linux-kernel - RE: [PATCH v3 1/3] riscv: optimized memcpy

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Date:   Tue, 22 Jun 2021 08:19:13 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christoph Hellwig' <hch@...radead.org>,
        Matteo Croce <mcroce@...ux.microsoft.com>
CC:     "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atish.patra@....com>,
        "Emil Renner Berthing" <kernel@...il.dk>,
        Akira Tsukamoto <akira.tsukamoto@...il.com>,
        "Drew Fustini" <drew@...gleboard.org>,
        Bin Meng <bmeng.cn@...il.com>, Guo Ren <guoren@...nel.org>
Subject: RE: [PATCH v3 1/3] riscv: optimized memcpy

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

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