From: David Laight <David.Laight@ACULAB.COM>
To: "'Hayes Wang'" <hayeswang@realtek.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Cc: nic_swsd <nic_swsd@realtek.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: RE: [PATCH net-next] r8152: simply the arguments
Date: Fri, 17 Mar 2017 11:08:05 +0000 [thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6DCFFB3ABD@AcuExch.aculab.com> (raw)
In-Reply-To: <0835B3720019904CB8F7AA43166CEEB201A32FCB@RTITMBSV06.realtek.com.tw>
From: Hayes Wang
> Sent: 17 March 2017 03:00
> To: David Laight; netdev@vger.kernel.org
> Cc: nic_swsd; linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org
> Subject: RE: [PATCH net-next] r8152: simply the arguments
>
> David Laight [mailto:David.Laight@ACULAB.COM]
> > Sent: Thursday, March 16, 2017 10:28 PM
> [...]
> > If you are really lucky the compiler will optimise it away.
> > Otherwise it will generate another local variable and possibly
> > a register spill to stack.
>
> However, I could reduce the time for calculating the address,
> because I only calculate it once and save the result to a variable.
> Right?
address you want is just an offset from another pointer that is
commonly used and ought to be assigned to a register variable.
The offset can be added by the instruction that puts the value into
the register used for the first function argument.
So 'saving' it in another variable is extra work.
David
prev parent reply other threads:[~2017-03-17 11:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-16 6:27 [PATCH net-next] r8152: simply the arguments Hayes Wang
2017-03-16 6:32 ` [PATCH v2 " Hayes Wang
2017-03-16 17:14 ` David Miller
2017-03-16 17:14 ` David Miller
2017-03-16 14:28 ` [PATCH " David Laight
2017-03-17 2:59 ` Hayes Wang
2017-03-17 11:08 ` David Laight [this message]
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