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Message-ID: <d23e1b70-7ac3-49cd-8d5f-1dedc0108603@zytor.com>
Date: Sun, 21 Jan 2024 15:21:54 -0800
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Subject: Re: [PATCH 1/2] x86: Remove dynamic NOP selection
To: Thorsten Glaser <tg@debian.org>
Cc: Peter Zijlstra <peterz@infradead.org>, x86@kernel.org, rostedt@goodmis.org,
        torvalds@linuxfoundation.org, linux-kernel@vger.kernel.org,
        linux-toolchains@vger.kernel.org, jpoimboe@redhat.com,
        alexei.starovoitov@gmail.com, mhiramat@kernel.org
References: <20210312113253.305040674@infradead.org>
 <20210312115749.065275711@infradead.org>
 <Pine.BSM.4.64L.2401200654480.19429@herc.mirbsd.org>
 <CE53F232-3D2D-4910-94B4-A4304F5990C7@zytor.com>
 <Pine.BSM.4.64L.2401201652490.29203@herc.mirbsd.org>
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From: "H. Peter Anvin" <hpa@zytor.com>
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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