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Date: Wed, 11 Nov 2015 12:39:56 +0000
From: Will Deacon <will.deacon@....com>
To: Z Lim <zlim.lnx@...il.com>
Cc: Yang Shi <yang.shi@...aro.org>,
Alexei Starovoitov <ast@...nel.org>, daniel@...earbox.net,
Catalin Marinas <catalin.marinas@....com>,
Xi Wang <xi.wang@...il.com>,
LKML <linux-kernel@...r.kernel.org>,
Network Development <netdev@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction
On Wed, Nov 11, 2015 at 12:12:56PM +0000, Will Deacon wrote:
> On Tue, Nov 10, 2015 at 06:45:39PM -0800, Z Lim wrote:
> > On Tue, Nov 10, 2015 at 2:41 PM, Yang Shi <yang.shi@...aro.org> wrote:
> > > aarch64 doesn't have native store immediate instruction, such operation
> >
> > Actually, aarch64 does have "STR (immediate)". For arm64 JIT, we can
> > consider using it as an optimization.
>
> Yes, I'd definitely like to see that in preference to moving via a
> temporary register.
Wait a second, we're both talking rubbish here :) The STR (immediate)
form is referring to the addressing mode, whereas this patch wants to
store an immediate value to memory, which does need moving to a register
first.
So the original patch is fine.
Will
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