Re: [PATCH 01/12] x86_64: memset_user()

Matthew Wilcox
2018-12-21T21:07:35Z

On Fri, Dec 21, 2018 at 11:46:16PM +0300, Cyrill Gorcunov wrote:
> Cast to unsigned char is needed in any case. And as far as I remember
> we've been using this multiplication trick for a really long time
> in x86 land. I'm out of sources right now but it should be somewhere
> in assembly libs.

x86 isn't the only CPU. Some CPUs have slow multiplies but fast shifts.
Also loading 0x0101010101010101 into a register may be inefficient on
some CPUs.