[FFmpeg-devel] [PATCH] Revert "libavcodec/mips: Fix specification of instruction name"

[yinshiyou-hf at loongson.cn]

> -----原始邮件-----
> 发件人: "Jiaxun Yang" <jiaxun.yang at flygoat.com>
> 发送时间: 2021-07-21 17:39:22 (星期三)
> 收件人: ffmpeg-devel at ffmpeg.org
> 抄送: yinshiyou-hf at loongson.cn, "Jin Bo" <jinbo at loongson.cn>, "Jiaxun Yang" <jiaxun.yang at flygoat.com>
> 主题: [FFmpeg-devel] [PATCH] Revert "libavcodec/mips: Fix specification of instruction name"
> 
> This reverts commit ebedd26eefe2ff4bbf5a358907c4e8e4b0d62eae.
> 
> The original commit states that "gcc supports both of them,
> clang only supports the second type", it's obviousely not ture.
> 
> Error: opcode not supported on this processor: loongson3a(mips64r2) `pxor $f3,$f3,$f3'
> 
> Tested with latest GCC11 and binutils 2.37.
> 
> The statement is not true. I guess you may have a internal toolchain modified
> for this purpose, but you're not the sole user of FFmpeg, you're breaking
> other users like Debian. Also I can't find clang with Loongson extention
> support every where.
> 
> I'm reverting this for now. If you would like to implement it, another approach
> could be make it as marco in mmiutils.h and filter it with #if define(__clang__).
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang at flygoat.com>
> Cc: Jin Bo <jinbo at loongson.cn>
> Cc: yinshiyou-hf at loongson.cn

Thank you for your feedback, following are my opinions:
1）according to the instruction mannul, we should use 'pxor' to operate float register.
2) MMI is loongson media extention，compiler from upstream not supported yet is true.
 If you are using FFmpeg on loongson platform, you can try to get compiler from 
 http://www.loongnix.org/index.php/GCC or use loongson repository download.
 Loongnix-1.0 :http://ftp.loongnix.org/os/loongnix/1.0/os/
 Loongnix-20-mips64el:http://ftp.loongnix.org/os/loongnix/20/mips64el
3) If you are using on other mips platform which MMI is unsupported, and MMI havn't disabled automaticlly.
 we will fix it soon.
4) on the safe side, I suggest to add pxor instruction check in configure check.
</jinbo at loongson.cn></jiaxun.yang at flygoat.com></jiaxun.yang at flygoat.com></jinbo at loongson.cn></jiaxun.yang at flygoat.com>