Re: [PATCH v2 0/5] Speed up uNN_chr and uNN_strchr with Boyer-Moore algorithm

[Paolo Bonzini]

On 07/29/2010 06:00 PM, Pádraig Brady wrote:
> On 29/07/10 16:29, Paolo Bonzini wrote:
> >    if (!needle[0])
> >      return haystack;
> >
> >    n = u8_mbtouc(&uc, needle, 4);
          ^^^^^^^^^

u8_strmbtouc here as suggested by Bruno.  u8_strmbtouc also checks 
itself for NULL, and returns zero in that case.

> >    if (uc == 0xfffd&&  n != 3)
> >      return NULL; /* invalid, cannot be incomplete since we pass n=4 */
> >    if (needle[n])
> >      return strstr(haystack, needle);
> >    else
> >      return u8_strchr(haystack, uc); /* inlining would avoid uctomb */
>
> Clever. I missed the 'if (needle[n])' trick.
> Extra clever if the compiler actually avoids the uctomb.

Unfortunately that would be _manual_ inlining, or some #include trick to 
share the code between u8_strchr and u8_strstr.

> I guess Bruno's point is u8_mbtouc is free to access
> the given size in future, if it was changed to vectorize for example.

Right.  Then we should convince him to change the spec before it's too 
late. :)

Paolo