From: Matteo Croce <mcroce@linux.microsoft.com>
To: David Laight <David.Laight@aculab.com>
Cc: Christoph Hellwig <hch@infradead.org>,
"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: Wed, 23 Jun 2021 00:53:35 +0200 [thread overview]
Message-ID: <CAFnufp06+s43z5SxL48LB73=GdzYFiq578MCHZ_NMUNZkwdo9g@mail.gmail.com> (raw)
In-Reply-To: <17bb90eef20145cd9cca1b8e72a514ad@AcuMS.aculab.com>
On Tue, Jun 22, 2021 at 10:19 AM David Laight <David.Laight@aculab.com> wrote:
>
> 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) {
>
This way we'll lose the remainder, as count is used at the end to copy
the leftover.
Anyway, both bytes_long and mask are constant, I doubt they get summed
at every cycle.
> Next is to shorten the variable names!
>
> David
>
--
per aspera ad upstream
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next prev parent reply other threads:[~2021-06-22 22:54 UTC|newest]
Thread overview: 23+ 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 ` [PATCH v3 1/3] riscv: optimized memcpy Matteo Croce
2021-06-18 14:06 ` kernel test robot
2021-06-21 14:26 ` Christoph Hellwig
2021-06-22 8:19 ` David Laight
2021-06-22 22:53 ` Matteo Croce [this message]
2021-06-22 22:00 ` Matteo Croce
2021-06-22 0:14 ` Nick Kossifidis
2021-06-22 23:35 ` Matteo Croce
2021-06-23 9:48 ` Nick Kossifidis
2021-06-17 15:27 ` [PATCH v3 2/3] riscv: optimized memmove Matteo Croce
2021-06-21 14:28 ` Christoph Hellwig
2021-06-22 0:46 ` Nick Kossifidis
2021-06-30 4:40 ` kernel test robot
2021-06-17 15:27 ` [PATCH v3 3/3] riscv: optimized memset Matteo Croce
2021-06-21 14:32 ` Christoph Hellwig
2021-06-22 1:07 ` Nick Kossifidis
2021-06-22 8:38 ` David Laight
2021-06-23 1:14 ` Matteo Croce
2021-06-23 9:05 ` David Laight
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 2:39 ` Guo Ren
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