[RFC] Statistics of non-ASCII characters in strings

[Ondřej Bílka]

On Tue, Dec 23, 2014 at 03:35:43PM +0100, Florian Weimer wrote:
> On 12/22/2014 03:46 PM, Wilco Dijkstra wrote:
> >Does anyone have statistics of how often strings contain non-ASCII characters? I'm asking because
> >it's feasible to make many string functions faster if they are predominantly ASCII by using a
> >different check for the null byte.
> 
> Why can't you do the equivalent of
> 
>   X = ((X & 0x80) >> 1) | (X & 0x7F);
> 
> before the new check?  Does this lengthen the dependency chain too much?
> 
When string is short and you do not enter loop its best to determine
these exactly. For longer you get considerable savings even by skipping one
operation.