Message-ID: <5644E97B.6050203@linaro.org>
Date: Thu, 12 Nov 2015 11:33:15 -0800
From: "Shi, Yang" <yang.shi@linaro.org>
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To: Will Deacon <will.deacon@arm.com>, Z Lim <zlim.lnx@gmail.com>
CC: Alexei Starovoitov <ast@kernel.org>, daniel@iogearbox.net,
        Catalin Marinas <catalin.marinas@arm.com>, Xi Wang <xi.wang@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        linaro-kernel@lists.linaro.org
Subject: Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction
References: <1447195301-16757-1-git-send-email-yang.shi@linaro.org> <1447195301-16757-2-git-send-email-yang.shi@linaro.org> <CABg9mct-_AF9+kvZ0OG_JTMHkfj+OEsR2vonrxF=yD-yA6ihQw@mail.gmail.com> <20151111121256.GI9562@arm.com> <20151111123955.GK9562@arm.com>
In-Reply-To: <20151111123955.GK9562@arm.com>
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On 11/11/2015 4:39 AM, Will Deacon wrote:
> 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@linaro.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.

Yes, the immediate means immediate offset for addressing index. Doesn't 
mean to store immediate to memory.

I don't think any load-store architecture has store immediate instruction.

Thanks,
Yang

>
> So the original patch is fine.
>
> Will
>

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