Re: [FFmpeg-devel] [PATCH v2] add a configure flag to enabled tree-vecorization with gcc

[Lynne <dev@lynne.ee>]

Aug 8, 2022, 17:25 by jswinney@amazon.com:

> Recent version of gcc improve the automatic vectorization. This flag
> allows adventurous users to enable vectorization. Known problems with
> this are primarily related to inline assembly for x86 and so to address
> those, add a pragma to explicitly disable automatic vectorization for
> those files.
>
> Signed-off-by: Jonathan Swinney <jswinney@amazon.com>
>
> --
>
> Thank you considering this patch. I believe this addresses the primary
> concerns that were raised by my previous submission. There may be more
> files which require the pragma add `-fno-tree-vectorize`, and I welcome
> suggestions. This should strike a compromise, allowing some users to
> enable vectorization while not breaking mainstream builds. This should
> give time to work out additional problems if they arise before enabling
> vectorization more broadly.
>

I dislike this, pretty soon we'll end up with compiler version checks
whenever vectorization breaks.
Either gcc should fix miscompilation, or patches should be sent
to write assembly (which they should be anyway).
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