Re: [FFmpeg-devel] [PATCH v4 2/4] libavutils: Add parse_r helper for MIPS

2020-06-08 Thread jiaxun.y...@flygoat.com


于 2020年6月8日 GMT+08:00 下午4:38:58, Shiyou Yin  写到:
>>-Original Message-
>>From: ffmpeg-devel-boun...@ffmpeg.org 
>>[mailto:ffmpeg-devel-boun...@ffmpeg.org] On Behalf Of
>>Jiaxun Yang
>>Sent: Monday, June 8, 2020 11:30 AM
>>To: ffmpeg-devel@ffmpeg.org
>>Cc: yinshi...@loongson.cn; Jiaxun Yang
>>Subject: [FFmpeg-devel] [PATCH v4 2/4] libavutils: Add parse_r helper for MIPS
>>

[...]

>In inline assembler, we can add asmSymbolicName in Input/ Output Operands, 
>format:
>[ [asmSymbolicName] ] constraint (cExpression)
>[ [asmSymbolicName] ] constraint (cVariableName)

Could you expand it?
I'm not really sure how that related to our case.

I'm trying to use raw opcode in inline assembly and I need
this helper to deal with oprands in raw opcode.

Thanks!

>
>> #endif /* AVCODEC_MIPS_ASMDEFS_H */
>>--
>>2.20.1
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Re: [FFmpeg-devel] [PATCH v4 2/4] libavutils: Add parse_r helper for MIPS

2020-06-08 Thread jiaxun.y...@flygoat.com


于 2020年6月9日 GMT+08:00 下午1:43:58, Shiyou Yin  写到:
>>-Original Message-
>>From: jiaxun.y...@flygoat.com [mailto:jiaxun.y...@flygoat.com]
>>Sent: Tuesday, June 9, 2020 2:03 AM
>>To: FFmpeg development discussions and patches; Shiyou Yin; 'FFmpeg 
>>development discussions and
>>patches'
>>Subject: Re: [FFmpeg-devel] [PATCH v4 2/4] libavutils: Add parse_r helper for 
>>MIPS
>>
>>
>>
>>于 2020年6月8日 GMT+08:00 下午4:38:58, Shiyou Yin  写到:
>>>>-Original Message-
>>>>From: ffmpeg-devel-boun...@ffmpeg.org 
>>>>[mailto:ffmpeg-devel-boun...@ffmpeg.org] On Behalf Of
>>>>Jiaxun Yang
>>>>Sent: Monday, June 8, 2020 11:30 AM
>>>>To: ffmpeg-devel@ffmpeg.org
>>>>Cc: yinshi...@loongson.cn; Jiaxun Yang
>>>>Subject: [FFmpeg-devel] [PATCH v4 2/4] libavutils: Add parse_r helper for 
>>>>MIPS
>>>>
>>
>>[...]
>>
>>>In inline assembler, we can add asmSymbolicName in Input/ Output Operands, 
>>>format:
>>>[ [asmSymbolicName] ] constraint (cExpression)
>>>[ [asmSymbolicName] ] constraint (cVariableName)
>>
>>Could you expand it?
>>I'm not really sure how that related to our case.
>>
>>I'm trying to use raw opcode in inline assembly and I need
>>this helper to deal with oprands in raw opcode.
>>
>>Thanks!
>>
>
>For the raw opcode case, another proposal for your reference.
>static uint32_t read_cpucfg_2(uint32_t reg)
>{
>register uint32_t input __asm__ ("t0") = reg;
>register uint32_t __res __asm__ ("t1") = 0;
>__asm__ volatile(
>".insn \n\t"
>".word (0xc9084918) \n\t"
>);
>return __res;

Actually this is not always safe.
t0 and t1 might be clobbered by compiler optimization.

>}

I need this helper to ensure the register usage is guarded by
compiler's allocation system.

>

-- 
Jiaxun Yang
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