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

From: Shi, Yang
Date: Thu Nov 12 2015 - 14:33:23 EST

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@xxxxxxxxxx> 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

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.


So the original patch is fine.


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