Re: [FFmpeg-devel] [PATCH] RISC-V:update ff_get_cpu_flags_riscv for RVV

[daichengrong <daichengrong@iscas.ac.cn>]

hi,

The reply email was mistakenly classified as spam, resulting in not 
being seen in time.

Late reply.

在 2025/3/15 12:03:09, Rémi Denis-Courmont :
> Hi,
>
> Le 14 mars 2025 17:32:57 GMT+07:00, daichengrong@iscas.ac.cn a écrit :
>> From: daichengrong <daichengrong@iscas.ac.cn>
>>
>> Availability of RVV and ZVBB should be determined with dl_hwcap.
> No. That's completely superfluous since we already check for kernel support with hwprobe().
No. If the operating system does not enable dl_hwcap support for rvv, an 
illegal instruction exception will be reported , even if the hardware 
and kernel support RVV.
> And we can't check for Zb* and Zv* with hwcap anyhow.
>
>> As those extensions rely on vector registers, kernel vector support
>> is required to save the state of context switching.
> No. Kernel context switching is already ascertained.
No. The kernel will not save and restore vector registers if the program 
does not use vector instructions.
> And we don't care about libc context support, since vectors are clobbered by function calls, e.g. for long jumps or ucontext.
I'm confused about this
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