Re: [PATCH -next v13 19/19] riscv: Enable Vector code to be built

Conor Dooley
2023-01-30T08:15:18Z

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On Mon, Jan 30, 2023 at 03:46:32PM +0800, Andy Chiu wrote:
> On Thu, Jan 26, 2023 at 5:04 AM Conor Dooley <conor@kernel.org> wrote:
> > Firstly, no-implicit-float is a CFLAG, so why add it to march?
> I placed it in march because I thought we need the flag in vdso. And,
> KBUILD_CFLAGS is not enough for vdso. However, I think we don't need
> this flag in vdso since it is run in user space anyway.
> > There is an existing patch on the list for enabling this flag, but I
> > recall Palmer saying that it was not actually needed?
> The flag is needed for clang builds to prevent auto-vectorization from
> using V in the kernel code [1].
>
> > Palmer, do you remember why that was?
> The discussion[2] suggested that we need this flag, IIUC. But somehow
> the patch did make it into the tree.

I know, in [1] I left an R-b as the patch seemed reasonable to me.
Palmer mentioned some reason for not thinking it was actually needed but
not on-list, so I was hoping he'd comment!

And I suppose, it never got any further attention as it isn't needed by
any in-tree code?

> [1]https://lore.kernel.org/all/CAOnJCULtT-y9vo6YhW7bW9XyKRdod-hvFfr02jHVamR_LcsKdA@mail.gmail.com/
> [2]https://lore.kernel.org/all/20221216185012.2342675-1-abdulras@google.com/

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