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Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction

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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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[PATCH 0/2] arm64: bpf: add BPF_ST and BPF_XADD instructions support Yang Shi <yang.shi@linaro.org> - 2015-11-11 00:10 +0100
  [PATCH 1/2] arm64: bpf: add 'store immediate' instruction Yang Shi <yang.shi@linaro.org> - 2015-11-11 00:10 +0100
    Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction Z Lim <zlim.lnx@gmail.com> - 2015-11-11 03:50 +0100
      Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction Will Deacon <will.deacon@arm.com> - 2015-11-11 13:20 +0100
        Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction Will Deacon <will.deacon@arm.com> - 2015-11-11 13:50 +0100
          Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction "Shi, Yang" <yang.shi@linaro.org> - 2015-11-12 20:40 +0100
            Re: [PATCH 1/2] arm64: bpf: add 'store immediate' instruction Z Lim <zlim.lnx@gmail.com> - 2015-11-13 04:50 +0100

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