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Message-ID: <d23e1b70-7ac3-49cd-8d5f-1dedc0108603@zytor.com>
Date: Sun, 21 Jan 2024 15:21:54 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Thorsten Glaser <tg@...ian.org>
Cc: Peter Zijlstra <peterz@...radead.org>, x86@...nel.org, rostedt@...dmis.org,
torvalds@...uxfoundation.org, linux-kernel@...r.kernel.org,
linux-toolchains@...r.kernel.org, jpoimboe@...hat.com,
alexei.starovoitov@...il.com, mhiramat@...nel.org
Subject: Re: [PATCH 1/2] x86: Remove dynamic NOP selection
On 1/20/24 08:53, Thorsten Glaser wrote:
> H. Peter Anvin dixit:
>
>> %eiz was something that binutils used to put in when disassembling
>> certain redundant encodings with SIB at some point.
>
> Ah, fair enough. Maybe this could be added as one more line in
> the comment or something.
>
I think "proper" gas syntax would be 0(%esi,,1), although that doesn't
assemble either (I don't believe there is a way to get gas to actually
generate this sequence.)
But yes, with all even remotely recent CPUs all actually handling nopl
properly, this isn't relevant anymore.
-hpa
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