[PATCH] riscv: Optimize memset
zhangfei
zhang_fei_0403 at 163.com
Tue May 9 20:52:43 PDT 2023
From: zhangfei <zhangfei at nj.iscas.ac.cn>
On Tue, May 09, 2023 11:16:33AM +0200, Andrew Jones wrote:
> On Tue, May 09, 2023 at 10:22:07AM +0800, zhangfei wrote:
> >
> > Hi,
> >
> > I filled head and tail with minimal branching. Each conditional ensures that
> > all the subsequently used offsets are well-defined and in the dest region.
>
> I know. You trimmed my comment, so I'll quote myself, here
>
> """
> After the check of a2 against 6 above we know that offsets 6(t0)
> and -7(a3) are safe. Are we trying to avoid too may redundant
> stores with these additional checks?
> """
>
> So, again. Why the additional check against 8 above and, the one you
> trimmed, checking 10?
Hi,
These additional checks are to avoid too many redundant stores.
Adding a check for more than 8 bytes is because after the loop
segment '3' comes out, the remaining bytes are less than 8 bytes,
which also avoids redundant stores.
Thanks,
Fei Zhang
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