> Sent: 21 June 2021 15:27
...
> > +		for (next = s.ulong[0]; count >= bytes_long + mask; count -= bytes_long) {
> 
> Please avoid the pointlessly overlong line.  And (just as a matter of
> personal preference) I find for loop that don't actually use a single
> iterator rather confusing.  Wjy not simply:
> 
> 		next = s.ulong[0];
> 		while (count >= bytes_long + mask) {
> 			...
> 			count -= bytes_long;
> 		}

My fist attack on long 'for' statements is just to move the
initialisation to the previous line.
Then make sure there is nothing in the comparison that needs
to be calculated every iteration.
I suspect you can subtract 'mask' from 'count'.
Giving:
		count -= mask;
		next = s.ulong[0];
		for (;; count > bytes_long; count -= bytes_long) {

Next is to shorten the variable names!

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


_______________________________________________
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http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2021-06-22  8:19 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-17 15:27 [PATCH v3 0/3] riscv: optimized mem* functions Matteo Croce
2021-06-17 15:27 ` Matteo Croce
2021-06-17 15:27 ` [PATCH v3 1/3] riscv: optimized memcpy Matteo Croce
2021-06-17 15:27   ` Matteo Croce
2021-06-18 14:06   ` kernel test robot
2021-06-18 14:06     ` kernel test robot
2021-06-18 14:06     ` kernel test robot
2021-06-21 14:26   ` Christoph Hellwig
2021-06-21 14:26     ` Christoph Hellwig
2021-06-22  8:19     ` David Laight [this message]
2021-06-22  8:19       ` David Laight
2021-06-22 22:53       ` Matteo Croce
2021-06-22 22:53         ` Matteo Croce
2021-06-22 22:00     ` Matteo Croce
2021-06-22 22:00       ` Matteo Croce
2021-06-22  0:14   ` Nick Kossifidis
2021-06-22  0:14     ` Nick Kossifidis
2021-06-22 23:35     ` Matteo Croce
2021-06-22 23:35       ` Matteo Croce
2021-06-23  9:48       ` Nick Kossifidis
2021-06-23  9:48         ` Nick Kossifidis
2021-06-17 15:27 ` [PATCH v3 2/3] riscv: optimized memmove Matteo Croce
2021-06-17 15:27   ` Matteo Croce
2021-06-21 14:28   ` Christoph Hellwig
2021-06-21 14:28     ` Christoph Hellwig
2021-06-22  0:46   ` Nick Kossifidis
2021-06-22  0:46     ` Nick Kossifidis
2021-06-30  4:40   ` kernel test robot
2021-06-30  4:40     ` kernel test robot
2021-06-30  4:40     ` kernel test robot
2021-06-17 15:27 ` [PATCH v3 3/3] riscv: optimized memset Matteo Croce
2021-06-17 15:27   ` Matteo Croce
2021-06-21 14:32   ` Christoph Hellwig
2021-06-21 14:32     ` Christoph Hellwig
2021-06-22  1:07   ` Nick Kossifidis
2021-06-22  1:07     ` Nick Kossifidis
2021-06-22  8:38     ` David Laight
2021-06-22  8:38       ` David Laight
2021-06-23  1:14       ` Matteo Croce
2021-06-23  1:14         ` Matteo Croce
2021-06-23  9:05         ` David Laight
2021-06-23  9:05           ` David Laight
2021-06-23  0:08     ` Matteo Croce
2021-06-23  0:08       ` Matteo Croce
2021-06-22  1:09 ` [PATCH v3 0/3] riscv: optimized mem* functions Nick Kossifidis
2021-06-22  1:09   ` Nick Kossifidis
2021-06-22  2:39   ` Guo Ren
2021-06-22  2:39     ` Guo Ren

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