Re: [FFmpeg-devel] [PATCH] lavc/hevcdsp_qpel_neon: using movi.16b instead of movi.2d - 徐福隆 via ffmpeg-devel

From: "徐福隆 via ffmpeg-devel" <ffmpeg-devel@ffmpeg.org>
To: =?gb18030?B?RkZtcGVnIGRldmVsb3BtZW50IGRpc2N1c3Npb25zIGFuZCBwYXRjaGVz?=
	<ffmpeg-devel@ffmpeg.org>
Cc: =?gb18030?B?0Oy4o8Kh?= <839789740@qq.com>,
	=?gb18030?B?bWFydGlu?= <martin@martin.st>
Subject: Re: [FFmpeg-devel] [PATCH] lavc/hevcdsp_qpel_neon: using movi.16b instead of movi.2d
Date: Wed, 29 Nov 2023 18:01:57 +0800
Message-ID: <tencent_AA0E4645F0E56CCD3C9E653DA1AB6CCA1807@qq.com> (raw)
In-Reply-To: <e154274-eea-8838-3d13-bc85d794ebe0@martin.st>

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Thank you for your reading and explaining carefully, Martin.
Yes, you are right. I build with iOS 13.0, and FFmpeg 6.0.
It seems that there is no ".arch" directive in asm.S.
That is to say, it isn't a newest version.

------------------&nbsp;Original&nbsp;------------------
From:                                                                                                                        "FFmpeg development discussions and patches"                                                                                    <martin@martin.st&gt;;
Date:&nbsp;Tue, Nov 28, 2023 09:57 PM
To:&nbsp;"xufuji456 via ffmpeg-devel"<ffmpeg-devel@ffmpeg.org&gt;;
Cc:&nbsp;"Ðì¸£Â¡"<839789740@qq.com&gt;;
Subject:&nbsp;Re: [FFmpeg-devel] [PATCH] lavc/hevcdsp_qpel_neon: using movi.16b instead of movi.2d

Hi,&nbsp;

On Wed, 15 Nov 2023, xufuji456 via ffmpeg-devel wrote:

&gt; Building iOS platform with arm64, the compiler has a warning: 
&gt; "instruction movi.2d with immediate #0 may not function correctly on 
&gt; this CPU, converting to movi.16b"

The change is correct and something we should do. However since 
fb1b88af77cd39034cef4b6d08af79496cd75ed8, our asm.S starts with an ".arch" 
directive, and that silences this warning, so I wonder how you've run into 
it or tested it. (I presume you've run into it with an older version, then 
tried to find all cases of this instruction in the codebase and changed 
those?)

(This warning is something that only is triggered when building for iOS, 
not macOS, due to a bug in early iPhone CPUs - see 
https://github.com/llvm/llvm-project/commit/9097a07e4e83b9f394598d53557247277b064b09.)

Anyway, the change looks good, so I'll push it.

// Martin

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